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 (ΔT_ad 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 Gd_1-xR_x alloys, LaFe_13-xSi_x, MnFeP_1-xAs_x, and R_1-xA_xMnO₃ (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.

Magnetic and magnetocaloric properties of HoMn₂O₅ single crystals were investigated. HoMn₂O₅ undergoes a large conventional magnetocaloric effect around 10 K. The magnetocaloric effect was found to present a giant anisotropy. Consequently, a large magnetocaloric effect (−ΔS_R,_max= 12.43 J/kg K for 7 T) can be obtained simply by rotating the single crystal HoMn₂O₅ within the cb plane in constant magnetic field instead of moving it in and out of the magnetic field zone. This can open the way for the implementation of compact, simplified, and efficient rotary magnetic refrigerators.

Recently, a so-called “colossal” magnetocaloric effect (MCE) was reported in ${\text{Mn}}_{1-x}{\text{Fe}}_x\text{As}$ [A. de Campos et al., Nat. Mater. 5, 802 (2006)]. However, the value of $\Delta S$ that was determined appears markedly overestimated since it results from the inadequate use of the Maxwell relation. Here, we report on recent measurements of $\Delta S$ in ${\text{Mn}}_{1-x}{\text{Fe}}_x\text{As}$ from which a correct MCE value is deduced by using the Clausius–Clapeyron equation. This result is asserted by careful use of the Maxwell relation.

In conventional magnetocaloric refrigeration systems, the magnetocaloric effect is exploited by moving the active material in and out of the magnetic field source. Here, we demonstrate that a large and reversible magnetocaloric effect (−ΔS_R, max = 6.4 J/kg K and ΔT_R, max = 8 K under 2 T) can be generated simply by rotating the multiferroic TbMn₂O₅ single crystal around its b axis in a relatively low constant magnetic field applied in the ac plane. Our results should inspire and open ways toward the implementation of compact, efficient and embedded magnetocaloric devices for low temperature and space applications.

It is known that some of RMnO3 and RMn2O5 (R = rare earth) multiferroic crystals reveal a strong interplay between their magnetic and electric order parameters, paving the way for applications in spintronic technologies. Additionally, recent works have also pointed out their potential utilization as refrigerants in magnetocaloric cooling systems for cryogenic tasks. In this paper, recent advances regarding the magnetocaloric properties of both RMnO3 and RMn2O5 families of multiferroics are reviewed. With the aim of understanding the RMnO3 and RMn2O5 magnetocaloric features, their structural and magnetic properties are discussed. The physics behind the magnetocaloric effect as well as some of its key thermodynamic aspects are also considered.