Spin re-orientation induced anisotropic magnetoresistance switching in LaCo$_{0.5}$Ni$_{0.5}$O$_{3-\delta}$ thin films

TL;DR

This study demonstrates how strain-induced spin re-orientation in LaCo$_{0.5}$Ni$_{0.5}$O$_{3-delta}$ thin films can switch and tune anisotropic magnetoresistance, revealing complex magnetic and electronic interactions relevant for sensor applications.

Contribution

It reveals strain-tunable spin re-orientation and AMR switching in cobaltate-nickelate thin films, with detailed insights into magnetic states and charge transfer mechanisms.

Findings

AMR switches with strain and temperature

Co spin state transition below magnetic transition

Presence of Ni$^{2+}$ and Co$^{4+}$ ions evidencing charge transfer

Abstract

Realization of novel functionalities by tuning magnetic interactions in rare earth perovskite oxide thin films opens up exciting technological prospects. Strain-induced tuning of magnetic interactions in rare earth cobaltates and nickelates is of central importance due to their versatility in electronic transport properties. Here we reported the spin re-orientation induced switching of anisotropic magnetoresistance (AMR) and its tunability with strain in epitaxial LaCo$_{0.5}$Ni$_{0.5}$O$_{3-\delta}$ thin films across the ferromagnetic transition. Moreover, with strain tuning, we could observe a two-fold to four-fold symmetry crossover in AMR across the magnetic transition temperature. The magnetization measurements revealed an onset of ferromagnetic transition around 50 K, and a further reduction in temperature showed a subtle change in the magnetization dynamics, which reduced the ferromagnetic long-range ordering and introduced glassiness in the system. X-ray absorption and X-ray magnetic circular dichroism spectroscopy measurements over Co and Ni L edges revealed the Co spin state transition below the magnetic transition temperature leading to the AMR switching and also the presence of Ni$^{2+}$ and Co$^{4+}$ ions evidencing the charge transfer from Ni to Co ions. Our work demonstrated the tunability of magnetic interactions mediated electronic transport in cobaltate-nickelate thin films, which is relevant in understanding Ni-Co interactions in oxides for their technological applications such as in AMR sensors.