Abstract
A resonator for spin waves, wherein the resonator comprises a stack of material layers arranged on a substrate, a waveguide structure formed in at least one material layer in the stack and configured to propagate a spin wave and to confine a spin wave propagating in a waveguide element of the waveguide structure, such that a spin wave of a selected frequency propagating in the waveguide structure is arranged to resonate in the waveguide structure. The resonator further comprises a control mechanism formed in at least one material layer in the stack and configured to adapt at least one property of the waveguide structure for tuning the resonance frequency of the waveguide structure.
Claims
1. Resonator for spin waves, wherein the resonator comprises: a stack of material layers arranged on a substrate, a waveguide structure formed in at least one material layer in the stack and configured to propagate a spin wave and to confine a spin wave propagating in a waveguide element of the waveguide structure, such that a spin wave of a selected frequency propagating in the waveguide structure is arranged to resonate in the waveguide structure, and a control mechanism formed in at least one material layer in the stack and configured to adapt at least one property of the waveguide structure for tuning the resonance frequency of the waveguide structure.
2. The resonator of claim 1, wherein the control mechanism is encompassed by the waveguide structure.
3. The resonator of claim 1, wherein the waveguide element is formed by a magnetic material configured to propagate a spin wave.
4. The resonator of claim 1, wherein the waveguide structure comprises a reflector arrangement configured to confine a propagating spin wave in the waveguide element by reflection of the spin wave.
5. The resonator of claim 4, wherein the waveguide element extends along a principal axis of spin wave propagation, and the reflector arrangement comprises reflective interfaces at the respective ends of the waveguide element.
6. The resonator of claim 5, wherein the reflector arrangement comprises at least one of a periodic reflector array and a Bragg reflector.
7. The resonator of claim 5, wherein the reflector arrangement comprises at least one non-magnetic medium.
8. The resonator of claim 1, wherein the control mechanism is configured to adapt at least one physical property of the waveguide structure.
9. The resonator of claim 1, wherein the control mechanism is configured to adapt at least one magnetic property of the waveguide structure.
10. The resonator of claim 4, wherein the control mechanism is further configured to control at least one property of the reflector arrangement.
11. The resonator of claim 1, further comprising at least one transducer arrangement coupled to the waveguide structure and configured to generate a spin wave in the waveguide structure, a deformation element configured to change its physical dimensions in response to an electrical actuation, and a magnetostrictive element coupled to the deformation element, wherein a change in physical dimensions of the deformation element in response to the electrical actuation results in a mechanical stress in the magnetostrictive element, resulting in a change in magnetization of the magnetostrictive element and resulting in a generation of a spin wave in the waveguide structure.
12. Resonator arrangement, comprising an array of at least two resonators of claim 1, wherein the waveguide structures and control mechanisms of the at least two resonators are arranged on a common substrate.
13. Filter arrangement for processing at least one signal, the filter arrangement comprising at least one resonator of claim 1, an electrical input port coupled to the at least one resonator, wherein the electrical input port is configured to transmit an input spectrum, s.sub.1, to the at least one resonator, wherein the at least one resonator is configured to generate an output spectrum, s.sub.2, based on a resonance of the spin wave in the waveguide structure resulting from the input spectrum, the filter arrangement further comprising an electrical output port coupled to the at least one resonator, wherein the electrical output port is configured to transmit the output spectrum from the at least one resonator.
14. Method for generating resonance of spin waves using a resonator for spin waves, wherein the resonator comprises: a stack of material layers arranged on a substrate, a waveguide structure formed in at least one material layer in the stack and configured to propagate a spin wave and to confine a spin wave propagating in a waveguide element of the waveguide structure, such that a spin wave of a selected frequency propagating in the waveguide structure is arranged to resonate in the waveguide structure, and a control mechanism formed in at least one material layer in the stack and configured to adapt at least one property of the waveguide structure for tuning the resonance frequency of the waveguide structure, the method comprising the steps of: propagating a spin wave in the waveguide structure and confining the spin wave propagating in the waveguide element of the waveguide structure, such that a spin wave of a selected frequency propagating in the waveguide structure is arranged to resonate in the waveguide structure, and adapting at least one property of the waveguide structure for tuning the resonance frequency of the waveguide structure.
15. Method according to claim 14, the method further comprising the step of: generating a spin wave in the waveguide structure.
16. The resonator of claim 8, wherein the control mechanism is configured to adapt at least one magnetic property of the waveguide structure.
