A manganese-zinc ferrite with a high magnetic permeability at negative temperature and low loss at high temperature consists of Fe.sub.2O.sub.3, MnO and ZnO, and additives consisting of CaCO.sub.3, ZrO.sub.2, Co.sub.2O.sub.3 and SnO.sub.2 are also added. A method for preparing the manganese-zinc ferrite is further provided. According to the method, by reasonably adjusting a ratio of Mn to Zn to Fe and appropriately increasing the content of Co in the additives, a manganese-zinc ferrite material with both a high magnetic permeability and low loss at about −20° C. and low loss at 120-140° C. is obtained. The manganese-zinc ferrite material has two loss valleys at about −20° C. and about 100° C. in a temperature range of −30° C. to 140° C., which expands the application range of the manganese-zinc ferrite material.

A ferrite sintered magnet comprising an M type Sr ferrite having a hexagonal structure as a main phase, wherein the ferrite sintered magnet comprises La and Co, a content of B is 0.005 to 0.9% by mass in terms of B.sub.2O.sub.3, a content of Zn is 0.01 to 1.2% by mass in terms of ZnO, and the ferrite sintered magnet satisfies [La]/[Zn]≤0.79 and [Co]/[Zn]≤0.67 when an atomic concentration of La is represented by [La], an atomic concentration of Co is represented by [Co], and an atomic concentration of Zn is represented by [Zn].

A ferrite sintered magnet comprising an M type Sr ferrite having a hexagonal structure as a main phase, wherein the ferrite sintered magnet comprises La and Co, a content of B is 0.005 to 0.9% by mass in terms of B.sub.2O.sub.3, a content of Zn is 0.01 to 1.2% by mass in terms of ZnO, and the ferrite sintered magnet satisfies [La]/[Zn]≤0.79 and [Co]/[Zn]≤0.67 when an atomic concentration of La is represented by [La], an atomic concentration of Co is represented by [Co], and an atomic concentration of Zn is represented by [Zn].

A device and method for absorbing electromagnetic waves can include a honeycomb sheet formed by a plurality of interconnected hexagon cells arranged in rows. The hexagon cells are made up of sidewalls, each sidewall formed by two surfaces that converge at a top of the sidewall and diverge from the top to a bottom of the sidewall such that a thickness of the sidewalls increases from top to bottom and an angle forms between the two surfaces at the top of the sidewall. In an example, the angle is about 8 degrees. The honeycomb sheet can be coated with a magnetic, composite coating to increase electromagnetic shielding. An example coating includes magnetic multi-granular nanoclusters (MGNC) and multi-walled carbon nanotubes (MWCNT). A base layer can be attached to the honeycomb sheet for mechanical stability and additional absorption. The device is suitable for radar absorbing materials (RAM) for aerospace and military applications.

A device and method for absorbing electromagnetic waves can include a honeycomb sheet formed by a plurality of interconnected hexagon cells arranged in rows. The hexagon cells are made up of sidewalls, each sidewall formed by two surfaces that converge at a top of the sidewall and diverge from the top to a bottom of the sidewall such that a thickness of the sidewalls increases from top to bottom and an angle forms between the two surfaces at the top of the sidewall. In an example, the angle is about 8 degrees. The honeycomb sheet can be coated with a magnetic, composite coating to increase electromagnetic shielding. An example coating includes magnetic multi-granular nanoclusters (MGNC) and multi-walled carbon nanotubes (MWCNT). A base layer can be attached to the honeycomb sheet for mechanical stability and additional absorption. The device is suitable for radar absorbing materials (RAM) for aerospace and military applications.

This ferrite magnet has a magnetoplumbite structure and is characterized in that, when representing the composition ratios of the total of each metal element A, R, Fe and Me with expression (1) A.sub.1-xR.sub.x(Fe.sub.12-yMe.sub.y).sub.z, the Fe.sup.2+ content (m) in the ferrite magnet is greater than 0.1 mass % and less than 5.4 mass % (in expression (1), A is at least one element selected from Sr, Ba, Ca and Pb; R is at least one element selected from the rare-earth elements (including Y) and Bi, and includes at least La, and Me is Co, or Co and Zn). The invention makes it possible to achieve a ferrite magnet with increased Br.

This ferrite magnet has a magnetoplumbite structure and is characterized in that, when representing the composition ratios of the total of each metal element A, R, Fe and Me with expression (1) A.sub.1-xR.sub.x(Fe.sub.12-yMe.sub.y).sub.z, the Fe.sup.2+ content (m) in the ferrite magnet is greater than 0.1 mass % and less than 5.4 mass % (in expression (1), A is at least one element selected from Sr, Ba, Ca and Pb; R is at least one element selected from the rare-earth elements (including Y) and Bi, and includes at least La, and Me is Co, or Co and Zn). The invention makes it possible to achieve a ferrite magnet with increased Br.

Disclosed herein are embodiments of low temperature co-fireable scheelite materials which can be used in combination with high dielectric materials, such as nickel zinc ferrite, to form composite structures, in particular for isolators and circulators for radiofrequency components. In some embodiments, the scheelite material can include aluminum oxide for temperature expansion regulation.

In an aspect, a Co.sub.2Z ferrite has the formula: (Ba.sub.1-xSr.sub.x).sub.3Co.sub.2+yM.sub.yFe.sub.24-2y-zO.sub.41. M is at least one of Mo, Ir, or Ru. The variable x can be 0 to 0.8, or 0.1 to 0.8. The variable y can be 0 to 0.8, or 0.01 to 0.8. The variable z can be −2 to 2. The Co.sub.2Z ferrite can have an average grain size of 5 to 100 nanometers, or 30 to 80, or 10 to 40 nanometers as measured using at least one of transmission electron microscopy, field emission scanning electron microscopy, or x-ray diffraction.

A method for improving the Bs of an MnZn power ferrite material by moving the valley point includes the following steps: 1) mixing Fe.sub.2O.sub.3, MnO and ZnO, and performing primary sanding; 2) adding glue, performing spraying and granulating, and then performing pre-sintering to obtain a pre-sintered material; 3) adding additives to the pre-sintered material, and performing secondary sanding; and 4) adding glue to the secondary sanded material, performing spraying and granulating, pressing into a standard ring, and then performing sintering. The method controls and moves the valley point, reduces loss and improves the Bs of a material by controlling the Fe.sub.2O.sub.3 content and the Co.sub.2O.sub.3 content, and the method is relatively simple and suitable for industrialization.