Rotating Magnetocaloric Effect in First-order Phase Transition Material Gd5Si2Ge2

Abstract

The rotating magnetocaloric effect (RMCE) induced by self-demagnetization has been investigated in the giant magnetocaloric effect (GMCE) material Gd${}_5$Si${}_2$Ge${}_2$. This shape-dependent effect had thus far only been reported in pure Gd, marking this as the first analysis of the effect in a sample with a magnetostructural first-order phase transition. By rotating the applied magnetic field vector while keeping its intensity constant, the demagnetizing field within a high-aspect ratio sample changes significantly, resulting in a RMCE. We characterize RMCE by determining the adiabatic temperature change ($\hat{I}”T_{ad}^{rot}$) directly through temperature measurements, and the isothermal entropy change ($\hat{I}”S_M^{rot}$) via magnetometry and magnetostatic simulations. We obtain a remarkable maximum $\hat{I}”T_{ad}^{rot}$ of 1.77 K for a constant external field of 0.8 T, higher than that obtained under 1.0 T. The magnetostatic simulations not only corroborate the highly non-monotonous field-dependence of $|\hat{I}”S_M^{rot}|$, which reaches 95\% of its maximum value at 0.8 T, 6.12 J K${}^{-1}$ kg${}^{-1}$ for the experimentally measured shape, but also estimate a 35\% increase in the maximum $|\hat{I}”S_M^{rot}|$ up to 8.67 J K${}^{-1}$ kg${}^{-1}$ in a simulated shape with higher aspect ratio.

18 pages, 10 figures. To be submitted for peer review