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arXiv · 2610.01714

Complex magnetic phase diagrams in Tb$_2$IrAl$_4$Ge$_2$ and Er$_2$IrAl$_4$Ge$_2$

Karolina Gornicka·Matthew S. Cook·Brenden R. Ortiz·Andrew D. Christianson·Andrew F. May
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Abstract

We report the synthesis and comprehensive investigation of single-crystalline Tb$_2$IrAl$_4$Ge$_2$ and Er$_2$IrAl$_4$Ge$_2$, the first Ir-based members of the $Ln_2M$Al$_4$Ge$_2$ family. Both compounds crystallize in the tetragonal Tb$_2$NiAl$_4$Ge$_2$-type structure (space group $I4/mmm$) and exhibit easy-axis magnetic anisotropy with the crystallographic $c$ axis as the preferred magnetization direction. Tb$_2$IrAl$_4$Ge$_2$ undergoes antiferromagnetic ordering below $T_N = 25$ K and develops a sequence of field-induced metamagnetic transitions accompanied by pronounced magnetotransport anomalies, including a nonlinear Hall response. In contrast, Er$_2$IrAl$_4$Ge$_2$ exhibits three successive zero-field magnetic transitions and a substantially richer low-temperature magnetic phase diagram comprising multiple competing field-induced phases confined to relatively modest magnetic fields. The differences between the Tb- and Er-based compounds demonstrate the wide range of magnetic behavior that can be realized within the \ce{Tb2NiAl4Ge2}-type structure. More broadly, the successful realization of Ir-based $Ln_2M$Al$_4$Ge$_2$ compounds considerably expands the accessible chemical space of this family and opens a route toward the exploration of related $4d$- and $5d$-based aluminogermanides.

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Karolina Gornicka, Matthew S. Cook, Brenden R. Ortiz, Andrew D. Christianson, Andrew F. May. 2026-10-01. Complex magnetic phase diagrams in Tb$_2$IrAl$_4$Ge$_2$ and Er$_2$IrAl$_4$Ge$_2$. https://doi.org/10.1103/jjjk-3hf3

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