Magnetic Proximity Effect in Oxide Heterostructures

The fabrication of spintronics devices, encompassing spin transistors and spin valves, requires complex multi-layer structures composed of varying magnetic materials. This complexity opens the possibility of myriad interface effects, one of which is the proximity effect. This fascinating effect is the phenomenon where one layer's physical characteristics influence the properties of another layer within the same structure. Manganite thin film heterostructures could be a suitable candidate for the in-depth investigation of these proximity effects as manganites are known to display emergent phenomena stemming from the dynamic interplay between charge, spin, orbital, and lattice degrees of freedom [1]. Its intriguing properties include colossal magnetoresistance and metal-insulator transitions, among others. These unique features result from the complicated interplay between charge carriers, spin ordering, and lattice distortions, with modulating influences from external stimuli, such as magnetic fields or electric fields.<br/>The physical properties of manganites, such as Sm_1-xSr_xMnO₃ (SSMO), can be significantly changed by varying the percentage of Sr doping. Depending on the doping ratio, SSMO can manifest as a ferromagnetic or antiferromagnetic magnetic phase or even a mixture of both magnetic phases [2]. The vast range of tunable phenomena owing to Sr concentration in SSMO underscores its scientific significance and makes it an interesting candidate for the study of various properties [3, 4]. In this study, we explored the magnetic proximity effect in SSMO bilayer and tri-layer heterostructures. First, we deposited a single layer of ferromagnetic metal (FMM) and an anti-ferromagnetic insulator (AFI) using the pulsed laser deposition (PLD) method on a SrTiO₃ (STO) substrate. Their magnetic properties were analyzed using a SQUID magnetometer, with the results aligning well with the previously reported data. Next, we deposited a bi-layer stack of FMM/AFI and a corresponding tri-layer structure of AFI/FMM/AFI on the STO substrate. We discovered a significant increase in magnetic moment across these structures, suggesting the magnetic proximity effect in the heterostructures as the primary cause. In a nutshell, the manganite heterostructures provide a promising platform for delving deeper into new electronic and magnetic phenomena at the interfaces.<br/><br/>[1] Y. Tokura, Reports Prog. Phys. <b>69</b>, 797 (2006).<br/>[2] Kurbakov et al., Journal of Physics: Condensed Matter.<b> 20</b>, 104233 (2008).<br/>[3] Bhagwati Prasad, et al.”, Advanced Materials <b>27</b>, 3079 (2015).<br/>[4] Bhagwati Prasad and M. G. Blamire, Appl. Phys. Lett<b>. 109</b>, 132407 (2016).