Latent heat of the first-order magnetic transition ofMnFeSi0.33P0.66

Abstract

The latent heat of a magnetoelastic phase transition is used as a measure of the magnetocaloric effect since it is directly proportional to the entropy change. Taking MnFeSi 0.33 P 0.66 as a model magnetocaloric material, density functional theory calculations in addition to the phonon calculations based on the density functional perturbation theory were performed in order to calculate the latent heat of the magnetoelastic phase transition. The Curie temperature (T C ) was determined by taking into account the quasiharmonic approximation and the configurational entropy. The material exhibits a first-order magnetic transition accompanied by a large latent-heat (19.97 kJ/kg) near-room-temperature operation.

Magnetocaloric materials for energy efficient cooling

“…The energy barrier between different magnetic states in the LaFe 13−x Si x alloys is typically below 150 meV/f.u. (Kuz'min and Richter 2007); this value is expected to be even lower in the MnFeSi x P 1−x compounds (Roy et al 2016). These energy barriers are comparable to the thermal energy near 300 K. The effect of the thermal energy is to smear out the transition, therefore, the transition in weak first order materials appears to be smooth (Lyubina et al 2009b, as opposed to the textbook example with a distinct discontinuity in the magnetisation ΔM (see figures 3, 5 and 6).…”

“…Models based on the Bean and Rodbell model that consider the magnetic, crystal lattice and electron contributions to the free energy were developed for the description of the magnetocaloric effect in materials with first order transitions (de Oliveira and von Ranke 2010, Basso 2011). Further models used to describe the magnetocaloric effect include molecular field approximation (Amaral et al 2007), Monte-Carlo method (Nóbrega et al 2006, Buchelnikov et al 2011 and first principles calculation (Paudyal et al 2006, Kuz'min and Richter 2007, Liu and Altounian 2009, Roy et al 2016. It should be noted that first principles calculations can be instrumental in finding materials with properties favourable for magnetic cooling applications (see section 5.3).…”

“…Para-to ferromagnetic transition in the binary Fe 2 P occurs at 217 K; the transition is of first order and occurs without the symmetry change (figure 9, Beckman et al 1982, Yamada andTerao 2002). In MnFeSi x P 1−x , the Fe and Mn atoms preferentially occupy the 3f and 3g positions, respectively, and comprise different alternating layers (Roy et al 2016). The giant MCE in this material family was first reported by Tegus et al (2002) in MnFeP 0.45 As 0.55 .…”

Lattice dynamics across the magnetic transition in(Mn,Fe)1.95(P,Si)

“…Thus, (Mn,Fe) 2 (P,Si) based compounds constitute an ideal playground in order to clarify the nature of magnetoelastic transition. This is not only because the unit cell is rather small, it contains only nine atoms, and the 3d transition metal contribution may be divided into the constituent crystallographic sites, but also because the density of vibrational states is very well structured and the high-energy modes are separated from the low-energy vibrational modes [21].…”