Department of Physics, Indian Institute of Technology Madras , Chennai 600036, India.
Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen Cedex, France.
ACS Appl Mater Interfaces. 2017 Oct 18;9(41):36423-36430. doi: 10.1021/acsami.7b11930. Epub 2017 Oct 5.
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.
氧化物异质结构的功能特性取决于容纳离子、自旋和结构不匹配的界面。在这里，通过稳定四方对称，我们在由两个铁磁体 SrRuO（SRO）和 PrMnO（PMO）组成的超晶格中实现了面内反铁磁（AFM）有序和双交换偏置。该超晶格系统的四方对称性是通过八面体旋转实现的，导致 c 轴参数伸长，Ru-O-Mn 键角接近 180°，从而诱导界面 AFM 有序，随着 PMO 层中 FM 有序的增加而被抑制。0.1 T 的面内冷却磁场（H）导致小磁滞回线沿负磁场轴的偏移（约-0.04 T），这是由于在 20 K 时存在-0.87 erg/cm 的 AFM 界面交换耦合能密度（E）。随着 H 的增加，交换偏置场（H）从负值变为正值。对于 5 T 的 H，H 为正值，但当 n ≤ 8（n = PMO 单位晶胞数）时，E 为-1.25 erg/cm，当 n ≥ 8 时，E 为 1.52 erg/cm。随着 H 的增加，H 从负值变为正值及其切换是由界面上强 AFM 耦合能和塞曼能相互作用解释的。结果表明，SRO-PMO 超晶格可能是研究功能氧化物界面交换耦合的模型系统。
