Latent heat of magnetization of MnFeSiP-system

Abstract

Magnetic refrigeration became one of the most popular fields of research among the magnetic materials. After the discovery of the Giant magnetocaloric effect (GMCE) in Gd₅Si₂Ge₂, many new materials (viz. LaFeSi₁₃, Heusler alloys, FeRh etc.) have been proposed in the past decade. Mn_x-Fe_1-xSi_yP_1-y series of materials are among the best performing materials, in terms of efficiency, availability, cost, environmental friendliness etc [1]. MnFeSiP materials show a simultaneous transiton of the magnetic state accompanied by an elastic transition, which is considered to be the reason behind its high magnetocaloric efficiency. Recently the underlying mechanism of this 'magneto-elastic' transition was explained by employing density functional theory. The coexistance of strongly and weakly magnetic atoms give rise to the effect called 'mixed magnetism'. [2] The efficiency of these materials are determined by the adiabatic temperature change and magnetic entropy change at the Curie temperature. These two quantities are directly proportional to the latent heat of magnetization (L). So the determination of L is essential for determining the usefulness of such system. Experimentally L can be determined using differential scanning calorimetry. Determination of the latent heat can also be done using ab-initio calculation, which is useful in characterizing such systems based on their efficiency. The accurate values of the free energy above and below the transition temperature are needed to obtain the magnetic latent heat and the transition temperature.