Tdk Corporation

Ayato Kakoki

Makoto Iwasaki

Tetsuya Hidaka

Takuma Hayakawa

Takeshi Masuda

Yoshinori Fujikawa

Chikara Ishizaka

Syota Goto

Fumitaka Baba

Haruna Nakajima

Naoto Tsukamoto

An R-T-B based sintered magnet containing a first heavy rare earth element, in which R includes Nd, T includes Co and Fe, the first heavy rare earth element includes Tb or Dy, the R-T-B based sintered magnet has a region in which a concentration of the first heavy rare earth element decreases from the surface toward the inside, a first grain boundary phase which contains the first heavy rare earth element and Nd but does not contain Co is present in one cross section including the region, and an area occupied by the first grain boundary phase in one cross section including the region is 1.8% or less.

R-T-B based sintered magnet

An R-T-B based sintered magnet includes 'R', 'T', and &#x201c;B&#x201d;. &#x201c;R&#x201d; represents a rare earth element. &#x201c;T&#x201d; represents a metal element other than rare earth elements including at least Fe, Cu, Mn, Al, Co, Ga, and Zr. &#x201c;B&#x201d; represents boron or boron and carbon. With respect to 100 mass % of a total mass of the R-T-B based sintered magnet, a content of &#x201c;R&#x201d; is 28.0 to 31.5 mass %, a content of Cu is 0.04 to 0.50 mass %, a content of Mn is 0.02 to 0.10 mass %, a content of Al is 0.15 to 0.30 mass %, a content of Co is 0.50 to 3.0 mass %, a content of Ga is 0.08 to 0.30 mass %, a content of Zr is 0.10 to 0.25 mass %, and a content of &#x201c;B&#x201d; is 0.85 to 1.0 mass %.

An R-T-B based sintered magnet includes 'R', 'T', and &#x201c;B&#x201d;. &#x201c;R&#x201d; represents a rare earth element including at least Tb. &#x201c;T&#x201d; represents a metal element except rare earth elements including at least Fe, Cu, Mn, Al, and Co. &#x201c;B&#x201d; represents boron or boron and carbon. With respect to 100 mass % of a total mass of the R-T-B based sintered magnet, a content of &#x201c;R&#x201d; is 28.0 to 32.0 mass %, a content of Cu is 0.04 to 0.50 mass %, a content of Mn is 0.02 to 0.10 mass %, a content of Al is 0.15 to 0.30 mass %, a content of Co is 0.50 to 3.0 mass %, and a content of &#x201c;B&#x201d; is 0.85 to 1.0 mass %. Tb2/Tb1 is 0.40 to less than 1.0, where Tb1 and Tb2 (mass %) denote a content of Tb at a surface portion and at a core portion, respectively.

Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.

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Tokyo, Japan

Ayato Kakoki