17. The filter arrangement of claim 13, wherein the control mechanism is configured to adapt at least one physical property of the waveguide structure.
18. The filter arrangement of claim 17, wherein the control mechanism is configured to adapt at least one magnetic property of the waveguide structure.
19. The method according to claim 14, wherein the adapting comprises adapting at least one of at least one physical property of the waveguide structure, and at least one magnetic property of the waveguide structure, for tuning the resonance frequency of the waveguide structure.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.
[0045] FIGS. 1a-b are schematic views of a resonator according to exemplifying embodiments of the present invention,
[0046] FIGS. 2a-b are schematic view of spin waves propagating in a resonator according to an exemplifying embodiment of the present invention,
[0047] FIGS. 3a-e are schematic views of resonators according to exemplifying embodiments of the present invention,
[0048] FIG. 4 is a schematic view of a filter arrangement according to an exemplifying embodiment of the present invention,
[0049] FIG. 5 is a schematic flow chart of a method according to an exemplifying embodiment of the present invention, and
[0050] FIGS. 6a-h are schematic views of a control mechanism of a resonator according to exemplifying embodiments of the present invention.
DETAILED DESCRIPTION
[0051] FIG. 1a is a schematic view of a resonator 100 for spin waves according to an exemplifying embodiment of the present invention.
[0052] The resonator 100 comprises a stack of material layers 110 arranged on a substrate 120. It will be appreciated that the substrate 120 may be a semiconductor substrate, and the resonator 100 may hereby be advantageously manufactured using semiconductor fabrication technologies (more in particular, a CMOS compatible processing technology). The resonator 100 may furthermore be monolithically integrated/manufactured above a semiconductor or CMOS circuitry.
[0053] The resonator 100 comprises a waveguide structure 130 formed in at least one material layer in the stack 110. The waveguide structure 130 comprises a waveguide element 150, which may be a film, wire, strip, or the like, which furthermore may comprise a ferromagnetic, ferrimagnetic, antiferromagnetic or ferrite material strip. Hence, embodiments of the present invention are not necessarily limited to ferromagnetic waveguide structures 130, and it will be appreciated that the waveguide structure 130 may comprise substantially any material having magnetic properties suitable for the propagation of spin waves, and the associated quasi-particles called magnons. For example, the waveguide structure 130 may comprise an antiferromagnetic material. The waveguide structure 130 may alternatively comprise a ferromagnetic material, such as ferromagnetic metal based on iron, copper, nickel or alloys thereof, or heterostructures formed from such materials, e.g. NiFe, CoFe, CoNi, CoFeB or CoPt. The waveguide structure 130 may also comprise a ferrite material, e.g. oxides based on Fe, Ba, Y, Sr, Zn and/or Co.
[0054] The waveguide structure 130 may extend longitudinally, having a major longitudinal dimension and a minor transverse dimension in a plane parallel to the substrate 120. For example, the minor transverse dimension may be relatively small such as to allow propagation of spin waves 140 through the waveguide structure 130 along one directional axis, e.g. corresponding to the longitudinal dimension of the waveguide structure 130. It should be noted that the spin wave 140 may also propagate perpendicular to the longitudinal dimension of the waveguide structure 130, i.e. in the direction of the thickness of the waveguide structure 130.
[0055] The waveguide structure 130 may for example be a structure having a width, i.e. in a direction orthogonal to a longitudinal orientation of the waveguide and parallel to the substrate 120, that is less than or equal to 10 μm, e.g. less than or equal to 1 μm, or less than or equal to 750 nm, e.g. in the range of 350 nm to 650 nm, e.g. 500 nm. The waveguide structure 130 may furthermore have a length, e.g. in the longitudinal direction thereof, which is greater than or equal to 5 μm, e.g. greater than or equal to 7.5 μm, e.g. in the range of 8 μm to 30 μm, e.g. in the range of 9 μm to 20 μm, e.g. in the range of 10 μm to 15 μm. Alternatively, the width of the waveguide structure 130 may be in the order of 100 μm, whereas the length may be in the range of 10-20 μm. The waveguide structure 130 may be adapted for conducting spin waves 140 having microwave frequencies, e.g. in the gigahertz range, e.g. higher than or about equal to 1 GHz, higher than or equal to 10 GHz, higher than or equal 5 to 20 GHz, e.g. higher than or equal to 40 GHz, or even higher, e.g. 60 GHz or higher. The present invention is advantageous in that it can be implemented on a micro/nanoscale, e.g. having physical dimensions smaller than the wavelength in free space of an electromagnetic wave in the microwave spectrum.
