Antiferromagnetic Heusler Ru $_{2}$ MnGe Epitaxial Thin Films Showing Néel Temperatures up to 353 K

Structural and electrical transport properties were investigated for Heusler-type alloy Ru₂ MnGe thin films. Ru₂ MnGe films on MgO substrate were subjected to an in-plane compressive strain due to their small lattice mismatch (-0.7%), and exhibited enhanced antiferromagnetic transition temperature (T_N) up to 353 K, which is much higher than that of the bulk material (T_N = 316 K). In contrast, the films on MgAl ₂O ₄ were almost in a relaxed-strain state, and showed T_N close to the bulk value (304 K). It was also found that the T_N of Ru₂MnGe thin films on MgO exhibited oscillating behavior depending on c/a ratio. We argued that the next-nearest neighbor magnetic interactions (J₂) of Mn-Mn atoms has oscillated depending on the degree of strain in Ru₂MnGe, which contribute to the oscillating behavior of T_N against c/a.