Advanced materials for magnetic cooling: Fundamentals and practical aspects

Abstract

International audienceOver 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=divalent alkaline earth)–based compounds. Other relevant practical aspects such as mechanical stability, synthesis, and corrosion issues are discussed. In addition, the intrinsic and extrinsic parameters that play a crucial role in the control of magnetic and magnetocaloric properties are regarded. In order to reproduce the needed magnetocaloric parameters, some practical models are proposed. Finally, the concepts of the rotating magnetocaloric effect and multilayered magnetocalorics are introduced

Analysis of the Anisotropic Magnetocaloric Effect in RMn2O5 Single Crystals

“…In Figure 3c, we report the temperature dependence of the rotating entropy change (∆S R ), associated with the rotation by an angle of 90 • of HoMn 2 O 5 (in the cb-plane) and TbMn 2 O 5 (in the ca-plane) between their easy and hard-axes. ∆S R can be written as ∆S R = ∆S (H//easy-axis) − ∆S (H//hard-axis) [1], where ∆S (H//easy-axis) and ∆S (H//hard-axis) are the entropy changes resulting from the application of the magnetic field along the easy and hard-axes, respectively. Both quantities can be well calculated from isothermal magnetization curves using the Maxwell relation since the hysteresis effect in these multiferroic materials is negligible [32,33].…”

“…Functional magnetocaloric materials at room temperature have attracted worldwide interest over the last two decades due to their potential implementation as refrigerants in magnetic cooling systems [1][2][3][4][5][6][7][8][9][10][11][12][13]. However, the search for materials with excellent magnetocaloric properties in the temperature range from about 2 to 30 K is of great interest from fundamental, practical, and economical points of view, due to their potential use as refrigerants in several low temperature applications such as the space industry, scientific instruments, and gas liquefaction [14][15][16][17][18][19][20][21][22][23][24][25].…”

“…Consequently, a large MCE could be obtained by rotating them between their easy and hard-axes in constant magnetic fields (Figure 1), instead of the conventional magnetization-demagnetization process (via field variation) [15,16,30,31]. This would enable the implementation of more compact and efficient magnetic refrigeration devices with a simplified design [1,15,16]. However, as presented below, the RMCE shown by the RMn2O5 oxides markedly depends on the rare earth element.…”

Large magnetocaloric effect of NdGa compound due to successive magnetic transitions

“…[1][2][3][4][5] To improve the application of this cooling technology, many efforts have been made to explore advanced MCE materials. The performance of MCE materials is usually evaluated by magnetic entropy change (∆S M ), refrigeration temperature width (δT FWHM ) and refrigeration capacity (RC).…”

Direct and indirect measurement of the magnetocaloric effect in bulk and nanostructured Ni-Mn-In Heusler alloy

“…About 30% of world's electricity consumption is used in refrigeration and air-conditioning systems. 1 Magnetocaloric effect (MCE) is the thermal response of a magnetocaloric material (refrigerant) under the effect of an external magnetic field. Although caloric effect can be obtained in solid state materials by manipulating their degree of freedom such as electric polarization (i.e.…”