Magnetic and magnetocaloric properties of the Mn2-xFexP0.5As0.5 (0 ≤ x ≤ 0.5) system alloys

Abstract

The experimental data on magnetic and magnetocaloric properties of the Mn_2–xFe_xP_0.5As_0.5 (0 ≤ x ≤ 0.5)-system alloys are presented. The magnetization measurements are made in the 4.2–700 K temperature range in magnetic fields up to 8 T. The magnetization isotherms taken near the temperatures of spontaneous occurrence of the ferromagnetic phase (Т_C,Т_АF–FМ1) are used to determine changes in entropy ΔS with magnetic field varying from 0 to 2, 4, 5, 8 T, and to construct the ΔS(T) dependences. It is found that Т_C and Т_АF–FМ1 decrease monotonously with increasing the manganese concentration and the ferromagnetic phase in Мn_1.5Fe_0.5P_0.5As_0.5 are completely suppressed. It is shown that the concentration dependences of maximum entropy jump (and of corresponding refrigeration capacity) and ferromagnetic moment of the unit cell are extreme with maxima at x = 0.9 and 0.8, respectively. The obtained data are compared with the values of ferromagnetic moments calculated from the first principles by the Korringa–Kohn–Rostoker and coherent potential approximation (KKR–CPA) method — the discrepancy at 0.5 ≤ x ≤ 0.7 is supposed to be due to the occurrence of antiferromagnetic components of the magnetic structure. In conclusion it may be said that Mn_2-xFe_xP_0.5As_0.5 alloys are promising in magnetic refrigerator applications at room-temperature.