Co-sputtered epitaxial growth of altermagnetic CrSb (0001) thin films on SrTiO3 (111) single crystal substrates

A class of antiferromagnets, altermagnets with non-relativistic spin-splitting energy bands, has garnered intense attention for its unique spin polarization and potential in spintronic devices. Fabricating epitaxial altermagnetic (AM) films is a prerequisite for realizing AM-based devices; yet, it remains challenging. Herein, we report two critical advances in the synthesis of altermagnetic CrSb films. First, we establish a comprehensive growth parameter phase diagram that quantitatively maps the Cr:Sb stoichiometry against substrate temperature and Cr target power, enabling deterministic growth of stoichiometric films (Cr:Sb ≈ 1:1) at moderate temperatures (∼360 °C) with optimized power (∼49 W). Second, we reveal a distinct epitaxial relationship for sputtered CrSb on Sb2Te3−δ (ST)-buffered (111)–SrTiO3 (STO) substrates that differs from molecular beam epitaxy grown counterparts, exhibiting CrSb [0001] || STO [111] (out-of-plane) and CrSb [101¯0] || STO [21¯1¯] (in-plane), as confirmed by x-ray diffraction. Energy-dispersive x-ray spectroscopy verifies a uniform elemental distribution, while atomic force microscopy confirms a smooth surface (root-mean-square roughness of 1.8 nm for 44.6 nm-thick films). Longitudinal resistivity as a function of temperature indicates metallic behavior in the CrSb/ST/STO (111) thin films with a residual resistivity ratio of ∼1.2. Magnetoresistance and Hall measurements exhibit butterfly-shape and loop-like hysteresis, respectively, confirming an observable anomalous Hall effect that persists up to ∼100 K. This phenomenon originates from a ferromagnetic (CrxSb1−x)2Te3 interlayer formed by CrSb/ST interfacial intermixing, as confirmed by transmission electron microscopy. These results demonstrate that DC magnetron sputtering enables fabrication of epitaxial CrSb thin films at relatively low substrate temperatures, ensuring compatibility with conventional magnetic metallic multilayers.