Magnetic entropy change plateau in a geometrically frustrated layered system: FeCrAs-like iron-pnictide structure as a magnetocaloric prototype

摘要

Monte Carlo modeling suggests that the magnetothermal features of the Fe_2P-structured FeCrAs-like compound offer a promising route for the design of magnetocaloric materials. The prototype structure is modeled as antiferromagnetically coupled layered Heisenberg systems mimicking the distorted Kagome/triangular stacked architecture of FeCrAs iron-pnictide. The magnetic entropy change ΔS_m (T) presents a plateau-like behavior which can be tailored by tuning either the J_(Cr-Fe)/J_(Cr-Cr) exchange energy ratio or the magnetic field. The plateau is defined by cooperative spin ordering within a ferrimagnetic region which exists between two critical temperatures separating at the lower bound (T_c ~a) a canted antiferromagnetic phase and at the upper bound (T_c ~d) the thermally disordered phase. The refrigerant capacity and adiabatic change of temperature are and A(H) T_c ~d-T _c ~aT_(p/C)m respectively, with T_c ~a