[0056] The waveguide structure 130 is configured to propagate a spin wave 140 and to confine a spin wave 140 propagating in the waveguide element 150 of the waveguide structure 130, such that a spin wave 140 of a selected frequency propagating in the waveguide structure 130 is arranged to resonate in the waveguide structure 130. Hence, the waveguide structure 130 is configured to provide resonance for the spin wave 140 of a selected frequency by oscillation of the spin wave 140 in the waveguide element 150.
[0057] The resonator 100 comprises a control mechanism 200 formed in at least one material layer in the stack 110. In this example, the control mechanism 200 is provided between the substrate 120 and the waveguide element 130. However, other arrangements are feasible, wherein the control mechanism 200 may be provided in proximity to or in direct physical contact with the waveguide structure 130. For example, the control mechanism 200 may be arranged on top of the waveguide structure 130.
[0058] The control mechanism 200 is configured to adapt at least one property of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130. Hence, the control mechanism 200 is configured to adapt one or more properties of the waveguide structure 130 so as to tune the resonant frequency of the waveguide structure 130. More specifically, the control mechanism 200 may, e.g. by virtue of being arranged in a close vicinity or in physical contact with the waveguide structure 130, influence, adapt and/or adjust one or more physical and/or magnetic properties of the waveguide structure 130 for an adaptation and/or an adjustment of the waveguide structure 130 to the resonant frequency of the spin wave 140. Examples of control mechanisms 200 according to the above-mentioned concepts are presented in FIGS. 6a-h and the associated text. It will be appreciated that the resonator 100 as exemplified in FIG. 1a may be used for both standing spin waves 140 as well as travelling spin waves 140.
[0059] It should be noted that the resonator 100 as shown in FIG. 1a does not indicate any port and/or transducer element. However, resonators comprising such ports and/or transducer elements are further described in FIGS. 3a-e.
[0060] FIG. 1b is a schematic view of a resonator 100 for spin waves according to an exemplifying embodiment of the present invention. It will be appreciated that FIG. 1b has many features in common with the resonator 100 of FIG. 1a, and it is hereby referred to FIG. 1a and the associated text for an increased understanding. Compared to the resonator 100 of FIG. 1a, the resonator 100 in FIG. 1b further comprises a reflector arrangement 300. The waveguide element 150 of the waveguide structure 130 extends along a principal axis of the propagation of the spin wave 140, and the reflector arrangement 300 comprises a reflective interface 310a, 310b at the respective end of the waveguide element 150. The reflector arrangement 300 is configured to confine or detain a spin wave 140 propagating in the waveguide element 150 by reflection of the spin wave 140. The reflector arrangement 300 may comprise a periodic reflective array (Bragg-type reflector) for spin wave reflection. Alternatively, or in combination herewith, the reflector arrangement 300 may comprise a magnetic discontinuity composed of a non-magnetic material e.g., a noble gas, air, or the like, for the purpose of reflecting the incident spin wave 140. In the resonator 100 of FIG. 1b, only standing spin waves 140 of integers n of half the spin wave wavelength λ can exist in the waveguide element 150 of the resonator 100, i.e. n.Math.λ/2. In contrast, in case of travelling spin waves, only travelling spin waves of integers n of the spin wave wavelength λ can exist, i.e. n.Math.λ. Analogously with the resonator 100 of FIG. 1a, the control mechanism 200 of the resonator 100 of FIG. 1b is configured to adapt at least one property of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130.
[0061] FIGS. 2a-b are schematic views of spin waves 140 propagating in a resonator 100 according to an exemplifying embodiment of the present invention.
[0062] In FIG. 2a, an incident spin wave 140a which propagates in the waveguide structure 130 of the resonator 100 of FIG. 1b is reflected at the reflective interface 310a and 310b thereby creating standing waves 140a and 140b. Consequently, a reflected spin wave 140b propagates in the waveguide structure 130. Hence, FIG. 2a shows a standing spin wave in the bulk of the waveguide structure 130, which is reflected by the oppositely arranged reflective interfaces 310a and 310b. The control mechanism 200 of the resonator 100 is configured to adapt at least one property of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130.
