Magnetic phase transition and Mossbauer spectroscopy of ErNi2Mnx compounds

Abstract

Investigation of ErNi(2)Mn(x) with 0.90 <= x <= 1.10 indicates that the MgCu(2)-type structure (with space group Fd-3m) is formed within x = 0.97-1.10. Curie temperature T(C) = 50 K of ErNi(2)Mn is significantly higher than those of the corresponding ErNi(2) (T(C) = 7 K) and ErMn(2) (T(C) = 15 K) compounds. Detailed analyses of DC magnetization data demonstrate that the magnetic phase transition at the Curie temperature is second order. The magnetic entropy change around T(C) has been found to be 4.8 J/kg K for a magnetic field change of 0 to 5 T with its relative cooling power similar to 283 J/kg. (57)Fe Mossbauer spectra below T(C) have been fitted with three sub-spectra representing three inequivalent local magnetic environments while the paramagnetic spectra are fitted using two sub-spectra for two inequivalent crystal sites (8a and 16d), which supports the conclusion based on Rietveld refinement that Mn atoms occupy at both 8a and 16d sites. (C) 2011 American Institute of Physics.