  A Heat Flux Sensor (HFS) facilitates the visualization of heat flow, unlike a
temperature sensor, and is anticipated to be a key technology in managing waste
heat. Recently, an HFS utilizing the Anomalous Nernst Effect (ANE) has been
proposed garnering significant interest in enhancing the transverse Seebeck
coefficient. However, ideal materials for HFS not only require a large
transverse Seebeck coefficient but also meet several criteria including low
thermal conductivity and a bipolar nature of the transverse Seebeck
coefficient, especially a negative coefficient. In this study, we have
investigated ANE in amorphous ferrimagnetic GdCo alloys, revealing their
numerous advantages as HFS materials. These include a large transverse Seebeck
coefficient, extremely low thermal conductivity, large negative sensitivity,
unparalleled bipolar sensitivity, versatility for deposition on various
substrates, and a small longitudinal Seebeck coefficient. These qualities
position GdCo films as promising candidates for the advancement of HFS
technology.