[0063] FIG. 2b shows a schematic view of a waveguide element 130, without such a reflector arrangement 310a, 310b, of a resonator according to an exemplifying embodiment. Here, a spin wave 140 travels along a surface of the perimeter of the waveguide structure 130. Hence, compared to the arrangement of FIG. 2a, no reflective interfaces are provided in this embodiment of the resonator. The circumference C of the waveguide structure 130 is C=2L+2H, wherein L is the length of the waveguide structure 130 and H is the height of the waveguide structure 130. It will be appreciated that the spin wave 140 furthermore may travel perpendicular to the direction as indicated in FIG. 2b. Accordingly, the circumference C of the waveguide structure 130 for this propagation of the spin wave 140 is C=2W+2H, wherein W is the width of the waveguide structure 130. The control mechanism of the resonator is configured to control at least one property of the waveguide structure 130 such that the circumference C corresponds to integers n of the spin wave wavelength λ, i.e. C=n.Math.λ. In this way, the control mechanism 200 may tune the resonance frequency of the waveguide structure 130.
[0064] FIGS. 3a-e are schematic views of resonators 100 according to exemplifying embodiments of the present invention. It will be appreciated that the resonators 100 of FIGS. 3a-e have many features in common with the resonators 100 of FIGS. 1a and 1b, and it is hereby referred to those figures and the associated text for an increased understanding.
[0065] Compared to the resonator 100 of FIG. 1a, the resonator 100 in FIG. 3a further comprises at least one schematically indicated input/output (I/O) or port 510a. In one embodiment, the port 510a may comprise a stack of elements and/or layers, and may alternatively be referred to as a two-terminal or transducer element. The terminal 510a is configured to convert an (electrical) input signal s.sub.1 into a magnetic signal carried by the spin wave 140. Furthermore, the resonator 100 is configured to tune the resonance frequency of the waveguide structure 130 via the control mechanism 200. In this way, the resonator 100 may generate an output signal s.sub.2 and read the output signal s.sub.2 via the terminal 510a. In case of a resonator having one I/O port, the output signal s.sub.2 will be maximal at the resonance frequency of the spin wave 140, e.g. as observed in the impedance seen by the port 510a. It will be appreciated that the resonator 100 is operable for both standing spin waves 140 as well as for travelling spin waves 140.
[0066] FIG. 3b is an exemplifying embodiment of the resonator 100 of FIG. 3a. Here, the input/output (I/O) or port 510a comprises a stack of elements and/or layers 410a. The port 510a comprises, in a top-down direction, an electrode 420a, a deformation element 430a configured to change its physical dimensions in response to an electrical (alternating) actuation, and a magnetostrictive element 440a coupled to the deformation element 430a. Alternatively, the deformation element 430a may be provided between (i.e. sandwiched) two electrode layers, i.e. the terminals of two I/O ports 510a, 510b (not shown). As yet another alternative, the electrode 420a may be provided under the deformation element 430a. For example, the electrode layer 420a may comprise two electrodes, and the deformation element 430a may be sandwiched between the two electrodes. The magnetostrictive element 440a may comprise Terfenol-D, Tb.sub.xDy.sub.1−xFe.sub.2; Galifenol, Ga.sub.xFe.sub.1−x; Co; Ni; a Heusler alloy or a combination thereof, which is advantageous in that well known and easily available materials may be used in the magnetostrictive element 430a.
[0067] The electrode 420a, the deformation element 430a and the magnetostrictive element 440a may be provided in (close) proximity to or in direct physical contact with the neighbouring layer of the port 510a. The deformation element 430a is advantageously arranged in direct physical contact with the magnetostrictive element 440a.
[0068] The port 510a is configured to convert an input signal s.sub.1 into a magnetic signal carried by a spin wave 140. More specifically, the spin wave 140 may be generated by the port 510a in the following way: an actuation signal (e.g. a voltage) supplied to the port 510a via the electrode 420a results in a change of the physical dimensions of the deformation element 430a. Consequently, there is a mechanical deformation or mechanical stress induced in the associated magnetostrictive element 440a, resulting in a change in magnetization of the magnetostrictive element 440a, which in turn may result in a generation of a spin wave 140 in the waveguide structure 130 of the resonator 100. The resonator 100 may further comprise a control mechanism 200 according to any one of the previously described embodiments. Hence, the control mechanism 200 is configured to adapt at least one property of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130 generated by the resonator 100. It will be appreciated that the resonator 100 is operable for both standing spin waves 140 as well as for travelling spin waves 140.
