Proximity induced ferromagnetism in the spin-orbit semimetal SrIrO₃

The 5d iridium-based transition metal oxides (TMOs) of the Ruddlesden-Popper series Sr_n+1Ir_nO_3n+1 have gained huge and broad interest because of the strong spin-orbit coupling in these compounds favoring new or exotic quantum states. This has resulted in one of the most active and competitive front of condensed matter research. In contrast to the 3d TMOs, the electron-electron correlation strength is however generally too small in the 5d TMOs to yield e.g. ferromagnetism, limiting the field of practical applications of these materials. Recently, we succeeded to produce a ferromagnetic (FM) state in the spin-orbit semimetal SrIrO₃ (SIO) by proximity effect in contact with an FM insulator, LaCoO₃ (LCO) [1]. The FM state of SIO was selectively probed by electrical transport in SIO/LCO thin film heterostructures. A large intrinsic and positive anomalous Hall effect (AHE) appears for T ≤ 100 K and indicates magnetic ordering. The AHE shows unusually large coercivity below about 40 K, very likely caused by a strong pseudo-spin lattice coupling. The anisotropic magnetoresistance (AMR) displays four-fold magneto-crystalline anisotropy with in-plane <110>pc magnetic easy axis. In addition, the use of SrTiO₃ as a gate material allows for a non-volatile electric control opening new routes towards a more efficient spin manipulation. The proximity induced FM state in SIO is significantly enhanced for positive gate voltage V_g and strongly suppressed for V_g < 0. The anomalous Hall conductivity s_AHE and Hall angle Q_Hall varies strongly with V_g and can be increased by about 600%.





References

[1] A. K. Jaiswal, D. Wang, V. Wollersen, R. Schneider, M. le Tacon, D. Fuchs, Advanced Materials 34 (2022) 2109163.