Structure and magnetic properties ofRNi2Mncompounds(R=Tb,Dy,

The compounds $R{\mathrm{Ni}}_{2}\mathrm{Mn}$ $(R=\mathrm{Tb},\phantom{\rule{0.3em}{0ex}}\mathrm{Dy},\phantom{\rule{0.3em}{0ex}}\mathrm{Ho},\phantom{\rule{0.3em}{0ex}}\mathrm{and}\phantom{\rule{0.3em}{0ex}}\mathrm{Er})$ with a ${\mathrm{MgCu}}_{2}$-type structure have been synthesized. The $R$ to transition metal atom ratio is confirmed to be 1:3 using the energy dispersive spectroscopy. The structural and magnetic properties have been investigated by various experimental methods. The x-ray diffraction patterns (XRD) can be well indexed with a cubic Laves cell and space group Fd3m. The refinement results of the XRD patterns show the presence of vacancies in the crystallographic structure. The ordering temperatures ${T}_{\mathrm{C}}$ have been derived to be 131, 94, 75, and $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $R=\mathrm{Tb},\phantom{\rule{0.3em}{0ex}}\mathrm{Dy},\phantom{\rule{0.3em}{0ex}}\mathrm{Ho}\phantom{\rule{0.3em}{0ex}}\mathrm{and}\phantom{\rule{0.3em}{0ex}}\mathrm{Er}$, respectively, which are much higher than those of their corresponding $R{\mathrm{Ni}}_{2}$ and $R{\mathrm{Mn}}_{2}$ compounds. A large difference of $M\text{\ensuremath{-}}T$ curves between zero-field-cooling and field-cooling magnetization for all samples at a certain temperature range is observed in a low field, which can be understood in the terms of narrow-domain-wall pinning and a sensitive temperature dependence of coercivity.