[0069] FIG. 3c is a schematic view of a resonator 100 comprising a transducer arrangement 400 as input/output (I/O) port according to an exemplifying embodiment of the present invention. The transducer arrangement 400 is coupled to the waveguide structure 130 and configured to generate a spin wave 140 in the waveguide structure 130. In this example, the transducer arrangement 400 comprises two stacks 410a, 410b arranged on the waveguide structure 130 and spaced apart along the longitudinal direction of the waveguide structure 130. However, it should be noted that the transducer arrangement 400, as an alternative, may be provided with a single, unique stack, as illustrated in FIG. 3b. Each of the stacks 410a, 410b comprises, in a top-down direction, an electrode 420a,b, a deformation element 430a,b configured to change its physical dimensions in response to an electrical (alternating) actuation, and a magnetostrictive element 440a,b coupled to the deformation element 430a,b. Alternatively, the deformation element 430a,b may be provided between (i.e. sandwiched) two electrode layers.
[0070] The electrodes 420a,b, the deformation elements 430a,b, and the magnetostrictive elements 440a,b may be provided in (close) proximity to or in direct physical contact with the neighbouring layer of the respective stack 410a, 410b. The deformation elements 430a,b are advantageously arranged in direct physical contact with the magnetostrictive elements 440a,b.
[0071] It will be appreciated that one of the two port stacks 410a, 410b as exemplified may be configured to generate a spin wave, whereas the other of the two stacks 410a, 410b may be configured to detect the generated spin wave. The two stacks 410a, 410b may hereby constitute ports, e.g. an input port 410a and an output port 410b (or vice versa). During operation of the transducer arrangement 400, an actuation signal supplied to one of the electrodes 420a,b results in a change of the physical dimensions of the associated deformation element 430a,b. Consequently, there is a mechanical deformation or mechanical stress induced in the associated magnetostrictive element 440a,b, resulting in a change in magnetization of the magnetostrictive element 440a,b, which in turn results in a generation of a spin wave 140 in the waveguide structure 130. The resonator 100 further comprises a control mechanism 200 according to any one of the previously described embodiments. The control mechanism 200 is configured to adapt at least one property of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130 generated by the transducer arrangement 400. The spin wave 140, which may be generated by one of the two stacks 410a, 410b, may analogously be detected by one of the two stacks 410a, 410b.
[0072] Although not shown in FIG. 3c, there may alternatively be an array of at least two resonators 100 comprising a transducer arrangement 400, wherein the waveguide structures 130 and control mechanisms 200 of the at least two resonators 100 are arranged on a common substrate 120.
[0073] FIG. 3d is a schematic view of a filter arrangement 500 according to an exemplifying embodiment of the present invention. The filter arrangement 500 comprises a resonator 100 of any one of the preceding embodiments. As the structure, arrangement and/or function of the resonator 100 is the same or similar to that or those already described in the previous text and/or figures, it is hereby referred to that or those sections. The filter arrangement 500 further comprises input/output (I/O) ports which are exemplified as an electrical input port 510a and an electrical output port 510b which are coupled to the resonator 100, e.g. as exemplified in one or more of FIGS. 3a-c. The electrical input port 510a and the electrical output port 510b are arranged on the waveguide structure 130 and are spaced apart from each other along the longitudinal direction of the waveguide structure 130. The electrical input port 510a may comprise an input transducer for converting an input signal s.sub.1 into a spin wave 140 having substantially the same, e.g. having the same, spectrum as the input signal s.sub.1. Analogously, the electrical output port 510b may comprise an output transducer for converting the filtered spin wave 140 into an output signal s.sub.2 having substantially the same, e.g. having the same, spectrum as the filtered spin wave 140. The input transducer and/or the output transducer may, for example, comprise a magneto-electric transducer and/or a co-planar waveguide antenna. The electrical input port 510a is configured to transmit the input signal s.sub.1 having a frequency band to the resonator 100. The resonator 100 is configured to filter the input signal s.sub.1 based on a resonance of the spin wave 140 in the waveguide structure 130. The filtering of the resonator 100 results in the output signal s.sub.2 having a frequency band, wherein the control mechanism 200 of the resonator 100 is configured to adapt the waveguide structure 130 for its tuning of the resonance frequency. The electrical output port 510b of the filter arrangement 500 is configured to transmit the output signal s.sub.2 from the resonator 100.
