The functional properties of oxide heterostructures depend on the interfaces accommodating ions, their spins, and structural mismatches. Here, by stabilizing tetragonal symmetry, we achieve the in-plane antiferromagnetic (AFM) ordering and dual-exchange bias in the superlattices consisting of two ferromagnets SrRuO (SRO) and PrMnO (PMO). The tetragonal symmetry of this superlattice system achieved after the octahedral rotations yield an elongation of the c-axis parameter with Ru-O-Mn bond angle close to 180°, induces an interfacial antiferromagnetic ordering, which is suppressed as the ferromagnetic (FM) ordering in the PMO layer increases. The 0.1 T in-plane cooling field (H) leads to the shift (ca. -0.04 T) of minor hysteresis loop along the negative field axis due to the presence of -0.87 erg/cm AFM interfacial exchange coupling energy density (E) at 20 K. The exchange bias field (H) switches from negative to positive value with the increase in H. For 5 T H, the H is positive, but the E is -1.25 erg/cm for n ≤ 8 (n = number of unit cells of PMO) and 1.52 erg/cm for n ≥ 8. The H and its switching from negative to positive with the increase in H are explained by the interplay of strong antiferromagnetic coupling energy and Zeeman energy at the interfaces. The results demonstrate that the SRO-PMO superlattice could be a model system for the investigation of the interfacial exchange coupling in functional oxides.

The breaking of orthorhombic to tetragonal crystal symmetry is realized by increasing the PrMnO3 layer thickness in the superlattices consisting two ferromagnets, SrRuO3 and PrMnO3. The octahedral rotation pattern is a+c−c− and a0a0c− type for the superlattices with orthorhombic and tetragonal phase, respectively, inferred in the simulated projected density of states. The 15% reduction in orbital occupancy due to the a0a0c− type octahedral rotation compared to that of the a+c−c− type suggests the presence of stronger antiferromagnetic (AFM) coupling. The larger orbital overlapping leads to a stronger spin–orbit coupling, associated with a shift of 42.8% of the minor in‐plane field cooled (FC) magnetic hysteresis loop(M(H)) along the magnetization axis in orthorhombic superlattices. While, minor in‐plane FC M(H) shifts along the field axis due to the strong AFM coupling in tetragonal superlattices. In field‐dependent magnetoresistance, the rotation of spins in the antiferromagnetically coupled interfacial layers is detected as a unique anomaly, which is stronger in the superlattices for the biased spins and tetragonal symmetry than the pinned spins and orthorhombic symmetry. The results demonstrate that the tuning of interfacial exchange coupling and spin‐dependent transport by controlling structural distortion could be used as a tool in fabricating modern spintronics‐based devices.

The design, fabrication, and performance of an apparatus for the deposition of complex oxides with highly uniform thicknesses at controllable deposition rates over large area, even on the native amorphous SiO layer of (001) oriented single crystal Si, are described. The apparatus makes use of the lateral port of a spherical chamber. The port is maintained at uniform temperature, and it houses a substrate heater. The deposition process is controlled by varying different parameters such as target-to-substrate distance, sputtering power, sputtering gas atmosphere, substrate temperature, and pulsed plasma growth. The system has been tested by growing a series of LaSrMnO thin films on Si. The systematic strain relaxation and thus the tunable magnetic properties along with the presence of high-quality surface morphology of the films indicate that the designed system could be used to fabricate different components of oxide electronics-based devices over larger area.

No abstract

A strong perpendicular magnetocrystalline anisotropy (PMA) in antiferromagnetically coupled SrRuO 3 (17 uc (unit cell))/PrMnO 3 (n uc) superlattices effectively reconstructs the interfacial spin ordering. The occurrence of significant anisotropic interfacial antiferromagnetic coupling between the Ru and Mn ions is systematically tuned by varying the PrMnO 3 layer thickness in ultrathin scale from 3 to 12 uc, which is associated with a rise in PMA energy from 0.28 × 10 6 to 1.60 × 10 6 erg/cm 3 . The analysis using the Stoner−Wohlfarth model and density functional theory confirm that the exchange anisotropy is the major contribution to the PMA. The superlattices with PrMnO 3 layer thickness ≥7 uc exhibit the tunneling-like transport of Ru 4d electrons, which is rather expected in the stronger antiferromagnetically coupled superlattices with thinner PrMnO 3 layer. Tunneling-like transport at thicker spacer layer in the SrRuO 3 −PrMnO 3 superlattice system is an unique feature of two ferromagnet-based superlattices. Our investigations show that the technologically important interfacial magnetic coupling, PMA, and tunneling magnetoresistance could be achieved in a periodically stacked bilayer and can be precisely manipulated by the size effect in ultrathin scale.