Probing Magnetization Switching in Ferromagnet/Nonmagnet Bilayers Using Nonlinear Magnetoresistance and Anomalous Nernst Effect

The spin state of patterned magnets is crucial for various device applications and is typically probed by using magnetic imaging techniques with high spatial resolution. In this study, we demonstrate that both electrically induced nonequilibrium spins at ferromagnetic/nonmagnetic interfaces and the accompanying temperature gradient can serve as effective and convenient tools for detecting magnetization reversal processes in patterned magnetic thin films, a task that is challenging for conventional techniques. Focusing on Pt/CoFeB bilayers, we reveal that the nonlinear magnetoresistance caused by nonequilibrium spins at the Pt/CoFeB interface, along with anomalous Nernst effect, functions effectively as a built-in micromagnetometer. The proposed approach provides valuable insights into the magnetic properties of CoFeB deposited under various conditions that cannot be accessed through conventional anisotropic magnetoresistance measurements.