[0074] FIG. 3e is a schematic view of a filter arrangement 500 according to an exemplifying embodiment of the present invention. The filter arrangement 500 is similar to that described in FIG. 3d, and it is hereby referred to that figure and associated text. Compared to the filter arrangement 500 in FIG. 3d, the filter arrangement 500 in FIG. 3e further comprises a reflector arrangement according to one or more of the previously described embodiments. The filter arrangement 500 is hereby applicable for standing spin waves. The reflector arrangement comprises a reflective interface 310a, 310b at the respective end of the waveguide element 130. The electrical input port 510a is configured to transmit an input signal s.sub.1 to the resonator 100. The resonator 100 is configured to filter the input signal s.sub.1 based on a resonance of the spin wave 140 in the waveguide structure 130. The filtering of the resonator 100 results in an output spectrum signal s.sub.2, wherein the control mechanism 200 of the resonator 100 is configured to adapt the waveguide structure 130 for its tuning of the resonance frequency. The electrical output port 510b of the filter arrangement 500 is configured to transmit the output spectrum signal s.sub.2 from the resonator 100.
[0075] FIG. 4 is a schematic view of a filter array 550 comprising a plurality of schematically indicated resonators 500a-c according to one or more of the previously described embodiments. It should be noted that the number of resonators 500a-c is arbitrary, and that there may be more or fewer resonators in the filter array 550. The resonators 500a-c may be combined in substantially any desired configuration such that the desired transfer function of the filter array 550 is obtained. For example, the filter array 550 may be designed as a band-pass filter by connecting a plurality of resonators 500a-c. For example, the filter array 550 may be designed as a high-pass filter by connecting a plurality of resonators 500a-c of high-pass type. In this way, a high-order high-pass filter may be obtained. As yet another alternative, the filter array 550 may comprise a first plurality of resonators which may constitute a low-pass filter, wherein the first plurality of resonators may be arranged in parallel with a second plurality of resonators which, in contrast, may constitute a high-pass filter.
[0076] FIG. 5 is a schematic flow chart of a method 600 for generating resonance of spin waves having selected frequency using a resonator according to the first aspect of the present invention. The method 600 comprises the step of generating and propagating 610 a spin wave in the waveguide structure and confining 620 the spin wave propagating in the waveguide element of the waveguide structure, such that a spin wave of a selected frequency propagating in the waveguide structure is arranged to resonate in the waveguide structure. The method further comprises the step of adapting 630 at least one property of the waveguide structure for tuning the resonance frequency of the spin wave resonator (or waveguide structure). Optionally, the method comprises generating a spin wave in the waveguide structure prior to controlling the resonance of the waveguide structure to determine the resonance frequency.
[0077] FIGS. 6a-d are schematic views of control mechanisms 200 of a resonator according to exemplifying embodiments of the present invention. Generally, in case a signal (e.g., a voltage or a current) or power is supplied to the control mechanism(s) in the following examples, it is typically a signal that is constant for a longer period of time in order to keep the resonance frequency fixed during that period.
[0078] In FIG. 6a, the control mechanism 200 is formed in a material layer of a stack, e.g. as shown in FIGS. 1a-b and/or FIGS. 3a-e. The control mechanism 200 comprises an antenna-like structure, comprising a coil 210 through which a current I is arranged to pass. It will be appreciated that the coil 210 may have substantially any shape, e.g. a spiral shape or a simple wire. During operation of the control mechanism 200, the current I in the coil 210 creates a magnetic field in the material layer around which the control mechanism 200 is formed, which in its turn influences the waveguide element 150 of the waveguide structure 130 arranged on the material layer of the control mechanism 200. Hence, the control mechanism 200 is hereby configured to adapt at least one magnetic property (e.g., the magnetisation of the waveguide material) of the waveguide structure 130 for tuning the resonance frequency of the spin wave 140 in the resonator 100.
[0079] FIGS. 6b-d show examples wherein the control mechanism 200 may be configured to adapt at least one physical property of the waveguide structure 130 for tuning the resonance of the spin wave 140 in the resonator 100. The control mechanism 200 may be formed in a material layer of a stack, e.g. as shown in FIGS. 1a-b and/or FIGS. 3a-e.
