# US 2021/0280345 A1 · Magnet structure

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- Number: US 2021/0280345 A1
- Document ID: US20210280345A1
- Status: Published application
- Kind: A1
- Application number: 17/186,770
- Filed: 2021-02-26
- Published: 2021-09-09
- Earliest claimed: 2020-03-03
- Assignees: TDK Corporation
- Applicants: TDK Corporation
- Inventors: Taeko TSUBOKURA; Toshihiro KUROSHIMA; Koji MITAKE; Takeshi MASUDA
- Web page: https://patentgrep.com/patent/US20210280345A1

## CPC

- H01F 1/0577: {sintered}
- H01F 41/0293: {diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

A magnet structure includes a first sintered magnet, a second sintered magnet, and an intermediate layer disposed between the first sintered magnet and the second sintered magnet. Each of the first sintered magnet and the second sintered magnet independently includes crystal grains containing a rare earth element, a transition metal element, and boron. The intermediate layer contains rare earth element oxide phases and crystal grains containing a rare earth element, transition metal element, and boron. Each of the transition metal elements independently includes Fe or a combination of Fe and Co. An average coverage factor of the rare earth element oxide phases measured on the basis of a cross section perpendicular to the intermediate layer of the magnet structure is within a range of 10% to 69%.

## Claims

### Claim 1

A magnet structure comprising:
a first sintered magnet;
a second sintered magnet; and
an intermediate layer disposed between the first sintered magnet and the second sintered magnet,
wherein each of the first sintered magnet and the second sintered magnet independently includes crystal grains containing a rare earth element, a transition metal element, and boron,
the intermediate layer contains rare earth element oxide phases and crystal grains containing a rare earth element, a transition metal element, and boron,
each of the transition metal elements independently includes Fe or a combination of Fe and Co, and
an average coverage factor of the rare earth element oxide phases measured on the basis of a cross section perpendicular to the intermediate layer of the magnet structure is within a range of 10% to 69%.

### Claim 2 (depends on 1)

The magnet structure according to claim 1,
wherein an average thickness of the rare earth element oxide phases is within a range of 3 to 30 μm.

### Claim 3 (depends on 1)

The magnet structure according to claim 1,
wherein a c axis of the first sintered magnet and a c axis of the second sintered magnet are non-parallel to each other.

### Claim 4 (depends on 1)

The magnet structure according to claim 1,
wherein a composition of the first sintered magnet and a composition of the second sintered magnet differ from each other.

### Claim 5 (depends on 1)

The magnet structure according to claim 1,
wherein the average coverage factor is within a range of 36% to 68%.

### Claim 6 (depends on 1)

The magnet structure according to claim 1,
wherein concentration of total rare earth elements in the rare earth element oxide phases are within a range of 50 to 85 mass %.

### Claim 7 (depends on 1)

The magnet structure according to claim 1,
wherein the rare earth element in the rare earth element oxide phases are at least one selected from the group consisting of Nd, Pr, Dy, Tb, Ho, and Gd.