Over the last two decades, the research activities on magnetocalorics have been exponentially increased, leading to the discovery of a wide category of materials including intermetallics and oxides. Even though the reported materials were found to show excellent magnetocaloric properties on a laboratory scale, only a restricted family among them could be upscaled toward industrial levels and implemented as refrigerants in magnetic cooling devices. On the other hand, in the most of the reported reviews, the magnetocaloric materials are usually discussed in terms of their adiabatic temperature and entropy changes (ΔTad and ΔS), which is not enough to get more insight about their large scale applicability. In this review, not only the fundamental properties of the recently reported magnetocaloric materials but also their thermodynamic performance in functional devices are discussed. The reviewed families particularly include Gd1-xRx alloys, LaFe13-xSix, MnFeP1-xAsx, and R1-xAxMnO3 (R = lanthanide and A = div...

Advanced materials for magnetic cooling: Fundamentals and practical aspects

We report the theoretical investigations on the giant magnetocaloric compound ${\mathrm{MnFeP}}_{0.45}{\mathrm{As}}_{0.55}$. The magnetic state equation used takes into account the magnetoelastic effect that leads the magnetic system to order under first order paramagnetic-ferromagnetic phase transition. The model parameters were determined from the magnetization data adjustment and used to calculate the magnetocaloric thermodynamic quantities. The theoretical calculations are compared with the available experimental data.

Calculation of the giant magnetocaloric effect in the MnFeP 0.45 As 0.55 compound

Magnetic and magnetocaloric properties of single crystal double perovskite La2MnNiO6 have been investigated in details. Its ordered phase with a high Curie temperature (TC = 280 K) exhibits a significant refrigerant capacity around room temperature. A model based on the mean field theory approximation has been used in order to quantify the magnetic and magnetocaloric properties in the ordered La2MnNiO6. The magnetization and entropy changes were satisfactorily simulated as a function of temperature and magnetic field. On the other hand, the presence of cationic disorder in La2MnNiO6 phases allows to shift the Curie point to low temperature without a significant change in the magnetocaloric performance.

A study of the phase transition and magnetocaloric effect in multiferroic La2MnNiO6 single crystals

The magnetic phase transitions in the $\mathrm{Fe}\mathrm{Mn}{\mathrm{P}}_{1\ensuremath{-}x}{\mathrm{As}}_{x}$ compounds with $x=$ 0.25, 0.35, 0.45, 0.50, and 0.55, have been studied by iron-57 M\"ossbauer spectroscopy. The ferromagnetic and antiferromagnetic spectra have been analyzed with a model that takes into account the random distribution of the P and As near-neighbor anions of a given iron site. This distribution is a binomial distribution of the contributions to the spectra of each iron with $n$ As near neighbors. A magnetostriction model has been used to characterize the temperature induced paramagnetic to ferromagnetic first-order phase transition and order parameters, ${\ensuremath{\eta}}_{\mathrm{F}}=2.6$, 2.3, 2.0, 1.57, and 1.43 have been obtained for $x=0.25$, 0.35, 0.45, 0.50, and 0.55, respectively. A detailed phase diagram has been derived from the M\"ossbauer spectral analysis and reveals a magnetic triple point at $x=\ensuremath{\sim}0.35$ and $\ensuremath{\sim}210\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A model that takes into account the random binomial P and As distribution and the contribution from the iron and manganese magnetic sublattices yields excellent fits of the spectral components assigned to the ferromagnetic and incommensurate antiferromagnetic components for the $x=0.25$ and 0.35 compounds at all temperatures.

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Mössbauer spectral study of the magnetocaloric FeMnP1-xAsx compounds

Neutron diffraction study of history dependence in MnFeP0.6Si0.4

On the basis of the relation T(σ,H) derived within the framework of the Bean–Rodbell model a semiquantitative analysis of (B,T) magnetic phase diagrams in the hexagonal region of the MnFeP1−xAsx (0.15⩽x⩽0.66) series of compounds was carried out. It was found that the first order transition line in the (B,T) plane is terminated by the isolated critical point for x=0.33 and x=0.5 contents. The positive value of dBC/dT and the saturation of the magnetization was found to be in agreement with the experiment. Thus the Bean–Rodbell model and the molecular field approximation can be applied to describe the discontinuous Ferro–Para magnetoelastic phase transition. Semiquantitative agreement between the theoretical and the experimental (B,T) magnetic phase diagrams was obtained. For the MnFeP0.67As0.33 compound the electronic structure calculations were performed by the Korringa–Kohn–Rostoker with the coherent potential approximation method. The density of states (DOS) curve calculated in the nonmagnetic state sho...

M. Guillot

Papers

Semiquantitative analysis of magnetic phase transitions in the MnFeP1−xAsx series of compounds

Semiquantitative Analysis of Magnetic Phase Transition in MnFep/sub 1-x/As/sup x/ Series of Compounds