[0080] In FIG. 6b, the control mechanism 200 is of thermomechanical type, and comprises a heating element 230. It will be appreciated that the heating element 230 may constitute or comprise substantially any element or device for providing an increase in temperature, e.g. a heating resistor or resistive coil. During operation of the control mechanism 200, the heating element 230 may transfer heat to the waveguide structure 130 being in thermal contact with the heating element 230, e.g. by direct physical contact between the material layer of the control mechanism 200 and the waveguide structure 130. Consequently, there may be a thermal expansion (or retraction) which may change the dimensions of the waveguide structure 130 for tuning the resonance of the waveguide structure 130 in the resonator 100. Furthermore, during operation of the control mechanism 200, the heat from the heating element 230 will cause a mechanical stress in the waveguide structure 130.
[0081] In FIG. 6c, the control mechanism 200 is of thermomechanical type, and involves optical heating. More specifically, the control mechanism 200 comprises a photon source 250, e.g. an (optical) light source. During operation, the photon source 250 of the control mechanism 200 may radiate the adjacently arranged waveguide structure 130 with photons. The light is absorbed in the waveguide structure 130 and causes thermomechanical stress in the waveguide structure 130. The photons radiated to the waveguide structure 130 may influence one or more physical and/or magnetic properties of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130 of the resonator.
[0082] In FIG. 6d, the control mechanism 200 is arranged as a stack of material layers. The control mechanism 200 comprises, in a top-down direction, a first electrode 230a, a deformation element 220, a second electrode 230b, and a waveguide structure 130. The deformation element 220 of the control mechanism 200 is configured to change its physical dimensions in response to an electrical actuation signal. For example, the deformation element 220 may comprise a piezoelectric element. The piezoelectric element may comprise PbZrTiO.sub.3, PZT; PbMgN-bO.sub.x—PbTiO.sub.x, PMN-PT; BaTiO.sub.3, BTO; SrBiTaO.sub.x, SBT; AlN; GaN; LiNbO.sub.3, LNO; ZnO; (K,Na)NbO.sub.x, KNN; orthorhombic HfO.sub.2 or a combination thereof. During operation of the control mechanism 200, an electrical signal (voltage or current) provided to the electrodes 230a,b deforms the deformation element 220, which in turn deforms the waveguide structure 130. Hence, mechanical stress is exerted on the waveguide structure 130. One or more physical (geometrical) properties of the waveguide structure 130 may be adapted and/or adjusted, e.g. the length, width, etc. Consequently, the resonance frequency of the waveguide structure 130 may hereby be tuned.
[0083] In FIG. 6e, the control mechanism 200 is arranged as a stack of material layers, similar to the arrangement as shown in FIG. 6d. The control mechanism 200 comprises, in a top-down direction, a first electrode 230a, a deformation element 220, a second electrode 230b, a magnetostrictive layer 440a, and a waveguide structure 130.
[0084] The electrodes 230a,b, the waveguide structure 130, the deformation element 220 and the magnetostrictive layer 440a may be provided in (close) proximity to or in direct physical contact with the neighbouring layers.
[0085] During operation of the control mechanism 200, an actuation signal (e.g. a voltage) supplied to one of the electrodes 230a,b results in a change of the physical dimensions of the associated deformation element 220. Consequently, there is a mechanical deformation or mechanical stress induced in the associated magnetostrictive element 440a, which in turn results in the creation of a changing magnetic field applied to the waveguide structure 130. Consequently, the resonance frequency of the waveguide structure 130 of the resonator may hereby be tuned.
