Effects of the doping element on crystal structure and magnetic properties of Sm(Co,M)7 compounds (M=Si, Cu, Ti, Zr, and Hf)

Effects of Hf and CNTs on structure and magnetic properties of TbCu7-type Sm–Co magnets

“…So they are hard to be identified as an accurate phase. Anyway, it can be learned that Hf can stabilize 1:7H structure and restrict the formation of 1:5 and 2:17 phases, which is consistent with the results reported by Guo and his coworkers [4][5][6]. On the other hand, it indicates that the chemical affinity between Hf and Co is higher than that between Hf and Sm, so no Sm-Hf new phases are formed.…”

“…The electronegativities of C, Co, Sm and Hf are 2.50, 1.70, 1.07 and 1.23, respectively [6]. The elements with larger electronegativity difference prefer to combine together, thus the affinities to form ionic bond, from big to small, are Sm-C(1.43), Hf-C(1.27), HfCo(0.47) and Hf-Sm(0.16).…”

“…Because the electronegativity of Hf is lower than that of Co, Hf tends to occupy 2e sites preferentially and substitute for some of Co atoms [4]. Generally, Hf can be visualized as nonmagnetic element, so the saturation magnetization should decrease with increasing content of the doping element [6]. What is hard to explain is that the moment of SmCo 6.9 Hf 0.1 during magnetization is higher than that of pure SmCo 7 all along.…”

“…However, pure SmCo 7 phase can not steadily exist, so a third element such as Si, Cu, Ga, Nb or Hf, is necessary to stabilize the TbCu 7 -type Sm-Co 1:7 phase and to improve its magnetic properties. Guo and his coworkers [3][4][5][6][7] directly prepared some Sm-Co 1:7 intermetallic compounds by arc melting. Among those third elements M, Hf has been reported the most powerful both in stabilizing the TbCu 7 -type structure and in enhancing its magnetocrystalline anisotropy field, meanwhile, it possesses high magnetization.…”

Influence Of Cooling Rate On Phase Composition And Magnetic Properties Of Sm12.5Co66.5Fe8Cu11Si2 Alloy In The Form Of Ribbon In As-Quenched State

“…If the electronegativity of added component(s) M is smaller than for Co, atoms of alloying additives prefer certain locations in the lattice (2e instead of 3g). However, if the amount of M is too great (x >3) its atoms will prefer location 2c, [11,12]. If alloying additive atoms take locations 2e and 3g in the SmCo 7 lattice, there is an increase in magnetocrystalline anisotropy and an improvement in magnetic properties, whereas atoms taking location 2c cause a decrease in magnetocrystalline anisotropy and a worsening of magnetic properties.…”