Comparison of magnetocaloric properties of the Mn2−xFexP0.5As0.5 (x = 1.0 and 0.7) compounds

Abstract

The Mn2−xFexP0.5As0.5 compounds (x = 0.7 and 1.0) studied exhibit the magnetic phase transitions, which are accompanied by a magnetic entropy change. For x = 1 the PM–FM transition is of the first order one with a weak (2–3 K) thermal hysteresis in the vicinity of TC = 275 K. The Mn1.3Fe0.7P0.5As0.5 compound possesses two magnetic transitions: the second-order PM–FM transition at TC = 190 K, followed by the FM–AFM transition at TN = 90 K, leading to normal and inverse magnetocaloric effects, respectively. The maximum values of magnetic entropy change are equal to 17 J kg−1 K−1 in MnFeP0.5As0.5 and 5 J kg−1 K−1 in Mn1.3Fe0.7P0.5As0.5 for a field change of 5 T. The magnetic entropy changes were calculated using both the isofield magnetization curves versus temperature and the isothermal magnetization curves versus applied magnetic field. The magnetocaloric effect in MnFeAs0.5P0.5 is discussed in the terms of both the thermodynamic Maxwell relation and the Clausius–Clapeyron equation.