Automating Anisotropic Magnetoresistance Measurements to Probe Size-Dependent Magnetic Anisotropy in Manganite Microstructures

At specific low temperature ranges, manganites such as (La_1-y Pr_y )_1-xCa_xMnO₃ (LPCMO) experience coexisting ferromagnetic metallic (FMM), anti-ferromagnetic charge-ordered insulating (AFM-COI), and paramagnetic insulating (PMI) phases due to their perovskite (ABO₃) structure. These coexisting phases cause magnetic anisotropy (MA), the tendency to magnetize along a certain axis, and has applications in technologies such as magnetoresistive random access memory (MRAM). To measure MA on the scale of the ferromagnetic domains, we measure anisotropic magnetoresistance (AMR), the change in resistance depending on the angle between the electric and magnetic fields, of LPCMO microstructures since direct magnetization measurements are difficult at such small volumes. Our existing probe used for these measurements uses a Hall bar and manual rotation, which introduces inefficiency and inaccuracy. We constructed a new cryostat to automate this process using a stepper motor, an Arduino Nano, and LabVIEW. We then obtained AMR measurements for LPCMO samples fabricated using photolithography. Initial data on 20 × 120 μm² samples have shown that domain switching behavior followed a modified Kondorsky model. With the smaller 5 × 30 μm² samples we studied the size dependence of AMR and domain switching dynamics of phase separated manganites