Rotating Magnetocaloric Effect in First-order Phase Transition Material Gd5Si2Ge2

TL;DR

This study investigates the rotating magnetocaloric effect in Gd5Si2Ge2, revealing significant temperature and entropy changes due to shape-dependent demagnetization, with potential for enhanced magnetic cooling applications.

Contribution

First analysis of RMCE in a first-order magnetostructural transition material, demonstrating shape-dependent effects and potential for improved magnetocaloric performance.

Findings

Maximum $ riangle T_{ad}^{rot}$ of 1.77 K at 0.8 T

Non-monotonous $ riangle S_{M}^{rot}$ dependence on field

Simulated shape increase $ riangle S_{M}^{rot}$ by 35%

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 ($\Delta T_{ad}^{rot}$) directly through temperature measurements, and the isothermal entropy change ($\Delta S_M^{rot}$) via magnetometry and magnetostatic simulations. We obtain a remarkable maximum $\Delta T_{ad}^{rot}$ 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 $|\Delta S_{M}^{rot}|$, 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 $|\Delta S_{M}^{rot}|$ up to 8.67 J K$^{-1}$ kg$^{-1}$ in a simulated shape with higher aspect ratio.