Magnetic Properties and Large Magnetocaloric Effect in Amorphous Fe-Ag-Ni-Zr for Room-Temperature Magnetic Refrigeration

摘要

This paper reveals that a partial replacement of Fe by Ni (5%) and/or Ag (2%) in amorphous FeAgNiZr( and 2) alloys leads to the shift of toward room temperature (RT) ( and 303 K for and 2, respectively). Basing on isothermal magnetization data, the magnetic entropy change ( of the amorphous alloys was calculated. Their maximum values () achieve just around RT, corresponding to the ferromagnetic-paramagnetic (FM-PM) phase transition of the amorphous phase. Under a magnetic field change of 10 kOe, values are J . We have also used different methods, such as the modified Arrott plots, the Kouvel–Fisher method, and critical isotherm analysis to study their critical property around the FM–PM phase transition. Our results suggest th- t the amorphous FeAgNiZr alloys exhibit a second-order magnetic phase transition with the critical exponents of –0.396 and –1.334 close to those expected for the 3-D Heisenberg model. This proves the existence of short-range FM interactions in these alloys.