Synthesis and characterization of vertically aligned La0.7Sr0.3MnO3:NiO nanocomposite thin films for spintronic applications

TL;DR

This study demonstrates how microstructural tuning of La0.7Sr0.3MnO3:NiO nanocomposite thin films via pulsed laser deposition enhances their magnetic and electronic properties, advancing their potential for spintronic device applications.

Contribution

It introduces a method to control the microstructure of VAN thin films and links this to improved magnetic and electronic functionalities relevant for spintronics.

Findings

Microstructure can be tuned from nano-granular to nano-maze.

Enhanced magnetoresistance observed over 10-240 K.

Perpendicular exchange bias field up to 230 Oe.

Abstract

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. Here, we show how the microstructures in self-assembled VAN thin films of La0.7Sr0.3MnO3:NiO (LSMO:NiO) can be effectively tuned from nano-granular to nano-columnar, and to nano-maze by controlling the number of laser shots from the two constituent phase targets in the pulsed laser deposition (PLD) film growth. The observed microstructural induced strain is found to significantly enhance the magnetoresistance in a very broad temperature range between 10-240 K and to modulate the in-plane exchange bias (EB), with the largest EB value observed in the maximally strained heterostructures. Most interestingly, a unique perpendicular exchange bias (PEB) effect is also observed for these heterostructures with an enhanced PEB field of up to 230 Oe. X-ray magnetic circular dichroism and training effect measurements demonstrate that the observed EB is disorder-induced and arises due to the pinning of NiO uncompensated moments at the disordered interface which is ferromagnetically coupled with LSMO. Furthermore, systematic changes in the electronic structure across the vertical interface related to a variation of the Mn3+/Mn4+ content arise as a consequence of out-of-plane tensile strain.