Magnetic, thermal, and magnetocaloric properties of the holmium trialuminide HoAl$_{3}$ with polytypic phases

TL;DR

This study explores the magnetic, thermal, and magnetocaloric behaviors of HoAl3 compounds with different crystal structures, revealing complex magnetic transitions and inverse magnetocaloric effects relevant for magnetic cooling applications.

Contribution

It reports the first detailed comparison of magnetic and magnetocaloric properties of polytypic HoAl3 phases with distinct crystal structures.

Findings

Trigonal phase exhibits antiferromagnetic transition at 9.8 K with inverse MCE.

Cubic phase shows antiferromagnetic order below 15 K, transitioning to a magnetic glassy state below 11 K.

Complex temperature and field dependence of MCE observed due to multiple magnetic states.

Abstract

We investigate the magnetic, thermal, and magnetocaloric properties of the intermetallic HoAl$_{3}$ compounds with two different crystal structures. The room-temperature equilibrium trigonal phase HoAl$_{3}$ undergoes an antiferromagnetic (AFM) transition at the Neel temperature $T^{\rm tri}_{\rm N} =$ 9.8 K. The AFM ordering of the compound is strong against the magnetic field, so that inverse magnetocaloric effect (MCE) is found even under a magnetic field change of 0-50 kOe. The high-pressure cubic phase HoAl3, prepared by a rapid-solidification process, is antiferromagnetically ordered below $T^{\rm cub}_{\rm N} =$ 15 K. Magnetic and specific heat measurements reveal that this long-range AFM state becomes unstable as the temperature drops and then it is replaced by a magnetic glassy state below a spin freezing temperature $T_{\rm f} =$ 11 K. The successive changes in magnetic state result in complicated temperature and field dependence of the MCE at low temperatures.