Magnetic iron oxide nanopowder and process for producing the same

Patent metadata

Field	Value
Publication number	US-10099941-B2
Application number	US-201515318783-A
Country	US
Kind code	B2
Filing date	Jun 18, 2015
Priority date	Jun 18, 2014
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A magnetic σ-form iron oxide nanopowder is a novel magnetic iron oxide nanopowder having magnetic polarization and spontaneous electric polarization and having physical properties similar to those of half-metals; and a process produces the magnetic nanopowder. The magnetic powder has a composition represented by Fe 2 O 3 and has a crystal structure belonging to the monoclinic system.

First claim

The invention claimed is:

1. A magnetic powder having a composition is Fe 2 O 3 , and a Fe coordination site of a pentacoordinated structure in a crystal structure.

2. The magnetic powder according to claim 1 , wherein the magnetic powder includes a magnetic polarization and a spontaneous electric polarization at a room temperature, and an angle formed by the magnetic polarization with respect to the spontaneous electric polarization takes a value between 0° and 90°.

3. The magnetic powder according to claim 1 , wherein only circularly polarized excitation of one side of right and left circularly polarized excitations can be enabled in a near infrared region from a visible region.

4. The magnetic powder according to claim 1 , wherein an energy difference between right and left circularly polarized lights is 0.5 eV or more, and a lower energy value of the right and left circularly polarized energies is 1.5 eV or less.

5. The magnetic powder according to claim 1 , wherein the crystal structure belongs to a monoclinic system.

6. A method for producing the magnetic powder according to claim 1 , to obtain magnetic σ-form iron oxide nanopowder by using β-FeO(OH) (iron oxide hydroxide (III)) nano-particle dispersion, and by covering the β-FeO(OH) nano-particle with silicon oxide, and thereafter applying heat treatment in an oxidizing atmosphere, and applying centrifugation thereto, and drying and evaporating a supernatant liquid.

7. The magnetic powder according to claim 1 , wherein the crystal structure belongs to a simple lattice (P) of a monoclinic system.

8. A composite magnet comprising the magnetic powder according to claim 1 .

9. A core-shell magnet comprising the magnetic powder according to claim 1 .

Assignees

• Univ Tokyo
• Dowa Electronics Materials Co Ltd

Inventors

• Ohkoshi Shin-Ichi
• YOSHIKIYO Marie
• Namai Asuka
• Tokoro Hiroko
• TARORA Waka
• NASU Tomomichi
• Yoshida Takayuki
• Tanaka Manabu

Classifications

• C01P2006/42

  Magnetic properties · CPC title

• H01F1/11

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C01P2002/90

  Other crystal-structural characteristics not specified above · CPC title

• C01G49/06 Primary

  Ferric oxide [Fe2O3] · CPC title

• C01P2002/77

  by unit-cell parameters, atom positions or structure diagrams · CPC title