A magnetic field detection sensor includes a magneto-impedance element configured to make use of the magneto-impedance effect, and a negative-feedback bias coil configured to apply a bias magnetic field to the magneto-impedance element. The magnetic field detection sensor is configured to detect an external magnetic field based on an output obtained by applying an alternating-current to the magneto-impedance element. The magneto-impedance element includes a non-magnetic substrate, and a magnetic thin-film that is provided on a surface of the non-magnetic substrate. The magnetic field detecting direction matches the longitudinal direction of the magneto-impedance element, and the magnetic thin-film is configured to have a magnetic anisotropy such that a direction of an axis of easy magnetization thereof matches the magnetic field detecting direction.

The magnetic field detector includes an x-axis magnetic sensor, a y-axis magnetic sensor, and a z-axis magnetic sensor for detecting magnetic field components in three orthogonal axis directions. Each of the magnetic sensors includes a magnetic impedance element having an impedance that varies in accordance with an ambient magnetic field and an output circuit configured to output a magnetic field detection value that varies in accordance with the impedance of the magnetic impedance element. The magnetic field detector includes an oscillator configured to supply a common drive signal to the magnetic impedance element of each of the magnetic sensors, wherein each of the magnetic sensors outputs, in response to the drive signal, the magnetic field detection value from the output circuit.

A magnetic field detecting device which comprises a magnetic impedance sensor including a magnetic impedance element 1 in which a pulse electrical current or a high frequency electrical current is applied from an oscillator 2 to an amorphous wire 10 and an alternate current or AC damped oscillation voltage, which is induced in a detecting coil 11 wound around the amorphous wire 10 and has a magnitude corresponding to an external magnetic field, is output, and an arbitrary magnetic field is applied to the amorphous wire by means of the magnetic field generated on the detecting coil 11 energized by connecting the detecting coil 11 to a voltage source or to a current source E through an impedance network 3 comprising of a resistor R or a coil L or a condenser C or comprising a combination of the resistor R, the coil L, and the condenser C.

A magnetic field measurement device capable of accurate measurement of a magnetic field even after a sensitivity of an MI sensor varies is provided. A magnetic field measurement device (1) includes an MI sensor (2) and a sensitivity calculation means (3). The MI sensor (2) includes a magneto-sensitive body (20), a detection coil (21) and a magnetic field generation coil (22) that generates a magnetic field upon energization. The sensitivity calculation means (3) varies a current flowing in the magnetic field generation coil (22) in a state where an outside-sensor magnetic field H.sub.O acting on the magneto-sensitive body (20) from outside the MI sensor (2) is constant. Consequently, the magnetic field acting on the magneto-sensitive body (20) is varied to calculate a sensitivity a by dividing a variation in an output voltage of the detection coil (21) by a variation in the magnetic field acting on the magneto-sensitive body (20).

Sensitivity of a magnetic sensor using the magnetic impedance effect is improved. A magnetic sensor includes: a non-magnetic substrate; a sensitive element provided on the substrate, including a soft magnetic material, having a longitudinal direction and a short direction, provided with uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and sensing a magnetic field by a magnetic impedance effect; and a protrusion part including a soft magnetic material and protruding from an end portion in the longitudinal direction of the sensitive element.

In a magnetic sensor using sensitive circuits sensing magnetic fields by the magnetic impedance effect, a sensitivity-to-noise ratio is improved. A magnetic sensor 10 includes: a sensitive circuit 12A including sensitive parts sensing magnetic fields by magnetic impedance effect; and a sensitive circuit 12B including sensitive parts sensing magnetic fields by magnetic impedance effect, wherein at least a part of current paths of the sensitive circuit 12A and at least a part of current paths of the sensitive circuit 12B overlap in a plan view, and one end portion of the sensitive circuit 12A and one end portion of the sensitive circuit 12B are electrically connected.

A magnetic sensor 10 includes: a non-magnetic substrate 11; a sensitive circuit 12 provided on a surface of the substrate 11 and including a sensitive part 121 sensing a magnetic field by a magnetic impedance effect; a terminal part 13a and a terminal part 13b connected to respective both end portions of the sensitive circuit 12; and a conductive returning member with one end portion being connected to the terminal part 13a, the returning member returning back toward the terminal part 13b.

A magnetic sensor 1 includes: a non-magnetic substrate 10; and a sensitive element 30 disposed on the substrate 10. The sensitive element 30 has a longitudinal direction and a transverse direction and has a uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction. The sensitive element 30 is configured to sense a magnetic field by a magnetic impedance effect. The sensitive element 30 includes a soft magnetic material layer 101 made of an amorphous alloy based on Co and having a saturation magnetization of greater than or equal to 300 emu/cc and less than or equal to 650 emu/cc.

A magnetic measurement apparatus includes a concentrating structure and a magnetic sensor. The concentrating structure includes a band portion and a plurality of protruding portions. The band portion is configured to concentrate a magnetic flux from a subject. The plurality of protruding portions are configured to transmit the concentrated magnetic flux to a magnetic sensor. The magnetic sensor is magnetically connected between two opposing protruding portions.

A magnetic sensor comprises a magnetic material portion; an excitation portion; and a magnetic detection portion, the magnetic sensor detecting a magnetic field by the magnetic detection portion detecting a detection magnetic field generated due to magnetic moments of the magnetic material portion. The excitation portion is configured to include a conductive material formed into an elongated shape, the magnetic material portion is a soft magnetic film formed on a surface of the conductive material, and the magnetic moments of the magnetic material portion are oriented along circumferential directions of the conductive material orthogonal to a longitudinal direction of the conductive material such that the magnetic moments directed to one of the circumferential directions and the magnetic moments direction in another circumferential direction opposite to the one circumferential direction are distributed in substantially equal amounts.