Suppression of antiferromagnetic interaction by Fe substitutions in NdCo$_2$P$_2$

Abstract

Polycrystalline samples of Nd(Fe$_x$Co$_{1-x}$)$_2$P$_2$ ($0.0 \le x \le 0.3$) with the ThCr$_2$Si$_2$-type structure were synthesized and subsequently characterized by powder X-ray diffraction analysis, magnetization measurements, and $^{57}$Fe Mössbauer spectroscopy. The powder X-ray diffraction results show that the lattice parameters change monotonically with increasing Fe content x; i.e., the value of a decreases and that of c increases. The Néel temperature $T_\textrm{N}=251~\mathrm K$ observed for $x=0$ decreases to 182 K for $x=0.05$ and 147 K for $x=0.1$, which means the antiferromagnetic order in Co was suppressed by the substitution of Fe. The $^{57}$Fe Mössbauer spectra of the prepared compounds could be reproduced using a single Lorentzian function. Assuming that the broadening observed at low temperatures is due to magnetic interactions, the magnitude of the hyperfine field was estimated to be approximately 1.6 T. This magnitude of the hyperfine field suggests that the magnetic moment of Fe is approximately 0.1 $\mu _\textrm{B}$.