Magnetocaloric effect in Tb$_{31}$Co$_{69}$ and Dy$_{31}$Co$_{69}$ thin films deposited on Si substrates

TL;DR

This study investigates the structural, magnetic, and magnetocaloric properties of Tb$_{31}$Co$_{69}$ and Dy$_{31}$Co$_{69}$ thin films on silicon, revealing ferrimagnetic behavior and significant magnetocaloric effects near specific transition temperatures.

Contribution

It provides new insights into the magnetocaloric properties of these specific thin film compositions and their phase-dependent behaviors, which were not previously characterized.

Findings

Ferrimagnetic behavior observed in both films.

Identified compensation and Curie temperatures for amorphous and crystalline phases.

Significant magnetocaloric effects near transition temperatures.

Abstract

We present the structural, magnetic, and magnetocaloric properties of thin films with stoichiometry Tb$_{31}$Co$_{69}$ and Dy$_{31}$Co$_{69}$ deposited on naturally oxidized silicon Si (100) substrates. Samples with a thickness $d=50$ nm covered with a protective Au overlayer with a thickness $d_{\rm Au} =5 $ nm were produced using the pulsed laser deposition technique. X-ray diffraction analysis indicated the presence of crystallized Laves phases and amorphous phases in the prepared materials. Magnetization measurements as a function of temperature revealed ferrimagnetic behavior in both samples. We estimated the compensation temperature $T_{\rm comp}$ of the amorphous phase for Tb$_{31}$Co$_{69}$ at 81.5 K and for Dy$_{31}$Co$_{69}$ at 88.5 K, while we found the Curie temperature $T_{\rm C,\ Laves}$ of the crystallized Laves phases at 204.5 K and at 117 K, respectively. We investigated the magnetocaloric effect in a wide temperature range, covering $T_{\rm comp}$ of amorphous phases and $T_{\rm C,\ Laves}$ of crystallized Laves phases. The analysis for the magnetic field change of $\Delta \mu_0H=5$ T showed values of the magnetic entropy change of $-\Delta S_{\rm M}=4.9$ mJ cm$^{-3}$ K$^{-1}$ at $T_{\rm comp}$ and $-\Delta S_{\rm M}=6.6$ mJ cm$^{-3}$ K$^{-1}$ at $T_{\rm C,\ Laves}$ for Tb$_{31}$Co$_{69}$, while for Dy$_{31}$Co$_{69}$, we determined the values of $-\Delta S_{\rm M}=35$ mJ cm$^{-3}$ K$^{-1}$ at $T_{\rm comp}$ and $-\Delta S_{\rm M}=28$ mJ cm$^{-3}$ K$^{-1}$ at $T_{\rm C,\ Laves}$.