Analysis of the Anisotropic Magnetocaloric Effect in RMn2O5 Single Crystals

Mohamed Balli,Dimitre Dimitrov,Patrick Fournier,Serge Jandl,Saber Mansouri

doi:10.3390/magnetochemistry3040036

Abstract

Thanks to the strong magnetic anisotropy shown by the multiferroic RMn2O5 (R = magnetic rare earth) compounds, a large adiabatic temperature change can be induced (around 10 K) by rotating them in constant magnetic fields instead of the standard magnetization-demagnetization method. Particularly, the TbMn2O5 single crystal reveals a giant rotating magnetocaloric effect (RMCE) under relatively low constant magnetic fields reachable by permanent magnets. On the other hand, the nature of R3+ ions strongly affects their RMCEs. For example, the maximum rotating adiabatic temperature change exhibited by TbMn2O5 is more than five times larger than that presented by HoMn2O5 in a constant magnetic field of 2 T. In this paper, we mainly focus on the physics behind the RMCE shown by RMn2O5 multiferroics. We particularly demonstrate that the rare earth size could play a crucial role in determining the magnetic order, and accordingly, the rotating magnetocaloric properties of RMn2O5 compounds through the modulation of exchange interactions via lattice distortions. This is a scenario that seems to be supported by Raman scattering measurements.

Highlights

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]
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]
It is worth noting that the fundamental mechanisms behind the coupling between the magnetic ordering, crystal structure, and magnetocaloric properties in RMn2O5 are still unclear

Summary

Introduction

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]. Matsumoto et al [14] have unveiled a reciprocating AMR magnetic cooling device which utilizes the Dy2.4Gd0.6Al5O12 (DGAG) compound as a working refrigerant This material exhibits a large specific heat which largely reduces its magnetocaloric effect (MCE) in terms of the adiabatic temperature change (1 to 2 K under 1 T) [14]. In this context, the RMn2O5 (R = magnetic rare-earth element) multiferroics seem to be alternative candidates for magnetocaloric tasks around 10 K [15,16,25,26,27,28,29]. The more ordered Tb3+ moments would reduce the magnetic part, and the total specific heat

Distinguished Features of the RMCE in RMn2O5

Materials and Methods

Conclusions