[0086] FIG. 6f shows a schematic view of a control mechanism 200 of a resonator according to an exemplifying embodiment of the present invention and according to the principle as shown in FIG. 2b. Here, the resonator comprises a plurality of waveguide structures 130a-c arranged longitudinally in series. It should be noted that the number and/or size of the waveguide structures 130a-c may be arbitrary. The control mechanism 200 of the resonator is configured to determine which waveguide structure(s) of the plurality of waveguide structures 130a-c to use in the propagation of the spin wave 140 in the resonator. For example, the control mechanism 200 may be configured to determine that the waveguide structure 130a should be used for the propagation of the spin wave 140. The spin wave 140 may hereby travel along a surface of the perimeter of the waveguide structure 130a. The circumference C1 of the waveguide structure 130a is C1=2L1+2H1, wherein L1 is the length of the waveguide structure 130a and H1 is the height of the waveguide structure 130a. The circumference C1 corresponds to integers n of the spin wave wavelength λ, i.e. C1=n.Math.λ. Alternatively, the control mechanism 200 may be configured to determine that the waveguide structures 130a and 130b should be used for the propagation of the spin wave 140b. The spin wave 140b may hereby travel along a surface of the perimeter of the waveguide structures 130a and 130b. The circumference C2 of the waveguide structure 130 is C2=2L1+2L2+H1+H2, wherein L1 is the length of the waveguide structure 130a, L2 is the length of the waveguide structure 130b, H1 is the height of the waveguide structure 130a and H2 is the height of the waveguide structure 130b. The control mechanism 200 is configured to control at least one property of the waveguide structure 130 such that the circumference C2 corresponds to integers n of the spin wave wavelength λ, i.e. C2=n.Math.λ. In this way, the control mechanism 200 may tune the resonance frequency of the waveguide structure 130. Analogously, and as yet another alternative, the control mechanism 200 may be configured to determine that the waveguide structures 130a-c should be used for the propagation of the spin wave 140b, whereby the circumference C3 along the waveguide structure for the travelling spin wave is C3=2L1+2L2+2L3+H1+H3.
[0087] FIG. 6g shows a schematic top view of a waveguide structure 130 of a resonator according to an exemplifying embodiment of the present invention. The resonator comprises a first port 510a, which is arranged at a first position 511 on the waveguide structure 130. The resonator further comprises a second port 510b arranged at a second position 512a-c of the waveguide structure 130, wherein the distance between the first port 510a and the second port 510b constitutes an effective predetermined distance L1, L2 or L3. According to this example, the control mechanism of the resonator is configured to select a waveguide structure 130 with an appropriate length. For example, a first waveguide structure 130 may have the effective length L1 between the first terminal 510a and a second port 510b arranged at the second position 512a. Analogously, a second (or third) waveguide structure 130 may have the effective length L2 (or L3) between the first port 510a and a second port 510b arranged at the second position 512b (or the third position 512c). It should be noted that the number of waveguide lengths is arbitrary, and that the three lengths of the waveguide structure between the positions 511 and the positions 512a-c, respectively, have been indicated for illustrative purposes only. The control mechanism (not shown) of the resonator may hereby be configured to select which waveguide structure 130 to use for selecting the effective length of the waveguide structure 130 between the first port 510a and the second port 510b. Consequently, the control mechanism may adapt the effective length of the waveguide structure for tuning the resonance frequency of the waveguide structure of the resonator.
[0088] FIG. 6h shows yet another embodiment of the resonator 100 according to an example. In accordance with one or more of the previously described embodiments, the resonator 100 is arranged as a stack 110 of material layers arranged on the substrate 120. The waveguide structure 130 is formed in at least one material layer in the stack and configured to propagate a spin wave 140 and to confine the spin wave 140 propagating in a waveguide element of the waveguide structure 130. The control mechanism 200 is arranged between the substrate 120 and the waveguide element 150. Furthermore, a dielectric layer 155 is arranged between the control mechanism 200 and the waveguide structure 130. The control mechanism 200 is configured to inject a charge into the waveguide structure 130 for adapting the waveguide structure 130 such that the resonance frequency of the waveguide structure of the resonator may be tuned.
[0089] It should be noted that FIGS. 6a-h merely show a few examples for influencing, adapting and/or adjusting the waveguide structure 130 via the control structure 200 of the resonator 100 in order to tune the resonance frequency of the waveguide structure 130. Hence, there may be numerous alternatives in the design, configuration and/or operation of the control mechanism 200 for adapting one or more physical (geometrical) and/or magnetic properties of the waveguide structure 130 for tuning the resonance frequency of the waveguide structure 130.
[0090] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, it will be appreciated that the figures are merely schematic views of devices according to embodiments of the present invention. Hence, the resonator, the elements and/or components of the resonator, etc., may have different dimensions, shapes and/or sizes than those depicted and/or described. For example, one or more layers may be thicker or thinner than what is exemplified in the figures, the stack(s) may have other shapes, depths, etc., than that/those depicted. Moreover, the order of the layer(s) in the stack of material layers may be different than that shown. For example, the control mechanism 200, which is shown to be arranged between the substrate 120 and the waveguide structure 130, may alternatively be arranged on top of the waveguide structure 130. Furthermore, it will be appreciated that the techniques related to the various configurations and/or operations of the control mechanism may be different from those disclosed.
