Tuning antiferromagnetic interlayer exchange coupling in La0.67Ca0.33MnO3-based synthetic antiferromagnets

Synthetic antiferromagnets (S-AFMs) composed of strongly correlated oxides have recently been demonstrated to show potential applications in spintronic devices. However, the tunability for the interlayer exchange coupling (IEC) in these all-oxide S-AFMs remains unclear. Here, we report that the IEC in La0.67Ca0.33MnO3/CaRu1-xTixO3 [LCMO/CRTO(x), (0 ≤ x ≤ 0.5)] superlattices (SLs) grown on NdGaO3 (NGO) substrates can be tuned via altering the composition of the spacer layer as well as the growth orientation. The IEC changes from ferromagnetic to antiferromagnetic (AF) type upon doping the spacer CRO with Ti. As the Ti doping level (x) increases, the AF-IEC field (Hex) peaks at x = 0.2, while the Curie temperature (TC) and coercivity (HC) decrease monotonously. Also, we find that the SLs grown on NGO(110) substrates possess larger Hex and smaller HC compared with those grown on NGO(001). Based on these observations, we further fabricate a “hybrid” heterostructure in the form of CRO/LCMO/CRTO(x = 0.5)/LCMO/CRO. Thanks to the collective roles of CRO and CRTO layers, the AF-IEC is maintained and meanwhile the TC is greatly enhanced. The observed high tunability of AF-IEC in LCMO-based S-AFM can primarily be ascribed to the highly tunable properties of the oxide constituents in the AFMs, which are sensitive to both the chemical composition and the growth orientation. Our work paves a way to control the AF-IEC behavior in all-perovskite-oxide S-AFMs, and the results may be instructive to the design of oxide spintronic devices.