AE-04: Spin-flop Coupling at La0.5Sr0.5FeO3/La0.7Sr0.3MnO3 Interfaces

Antiferromagnetic (AFM) spintronics has several advantages like high storage capacity and faster processing speed, but difficulties in controlling AFM moments impede its application. Spin-flop coupling is a promising interfacial phenomenon which can allow manipulation of AFM moments with modest applied magnetic field values and is characterized by perpendicular coupling between ferromagnetic (FM) and AFM moments. AFM La1-xSrxFeO3 (x=0 and 0.3) / FM La0.7Sr0.3MnO3 (LSMO) heterostructures remain one of the few perovskite oxide systems where spin-flop coupling has been demonstrated. Previous studies showed that robust spin-flop coupling observed in 6 unit cells (u.c.) La0.7Sr0.3FeO3 / 6 u.c. LSMO superlattices vanished once the layer thicknesses reached 18 u.c., as the magnetocrystalline anisotropy energy of the AFM layer overcame the spin-flop coupling strength [1]. In this study, epitaxial La0.5Sr0.5FeO3 (LSFO) / LSMO bilayers with similar thickness of LSMO (∼85 u.c.) and LSFO thicknesses varying from 10 to 50 u.c. were deposited on (001)-oriented (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 substrates to investigate the relationship between Sr-doping, magnetocrystalline anisotropy, and the critical thickness for spin-flop coupling. Soft X-ray absorption magnetic spectroscopy was performed to probe the exchange interactions between the FM Mn moments and the AFM Fe moments. X-ray magnetic linear dichroism (XMLD) measurements demonstrated that the spin-flop coupling strength decreased with increasing LSFO layer thickness, persisting at a thickness of 50 u.c. (∼20 nm), surpassing the La0.7Sr0.3FeO3 / LSMO system (Fig.1). Also, photoemission electron microscopy imaged the domain-by-domain correlation between the FM and AFM domains consistent with the perpendicular orientation dictated by spin-flop coupling. As LSFO/LSMO system allows to control AFM moments through spin-flop coupling over a greater LSFO thickness, it is desirable for AFM spin transport measurements.References: [1] Y. Takamura, F. Yang, N. Kemik, E. Arenholz, M. D. Biegalski, and H. M. Christen, “Competing interactions in ferromagnetic/antiferromagnetic perovskite superlattices,” Phys Rev B, vol. 80, no. 18, p. 180417, Nov. 2009, doi: 10.1103/PhysRevB.80.180417.