Abstract
The effect of transition metal substitution for Fe and the structural and magnetic properties of Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu, and Zn) compounds were investigated in this study. Rietveld analysis of X-ray data indicates that all the samples crystallize in the hexagonal Th2Ni17 structure. The lattice parameters a, c, and the unit cell volume show TM ionic radii dependence. Both Ga and TM atoms show preferred site occupancy for 12j and 12k sites. The saturation magnetization at room temperature was observed for Co, Ni, and Cu of 69, 73, and 77 emu/g, respectively, while a minimum value was observed for Zn (62 emu/g) doping in Gd2Fe16Ga0.5TM0.5. The highest Curie temperature of 590 K was observed for Cu doping which is 15 and 5% higher than Gd2Fe17 and Gd2Fe16Ga compounds, respectively. The hyperfine parameters viz. hyperfine field and isomer shift show systematic dependence on the TM atomic number. The observed magnetic and Curie temperature behavior in Gd2Fe16Ga0.5TM0.5 is explained on the basis of Fe(3d)-TM(3d) hybridization. The superior Curie temperature and magnetization value of Co-, Ni-, and Cu-doped Gd2Fe16Ga0.5TM0.5 compounds as compared to pure Gd2Fe17 or Gd2Fe16Ga makes Gd2Fe16Ga0.5TM0.5 a potential candidate for high-temperature industrial magnet applications.
Highlights
The rare-earth intermetallic compounds R2Fe17 have energy product (BH)max and Hc to be about 26 MGOe and 15 kOe, respectively [1]
This is evident from the variation in the c/a ratio (Table 1), which indicates the anisotropic expansion of unit cell volume with transition metal (TM) atom doping
The effect of double substitution of Ga and TM in Gd2Fe16Ga0.5TM0.5 on structural and magnetic properties was compared with Gd2Fe17 compounds
Summary
The rare-earth intermetallic compounds R2Fe17 have energy product (BH)max and Hc to be about 26 MGOe and 15 kOe, respectively [1]. Beside these properties, they exhibit low Curie temperature (Tc). Various strategies have been employed addressing issues related to improving magnetic anisotropy, magnetization, and Curie temperature of R2Fe17 compounds. Among Al, Si, and Ga, Ga substituted compounds show high Tc, e.g., for Sm2Fe16Ga, Tc was ~485 K [7]; for Dy2Fe16Ga, Tc was ~462 K [8] This improvement in Tc is overshadowed by a concomitant deterioration in saturation magnetization as iron atoms are being replaced by non-magnetic atoms
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