TY - JOUR
T1 - Phase relations and extrinsic magnetic properties of Sm–(Fe,Co)–Ti–(Ga)-based alloys for ThMn12-type permanent magnets
AU - Srinithi, A. K.
AU - Sepehri-Amin, H.
AU - Tang, Xin
AU - Tozman, P.
AU - Li, J.
AU - Zhang, J.
AU - Kobayashi, S.
AU - Ohkubo, T.
AU - Nakamura, T.
AU - Hono, K.
N1 - Funding Information:
This work was performed with the approval of the SPring-8 Program Advisory Committee (Proposal No. 2019A1007). This work was supported in part by ESICMM, Grant Number JPMXP0112101004, through the Ministry of Education, Culture, Sports, Science and Technology (MEXT). P. T. acknowledges NIMS for the provision of the ICYS fellowship.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/7/1
Y1 - 2021/7/1
N2 - Realizing a non-ferromagnetic intergranular phase for the ThMn12-type Sm(Fe,Co,Ti)12 compound is a prerequisite for developing high coercive magnets. In this work, we demonstrate that the addition of Ga into the Sm-(Fe,Co)-Ti system results in the formation of non-ferromagnetic Sm–Ga-rich intergranular phases with good wettability on Sm(Fe,Co,Ti)12 grains. In the Sm-(Fe,Co)-Ti system, when the alloy composition was varied to the Sm-rich region as Sm1+w(Fe0.8Co0.2)11Ti (w = 0–0.7), soft ferromagnetic C15-type Sm(Fe,Co)2 intergranular phase and TbCu7-type Sm(Fe,Co,Ti)~7 phase formed along with the ThMn12-type main phase in the as-cast alloy. We demonstrated that by introducing Ga, the formation of these secondary soft ferromagnetic phases can be hindered as the excess Sm and Ga formed non-ferromagnetic Ba5Si3-type Sm5Ga3 and TII-type SmGa intergranular phases with an excellent wettability on Sm(Fe,Co,Ti)12 grains. Fine Sm(Fe,Co,Ti)12 grains of 1–2 µm, well isolated by the Sm–Ga-rich intergranular phase, were realized by melt-spinning the Ga-doped alloy and the maximum coercivity obtained was 0.5 T. According to the detailed microstructure characterizations, the weak-links to the coercivity of this novel microstructure of well-isolated and fine Sm(Fe,Co,Ti)12-based grains is the presence of defects at the interfaces which could lead to a locally reduced magneto-crystalline anisotropy.
AB - Realizing a non-ferromagnetic intergranular phase for the ThMn12-type Sm(Fe,Co,Ti)12 compound is a prerequisite for developing high coercive magnets. In this work, we demonstrate that the addition of Ga into the Sm-(Fe,Co)-Ti system results in the formation of non-ferromagnetic Sm–Ga-rich intergranular phases with good wettability on Sm(Fe,Co,Ti)12 grains. In the Sm-(Fe,Co)-Ti system, when the alloy composition was varied to the Sm-rich region as Sm1+w(Fe0.8Co0.2)11Ti (w = 0–0.7), soft ferromagnetic C15-type Sm(Fe,Co)2 intergranular phase and TbCu7-type Sm(Fe,Co,Ti)~7 phase formed along with the ThMn12-type main phase in the as-cast alloy. We demonstrated that by introducing Ga, the formation of these secondary soft ferromagnetic phases can be hindered as the excess Sm and Ga formed non-ferromagnetic Ba5Si3-type Sm5Ga3 and TII-type SmGa intergranular phases with an excellent wettability on Sm(Fe,Co,Ti)12 grains. Fine Sm(Fe,Co,Ti)12 grains of 1–2 µm, well isolated by the Sm–Ga-rich intergranular phase, were realized by melt-spinning the Ga-doped alloy and the maximum coercivity obtained was 0.5 T. According to the detailed microstructure characterizations, the weak-links to the coercivity of this novel microstructure of well-isolated and fine Sm(Fe,Co,Ti)12-based grains is the presence of defects at the interfaces which could lead to a locally reduced magneto-crystalline anisotropy.
KW - Coercivity
KW - Microstructure
KW - Permanent magnets
KW - Phase relations
KW - ThMn type structure
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U2 - 10.1016/j.jmmm.2021.167866
DO - 10.1016/j.jmmm.2021.167866
M3 - Article
AN - SCOPUS:85102363462
SN - 0304-8853
VL - 529
JO - Journal of Magnetism and Magnetic Materials
JF - Journal of Magnetism and Magnetic Materials
M1 - 167866
ER -