Substrate-Driven Stabilization of Perpendicular Magnetic Anisotropy and Near-Room-Temperature Ferromagnetism in Cr-Rich Cr_1+δTe₂ Films

Thin films of Cr-rich self-intercalated Cr_1+δTe₂ two-dimensional (2D) ferromagnet typically exhibit high Curie critical temperature (<i>T</i> _C) with in-plane magnetic anisotropy. In this work, we show that high quality Cr-rich (δ = 0.76) Cr_1+δTe₂ films grown on Si/InAs substrates by molecular beam epitaxy, at high temperature, exhibit a new magnetic phase combining perpendicular magnetic anisotropy (PMA) with a near-room-temperature Curie temperature (<i>T</i> _C ≈ 260 K), albeit with slightly reduced saturation magnetization, as evidenced by SQUID and magneto-optical Kerr effect magnetometry. The new phase manifests itself by a characteristic Moiré pattern as revealed by scanning tunneling microscopy and is associated with a contraction of the <i>c</i>-axis by 0.08 Å, as evidenced by X-ray diffraction, which are both attributed to indium diffusion and segregation at the surface. First-principles calculations indicate a noncollinear magnetic moment configuration that can be attributed to nearest-neighbor interlayer antiferromagnetic exchange interaction. This configuration shifts toward increased collinearity as the <i>c</i>-axis contracts and is attributed to the strengthening of the ferromagnetic exchange interaction which favors PMA. This work highlights that it is possible to influence the magnetic state of 2D chromium telluride ferromagnets, using suitable substrates and growth parameters to obtain PMA at nearly room temperature, which is desirable for future spintronics and prospective magnetic memories applications.