Advance of Magnetocaloric Effect and Materials

Dear Colleagues,

The aim of this Special Issue is to give the opportunity to researchers working in fields related to the advancement of magnetocaloric effects and materials to submit review papers, full articles, and short communications.

In last recent years, magnetic refrigeration at room temperature has seen renewed interest thanks to the development of new materials with enhanced magnetocaloric effects and new thermal engineering techniques. High potential efficiency and environmental compatibility make magnetic refrigeration competitive as an alternative to conventional technologies based on the compression–evaporation cycle. New magnetocaloric materials for solid-state caloric refrigeration are emerging, and their various applications demonstrate that they are essential in our everyday lives. Thus, these magnetocaloric materials play important roles in addressing today's challenges, particularly those concerning fossil fuel consumption and climate change.

This Issue represents the state of the art in the field of new magnetocaloric materials and new cooling techniques. The aim is to highlight the latest developments in the shaping of magnetocaloric materials. Researchers are therefore invited to present all their original scientific and technical articles of experimental and theoretical studies on a wide range of materials and processes. Topics should include magnetocaloric materials, systems and applications in heating, cooling, and energy conversion.

Prof. Dr. Lotfi Bessais
Guest Editor

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• magnetocaloric effect
• theoretical prediction
• magnetocaloric materials
• magnetic refrigeration
• energy conversion
• heat pumps

Title: Band structure calculations, magnetic properties and magnetocaloric effect of GdCo1.8M0.2 compounds with M=Fe, Mn, Cu, Al
Authors: Gabriela Souca 1; Roxana Dudric1,; Karsten Küpper2; Coriolan Tiusan1,3; Romulus Tetean1
Affiliation: 1Faculty of Physics, Babes-Bolyai University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania 2University of Osnabrück, Fachbereich Physik, 49069 Osnabrück, Germany 3National Center of Scientific Research, France
Abstract: The band structure, magnetic properties and magnetocaloric effect of GdCo1.8M0.2 with M=Fe, Mn, Cu and Al were investigated. The samples were prepared by induction melting technique and all of them are single phase with the cubic MgCu2 - Laves type structure as reveal by X-ray diffraction measurements. The band structure calculations demonstrate that all the samples have a ferrimagnetically ordered ground state, in perfect agreement with the magnetic measurements. A larger theoretically issued Gd moments with respect to the atomic expectation is explained by a mechanism involving the hybridization of the Gd-5d and Co-3d orbitals. The XPS measurements reveal no significant shift in the binding energy of the investigated Co core levels with the change of the dopant element, as expected considering that the lattice parameter and hence the distance between the atoms have close values. For all investigated samples, the Co 3s core level spectra give us direct evidence of the local magnetic moments on Co sites and an average magnetic moment atom can be estimated being, the values obtained being in very good agreement with the values obtained from band structure calculations and magnetic measurements. From the Mn 3s core level spectra an approximate value of the manganese magnetic moment was obtained. The symmetric shapes of magnetic entropy changes have shown the presence of a second order magnetic phase transition. These was confirmed by the absence of inflexion points around transition temperatures in the Arrott plots and the temperature dependence of Landau coefficients. The calculated relative cooling power, RCP(S), normalized relative cooling power at the applied magnetic field, RCP(∆S)/∆B, and temperature-averaged entropy change, TEC parameters show that these compounds could be promising candidates for applications in magnetic refrigeration devices.