Enhanced magnetocaloric properties and critical behavior of (Fe_0.72Cr_0.28)₃Al alloys for near room temperature cooling

Magnetic cooling is an environmentally friendly, energy efficient, thermal management technology relying on high performance magnetocaloric materials (MCM). Current research has focused on low cost, corrosion resistant, rare earth (RE) free MCMs. We report the structural and magnetocaloric properties of novel, low cost, RE free, iron based (Fe_0.72Cr_0.28)₃Al alloys. The arc melted buttons and melt spun ribbons possessed the L2₁ crystal structure and B2 crystal structure, respectively. A notable enhancement of 33% in isothermal entropy change (−Δ S _m) and 25% increase in relative cooling power (RCP) for the ribbons compared to the buttons can be attributed to higher structural disorder in the Fe–Cr and Fe–Al sub-lattices of the B2 structure. The critical behavior was investigated using modified Arrott plots, the Kouvel–Fisher plot and the critical isotherm technique; the critical exponents were found to correspond to the short-range order 3D Heisenberg model. The field and temperature dependent magnetization curves of (Fe_0.72Cr_0.28)₃Al alloys revealed their soft magnetic nature with negligible hysteresis. Thus, these alloys possess promising performance attributes for near room temperature magnetic cooling applications. (paper)