Magnetocaloric effect and critical behavior of the Mn-rich itinerant material Mn₃GaC with enhanced ferromagnetic interaction*

Abstract

We revisit the reversible magnetocaloric effect of itinerant ferromagnet Mn3GaC near the ferromagnetic to paramagnetic phase transition by adopting the experimental and theoretical methods and critical behavior of Mn-rich Mn3GaC with an enhanced FM interaction. Landau theory model cannot account for temperature dependent magnetic entropy change which is estimated from thermal magnetic methods only considering magnetoelastic coupling and the electron–electron interaction, apart from molecular mean-field model. Critical behavior is studied by adopting the modified Arrott plot, Kouvel–Fisher plot, and critical isotherm analysis. With these critical exponents, experimental data below and above T c collapse into two universal branches, fulfilling the single scaling equation m = f ±(h), where m and h are renormalized magnetization and field. Critical exponents are confirmed by Widom scaling law and just between mean-field model and three-dimensional Heisenberg model, as the evidence for the existence of long-range ferromagnetic interaction. With increasing the Mn content, T c increases monotonously and critical exponents increases accordingly. The exchange distance changes from J(r) ∼ r –4.68 for x = 0 to J(r) ∼ r –4.71 for x = 0.08, respectively, which suggests the competition of the Mn–Mn direct interaction and the itinerant Mn–C–Mn hybridization. The possible mechanism is proposed.

Competing Magnetic Interactions, Structure and Magnetocaloric Effect in Mn3sn1-Xznxc Antiperovskite Carbides

“…The experimental value of the Mn-Mn distance is determined for alloys, in which magnetic order is considered in terms of direct exchange interactions. Previous studies suggested the presence of different mechanisms in antiperovskites, such as the Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions [38,39]. Unlike the previously mentioned Mn-based compounds, Mn 4 N crystallizes in the antiperovskite type of structure and shows a ferrimagnetic behaviour, which can lead to a better match of the experimentally estimated critical distance between Mn atoms.…”

Structure, magnetism and magnetocaloric effects in Er5Si3B x (x = 0.3,0.6) compounds

“…[1][2][3][4][5][6][7] The novel solid-state refrigeration technology based on the magnetocaloric effect (MCE) is one of the most promising replacements for conventional refrigeration technologies because of its high efficiency and non-emission of pollutants. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] The MCE is the thermodynamic response of the magnetic material to an applied magnetic field, meaning that the magnetic moment transforms from ordered to disordered (or ordered to ordered) during the imposition of an applied magnetic field, resulting in a change in magnetic entropy. [24] The maximum magnetic entropy changes (−∆S max M ) generally appear near the magnetic phase transition temperature, so the magnetic phase transition is strongly correlated with the MCE.…”