Magnetic properties of AlB$_2$-type holmium silicides and germanides

TL;DR

This study investigates the magnetic properties of HoSi$_{1.67}$ and HoGe$_{1.67}$ with AlB$_2$-type structures, revealing their antiferromagnetic order and how vacancy substitution influences magnetic entropy, aiding the development of rare-earth magnetic materials.

Contribution

It reports the synthesis and magnetic characterization of HoSi$_{1.67}$ and HoGe$_{1.67}$ with vacancies, highlighting how vacancy substitution affects magnetic order and entropy.

Findings

HoSi$_{1.67}$ has a Neel temperature of 17.6K.

HoGe$_{1.67}$ has a Neel temperature of 9.9K.

Replacing vacancies with nickel increases magnetic entropy changes.

Abstract

Discovery of the large magnetocaloric effect in HoB$_2$ has highlighted the practical advantage of heavy rare-earth ions. Other holmium compounds are of interest, and we here report the synthesis and the magnetic properties of HoSi$_{1.67}$ and HoGe$_{1.67}$ which form the same AlB$_2$-type structure but with vacancies. They are found to show the antiferromagnetic order with the Neel temperature 17.6(2)K for HoSi$_{1.67}$ and 9.9(2)K for HoGe$_{1.67}$, and the magnetic entropy changes at the temperature are 0.05(1)J/cm$^3$K for HoSi$_{1.67}$ and 0.08(1)J/cm$^3$K for HoGe$_{1.67}$. Magnetic orders were suppressed by replacing vacancies with nickel, resulting in an increase of magnetic entropy changes. Distance between the in-plane Ho$^{3+}$ ions appears to be an important parameter leading to the transition between the antiferromagnetic (HoSi$_{1.67}$) and the ferromagnetic (HoB$_2$) order. The finding may aid the exploration of other heavy rare-earth compounds for similar applications.