Characterizing the Relationship Between Temperature and Anisotropic Magnetoresistance in Manganite Thin Films

Manganite thin films have been extensively studied for their wide range of potential applications in solid-state data storage and correlated electron devices. One lesser-explored property of manganites is anisotropic magnetoresistance (AMR), or electrical resistance that changes as a function of the angle between the manganite sample and an applied magnetic field. AMR can reveal certain underlying phenomena in magnetic materials and is also relevant for potential applications. We develop a convenient method for measuring the AMR of thin film samples using a home-built cryostat, which allows for large sample sizes, and a LabView program to collect data. Then, we investigate the dependence of AMR on temperature in a La_0.7Ca_0.3MnO₃ (LCMO) thin film and analyze it using a phenomenological model. We find that there is an overall inverse relationship between sample temperature and resistance anisotropy with the exception of one anomalous temperature at 100 K. We present a possible explanation for this relationship, wherein competing ferromagnetic metallic and insulating phases within the material lead to the temperature dependence of AMR in LCMO.