Magnetic material, and memory and sensor using same

Abstract

A magnetic material composed of ε-InxFe2-xO3 (wherein 0

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows XRD patterns of In-containing ε-Fe₂O₃ crystals according to the present invention, and of ε-Fe₂O₃.

FIG. 2 shows curves of magnetization measured at various temperatures, in an external magnetic field of 1000 Oe (7.96×10⁴ A/m) of samples of powder particles of the In-containing ε-Fe₂O₃ of the present invention, and of ε-Fe₂O₃.

FIG. 3 are magnetization hysteresis loops of samples of In-containing ε-Fe₂O₃ of the present invention, measured at 200 K and 150 K.

FIG. 4 (a) is a TEM image of In-containing ε-Fe₂O₃ crystals of the present invention.

FIG. 4 (b) is a TEM image of other In-containing ε-Fe₂O₃ crystals of the invention.

FIG. 4 (c) is a TEM image of ε-Fe₂O₃ crystals.

FIG. 5 shows curves of magnetization versus temperature dependency of the complex dielectric constant of In-containing ε-Fe₂O₃ (ε-In_0.19Fe_1.81O₃) of the invention, and of ε-Fe₂O₃.

FIG. 6 is a diagram of a capacitor used for measurements.

FIG. 7 shows curves of dependency of external magnetic field ε′ (at 155 K and 100 kHz) and (magnetization M)²—magnetic field in respect of In-containing ε-Fe₂O₃ (ε-In_0.19Fe_1.81O₃) of the invention.

Claims

1. A magnetic material composed of ε-InxFe2-xO3 (wherein 0<x≦0.30) in which In is substituted for a portion of the Fe sites of the ε-Fe2O3 crystal, that has the same space group as that of an ε-Fe2O3 crystal.

2. The magnetic material according to claim 1, wherein a magnetic phase transition temperature thereof is lower than a magnetic phase transition temperature of the ε-Fe2O3.

3. The magnetic material according to claim 1, wherein a spin reorientation temperature thereof is higher than a spin reorientation temperature of the ε-Fe2O3.

4. The magnetic material according to claim 1, comprised of microparticles having a single domain structure.

5. The magnetic material according to claim 1, comprised of microparticles having a particle diameter along the long axis of the particles, as measured from a transmission electron microscope image, that is from 5 to 200 nm.

6. A magnetic layer of a magnetic recording medium comprised of microparticles of the magnetic material of claim 1, each having a particle diameter along the axis of the particles, as measured from a transmission electron microscope image, that is from 5 to 200 nm, being each affixed to a particle site on a substrate.

7. A magnetic layer of a magnetic recording medium comprised of microparticles of the magnetic material of claim 1, each having a particle diameter along the long axis of the particles, as measured from a transmission electron microscope image, that is from 5 to 200 nm, being each affixed to a particle site on a substrate with the easy axis of magnetization of the particles at each site oriented in a prescribed direction.

8. The magnetic material according to claim 1, wherein a peak temperature of an imaginary part of a complex dielectric constant thereof is higher than that of ε-Fe2O3.

9. A magnetic memory having a magnetic layer comprised of particles of the magnetic material of claim 1 affixed to a substrate, wherein information is recorded on the magnetic layer using a magnetization method in which the magnetic material constituting the magnetic layer is magnetized at a process step of a temperature being lowered from a higher side to a lower side of its magnetic phase transition temperature.

10. A temperature sensor comprising the magnetic material of claim 1 and means for measuring a magnetization intensity of the material, which detects temperature changes relative to the spin reorientation temperature of the material, using the material's characteristics that the magnetic properties are changed drastically at the spin reorientation temperature.

11. The magnetic material according to claim 2, wherein a spin reorientation temperature thereof is higher than a spin reorientation temperature of the ε-Fe2O3.