Enhancement of giant refrigerant capacity in Ho$_{1-x}$Gd$_{x}$B$_{2}$ alloys (0.1 $\leq$ x $\leq$ 0.4)

TL;DR

This study enhances the magnetocaloric properties of HoB$_{2}$ alloys by Gd substitution, resulting in higher refrigerant capacity and broader temperature range, suitable for cryogenic refrigeration.

Contribution

It demonstrates that Gd substitution in HoB$_{2}$ improves refrigerant capacity and extends the thermal working range, a novel approach for cryogenic cooling materials.

Findings

Gd enters HoB$_{2}$$ in a stoichiometric and random manner.

Gd addition increases Curie temperature and broadens magnetic entropy change.

The alloys show high refrigerant capacity and potential for cryogenic applications.

Abstract

Intending to optimize the giant magnetocaloric properties of HoB$_{2}$, we synthesized and magnetocalorically characterized Ho$_{1-x}$Gd$_{x}$B$_{2}$(0.1 $\leq$ x $\leq$ 0.4) alloys. We found out that Gd enters stoichiometrically and randomly into the Ho site, leading to a Vegard-type structural change. The addition of spherical S$^{7/2}$ Gd$^{3+}$ moments prompts an enhancement in Curie temperature, a reduction in peak value of the magnetic entropy change while still being relatively high, and a broadening of the magnetic entropy change curves. The overall influence is a relatively high refrigerant capacity and relative cooling power, and an extension of the thermal working range to higher temperatures; thus, electing Ho$_{1-x}$Gd$_{x}$B$_{2}$(as potential candidates for cryogenic refrigeration applications.