Understanding the large rotating magnetocaloric effect in TbMn1-xFexO3 single crystals upon q-Fermi Dirac nonextensive statistics

Abstract

In magnetic materials, a large magnetocaloric effect is expected in those with large magnetocrystalline anisotropy in the vicinity of their magnetic phase transition temperature. Here we report a comparative study of rotating magnetocaloric effect in TbMn1-xFexO3 (x = 0, 0.75) single crystals by rotating them in a constant external field within ac plane from 2 to 50 K. We observed a large magnetic entropy change between a and c axes with strong magnetocrystalline anisotropy in TbMnO3 as well as TbMn0.25Fe0.75O3. For TbMn0.25Fe0.75O3, the large magnetocaloric effect appears close to a spin reorientation from Γ1(Ax,Gy,Cz) to Γ4(Gx,Ay,Fz) magnetic configuration at ∼16 K, which is distinguished from that of TbMnO3 near the antiferromagnetic ordering of Tb3+ ions at ∼9 K. The maximum of magnetic entropy change and refrigerant capacity of TbMnO3 (TbMn0.25Fe0.75O3) reach as high as 19.20 J/Kg K (14.84 J/Kg K), 411.97 J/Kg (260.80 J/Kg) under 7 T, respectively. Furthermore, using Lorentz transmission electron microscopy technique, we show the TbMn0.25Fe0.75O3 material displays a large single domain structure with dimension up to about 3 μm×3 μm, as an indicative of a large magnetocrystalline anisotropy in this system. Based on nonextensive thermodynamics, we further employ the q- Fermi Dirac statistics to demonstrate the good consistency between computed and experimental results of magnetization versus rotating angles. Our results clearly indicate the magnetocrystalline anisotropy energy plays a decisive role in the large differences of the magnetic properties and magnetocaloric properties in TbMn1-xFexO3 system.