Analysis of the Anisotropic Magnetocaloric Effect in RMn2O5 Single Crystals

Abstract

Thanks to the strong magnetic anisotropy shown by the multiferroic RMn 2 O 5 (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 TbMn 2 O 5 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 R 3+ ions strongly affects their RMCEs. For example, the maximum rotating adiabatic temperature change exhibited by TbMn 2 O 5 is more than five times larger than that presented by HoMn 2 O 5 in a constant magnetic field of 2 T. In this paper, we mainly focus on the physics behind the RMCE shown by RMn 2 O 5 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 RMn 2 O 5 compounds through the modulation of exchange interactions via lattice distortions. This is a scenario that seems to be supported by Raman scattering measurements.

Synthesis and Room Temperature Structural, Optical, Electrical Properties of Holmium Doped GdMn2O5 Multiferroics

“…The graph shows that Gd 0.7 Ho 0.3 Mn 2 O 5 and Gd 0.6 Ho 0.4 Mn 2 O 5 exhibit a hardening tendency due to the volume contraction caused by the increased Ho 3+ content, and this corresponds to the Mn-Mn exchange striction. Such sort of hardening due to volume contraction was also reported by M. Balli et al 38 The sample Gd 0.8 Ho 0.2 Mn 2 O 5 showed softening behavior. This softening and hardening behavior of the samples promotes the spin-phonon correlation as the Ho +3 concentration increases in Gd 1-x Ho x Mn 2 O 5 .…”

The Anisotropic Magnetocaloric Effect and Size-Dependent Magnetic Properties of Iron Particles

“…The application of magnetocaloric materials, either ordinary or anisotropic, in magnetic refrigeration has been the subject of many papers [14,[18][19][20][21][22][23]; in particular, search for materials with magneto-volume coupling and first-order phase transition is currently an active research area. Other applications of MCE materials are in the domain of medicine, e.g., in treating hyperthermia and in drug delivery [15,[24][25][26][27][28], where nanoparticles could be used.…”