Probing magneto-thermoelectric transport in magnetic thin films using lock-in thermography under a varying DC offset

Abstract

Lock-in thermography (LIT) is a powerful tool for studying magneto-thermoelectric effects in magnetic materials. While most studies have focused on thick or bulk films with negligible DC offset-induced Joule heating, systematic studies of the DC offset effect in thin films have been lacking. Here, we investigate the anomalous Ettingshausen effect (AEE) in magnetic thin films, including Ni(10 nm), CoFeB(6 nm), and CoFeB(6 nm)/Ru(0.6 nm)/Ni(10 nm) synthetic antiferromagnets, using the LIT under varying DC offset and magnetic field conditions. We show theoretically that, instead of adversely affecting LIT measurements, an intentionally introduced DC offset with moderate magnitude facilitates the extraction of AEE signals, which is verified experimentally through measurement of hysteresis loops of different types of U-shaped samples. Our findings show LIT's potential for studying magneto-thermoelectric effects in single- and multilayer structures over a broad thickness range, beyond just thick films.