Ferrite sintered magnet

Patent metadata

Field	Value
Publication number	US-2021296032-A1
Application number	US-202117207085-A
Country	US
Kind code	A1
Filing date	Mar 19, 2021
Priority date	Mar 23, 2020
Publication date	Sep 23, 2021
Grant date	—

Abstract

A ferrite sintered magnet including ferrite grains having a hexagonal crystal structure. The ferrite grains satisfy 0.56≤W≤0.68 where W is an average value of circularities of the ferrite grains in a cross section parallel to an axis of easy magnetization.

First claim

What is claimed is:

1 . A ferrite sintered magnet comprising ferrite grains having a hexagonal crystal structure, wherein
the ferrite grains satisfy 0.56≤W≤0.68 where W is an average value of circularities of the ferrite grains in a cross section parallel to an axis of easy magnetization.

2 . The ferrite sintered magnet according to claim 1 , wherein
an average value of Heywood diameters of the ferrite grains in the cross section is 1.00 μm or more and 1.23 μm or less.

3 . The ferrite sintered magnet according to claim 1 comprising 0.010 mass % or more and 0.090 mass % or less of Mg in terms of MgO.

4 . The ferrite sintered magnet according to claim 1 comprising Ca, R, A, Fe and Co in an atomic ratio of Ca 1-w-x R w A x Fe z Co m , wherein
R includes La only or includes La and at least one selected from rare earth elements,
A is at least one selected from Ba and Sr,
0.364≤w≤0.495,
0.038≤x≤0.136,
8.280≤z≤10.45 and
0.257≤m≤0.338.

5 . The ferrite sintered magnet according to claim 1 , comprising Ca, R, A, Fe and Co, wherein
R includes La only or includes La and at least one selected from rare earth elements, A is at least one selected from Ba and Sr, Ca is 2.505 mass % or more and 2.951 mass % or less in terms of CaO, R is 8.028 mass % or more and 8.239 mass % or less in terms of R 2 O 3 , A is 0.666 mass % or more and 1.666 mass % or less in terms of AO, Fe is 84.564 mass % or more and 84.937 mass % or less in terms of Fe 2 O 3 , and Co is 2.341 mass % or more and 2.521 mass % or less in terms of CoO.

6 . The ferrite sintered magnet according to claim 1 , comprising 0.005 mass % or more and 0.058 mass % or less of B in terms of B 2 O 3 .

Assignees

• Tdk Corp

Inventors

• Ikeda Masanori
• Morita Hiroyuki
• Murakawa Yoshitaka
• Muroya Shogo

Classifications

• H01F1/11 Primary

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

• H01F1/10

  non-metallic substances, e.g. ferrites {, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure} · CPC title

• C04B2235/788

  Aspect ratio of the grains · CPC title

• C04B2235/786

  Micrometer sized grains, i.e. from 1 to 100 micron · CPC title

• C04B2235/767

  Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites · CPC title