Permanent magnets and R-TM-B based permanent magnets
View Patent ↗Permanent magnets in which the ferromagnetic phase is matched with the grain boundary phase, and permanent magnets in which magnetocrystalline anisotropy in the vicinity of the outermost shell of the major phase is equivalent in intensity to that in the inside to suppress nucleation of the reverse magnetic domain, more specifically having a magnetocrystalline anisotropy not less than one-half the magnetocrystalline anisotropy of the interiors of the ferromagnetic grains, are disclosed.
1. A rare-earth magnetic powder having an intrinsic coercivity iHc of at least 17.7 kOe for use in bonded magnets, comprising a R 2 TM 14 B phase and at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba present in an interface of said R 2 TM 14 B phase, wherein R is a rare earth element or Y, and TM is a transition metal in a matched state relative to the R 2 TM 14 B phase.
2. The rare-earth magnetic powder for bonded magnets as defined in claim 1 , wherein said alkaline earth metal has a lattice constant a in a range of 4.7 to 5.7 Å.
3. The rare-earth magnetic powder for bonded magnets as defined in claim 1 , wherein
the crystallographic orientation in the vicinity of an interface between the magnetic phase and a grain boundary phase diffused with said alkaline earth metal is represented by at least one set of the following expressions (A) to (E):
(001)major phase//(110)grain boundary phase and [110]major phase//[001]grain boundary phase (A)
(001)major phase//(221)grain boundary phase and [110]major phase//[111{overscore ( )}]grain boundary phase (B)
(001)major phase//(111)grain boundary phase and [100]major phase//[11{overscore ( )}0]grain boundary phase (C)
(001)major phase//(201)grain boundary phase and [110]major phase//[010]grain boundary phase (D)
(001)major phase//(22{overscore (3)})grain boundary phase and [110]major phase//[110]grain boundary phase (E).
4. The rare-earth magnetic powder for bonded magnets as defined in claim 1 , wherein the alkaline earth metal is present in an amount of 0.5 to 5 parts by weight of alkaline earth metal per 100 parts by weight of R 2 TM 14 B.
5. A rare-earth magnetic powder having an intrinsic coercivity iHc of at least 17.7 kOe for use in bonded magnets, the rare-earth magnetic powder comprising polycrystalline grains of R 2+x TM 14 B and at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba diffused in a grain boundary of the polycrystalline grains of R 2+x TM 14 B so as to match with the R 2+x TM 14 B grains, wherein R is a rare earth element or Y, TM is a transition metal, and 0≦x≦0.3.