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

Abstract

Monte Carlo modeling suggests that the magnetothermal features of the Fe2P-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 ΔSm(T) presents a plateau-like behavior which can be tailored by tuning either the JCr-Fe/JCr-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 (Tac) a canted antiferromagnetic phase and at the upper bound (Tdc) the thermally disordered phase. The refrigerant capacity and adiabatic change of temperature are A(H)(Tdc - Tac) and A(H)Tp/Cm respectively, with Tac < Tp < Tdc, A(H) an increasing positive function of the field defining the height of the plateau and Cm the magnetic specific heat, whose critical behavior is related to the T(a,d)(c) values.

Ab Initio Studies on Structural, Elastic, Thermodynamic and Electronic Properties of FeCrAs under Pressures

“…FeCrAs displaying under pressure and temperature, previous eort have been paid the emphasis on the optical, magnetism, and conductive properties of this compound [2,5,6]. Wu et al [1] reported that when the * corresponding author; e-mail: dechunhe@126.com temperature is below 10 K, the resistivity follows a nonFermi-liquid power law while the specic heat shows Fermi-liquid behavior with a large Sommerfeld cocient.…”

Geometrically frustrated Fe2P-like systems: beyond the Fe-trimer approximation

“…On the other hand, exchange couplings J 3f-3f and J 3f-3g are considered antiferromagnetic [5,6], which gives rise to a strong frustration not just due to the triangular nature of the layers but to the sandwiched coupling of the triangles between the 3f layers at the center of which the trimers are located. The magnetothermal observables (MO) are calculated and analyzed with respect to all these parameters.…”

“…Geometrically frustrated magnets are among the most exciting systems in materials science and condensed matter as they can potentially exhibit many exotic phenomena, e.g., spin liquids [1,2], skyrmions [3], modulated ferroelectrics [4] and recently new magnetocaloric effects [5]. There are several types of frustrated magnets, with the Kagome-like (or hexagonal) lattices perhaps the most studied layered systems.…”

“…In this work we focus on a particular strongly frustrated material structure, i.e., Fe 2 P, which is formed from the aforementioned lattices by stacking them upon each other, with isolated triangles of Fe centered at the distorted-Kagome hexagonal sites. We refer readers to previous theoretical and experimental works [5,6] which include a full description of the crystal structure. For our purpose Figure (1) is sufficient to exemplify the spin architecture.…”

“…al. [5]. This last investigation used the so-called trimer approximation which simplifies the 3g-trimers by replacing them with an effective spin site.…”