Epitaxial growth and transport properties of a metallic altermagnet CrSb on a GaAs (001) substrate

Abstract: A newly identified class of magnetic materials called altermagnets has attracted much attention due to the practical properties of spin-splitting bands akin to ferromagnets and small compensated magnetization akin to antiferromagnets. These features make them promising candidates for applications in spintronics devices. Among candidate materials, CrSb is promising because of its high ordering temperature (~705 K) and large spin-splitting energy; however, it is predicted that tuning the N\'eel vector requires additional symmetry breaking or a change in the easy magnetization axis. While applying epitaxial strain can modulate the symmetry, the selection of substrates with closely matched lattice constants for heteroepitaxial growth is limited for altermagnets, which generally have low crystal symmetry. Therefore, exploring the heteroepitaxial growth of altermagnet thin films on well-established, dissimilar crystal systems is valuable. (001)-oriented III-V semiconductors, which share group-V elements with the overgrown CrSb, offer an ideal platform because they are expected to have material compatibility with stable interfaces, as well as tunability of the buffer layer's bandgap and lattice constant by varying the atomic composition of their group-III and group-V atoms. In this study, we have achieved the molecular beam epitaxial growth of a CrSb ($\bar{1}10$) thin film on a GaAs (001) substrate by inserting thin FeSb ($\bar{1}10$) / AlAs (001) buffer layers. The in-plane epitaxial relationship is found to be CrSb [110] $|$ GaAs [110] and CrSb [001] $|$ GaAs [$\bar{1}10$], and epitaxial strain is also confirmed. We also characterized the magneto-transport properties of the grown CrSb thin film. Although the obtained conductivity tensors are mainly explained by a two-carrier model, not by an anomalous Hall effect, this model reveals the presence of high-mobility electron and hole carriers.