Proximity induced ferromagnetism in spin-orbit semimetal SrIrO₃

Magnetotransport - the change of the electric resistance with applied magnetic field - is a very powerful tool to investigate magnetism through electronic transport in ultrathin films. Magnetoresistance (MR) and the anomalous Hall resistance (AHR) in a ferromagnet directly depend on the magnetization of the ferromagnetic material as MR ≈ αH² - βM², and AHR ≈ γM; where α, β, γ are the proportionality constants and H, M are the external applied field and magnetization respectively. Here, we report the direct observation of strong intrinsic anomalous Hall effect with a Hall angle of ~ 0.8 % in a heterostructure consisting of SrIrO₃ (SIO), a strong spin-orbit coupled semi-metal [1] and a ferromagnetic insulator LaCoO₃ (LCO) [2], which limits the electronic transport exclusively to the SIO layer. Beside a hysteretic positive anomalous Hall resistance and butterfly shaped negative magnetoresistance, a four-fold magnetocrystalline anisotropy with magnetic easy axis along the [110] in-plane direction is observed below T_c ≈ 100 K [3]. The Magnetization M deduced from MR and AHR show similar field dependence and coercive field suggesting same origin of the both effects. Inserting four monolayers of insulating SrTiO₃ between SIO and the LCO completely suppresses T_c, evidencing proximity induced ferromagnetism in SrIrO₃.

[1] M. A. Zeb and H.-Y. Kee, Phys. Rev. B 86, 085149 (2012).

[2] D. Fuchs et al., Phys. Rev. B2007, 75, 144402

[3] A. K. Jaiswal et al., Adv. Mater. 34, 2109163 (2022).