Tuning of exchange bias and magnetoresistance of self-assembled vertically aligned La_0.7Sr_0.3MnO₃:NiO nanocomposite thin films via microstructure induced strain

The microstructures and interfaces of two-phase vertically aligned nanocomposite (VAN) thin films play a key role in the design of spintronic device architectures and their multifunctional properties.[1,2] Here, we show how the microstructures in self-assembled VAN thin films of La0.7Sr0.3MnO3:NiO (LSMO:NiO) can be effectively tuned from nanogranular to nanocolumnar and to nanomaze by controlling the number of laser shots from the two constituent phase targets in the PLD film growth. The observed microstructural induced strain is found to significantly enhance the magnetoresistance in a very broad temperature range between 10 K and 240 K and to modulate the in-plane disorder-induced exchange bias, whose origin was investigated in detail by magnetotransport and X-ray magnetic circular dichroism measurements. As a consequence of out-of-plane tensile strain, a systematic variation in the Mn3+/Mn4+ content across the vertical interface is also observed by means of X-ray absorption spectroscopy. Our results [3] show that fine-tuning of the microstructure-induced out-of plane tensile strain, interfacial disorder and grain boundaries can be used to effectively modifying the exchange bias, magnetotransport and the electronic structural properties of these LSMO:NiO VAN thin films.