Magnetothermodynamic Properties and Anomalous Magnetic Phase Transition in FeRh Nanowires

Thermal properties of submicrometer wires of Pd-doped FeRh alloys are evaluated from measurements of transport properties around the first-order antiferromagnetic to ferromagnetic phase transition. Recently, in a submicrometer wire of FeRh alloy, an asymmetric structure between heating and cooling processes was reported in the vicinity of the phase transition temperature. A system where finite-size effects appear is expected to show different magnetic and thermal properties from those in bulk and thin film. However, thermal or magnetization measurements are difficult to perform on samples with such a tiny volume. Here, we demonstrate a quantitative evaluation of thermal properties in thin films and submicrometer wires of B2-ordered Pd-doped FeRh alloy grown on MgO (001). Resistivity measurements on a series of wires with different widths reveal that the anomaly in the resistance change is enhanced in narrow wires. As the transport properties in submicrometer wires sensitively reflect those magnetic states, the entropy change and the irreversible energy loss during the first-order phase transition have been determined via resistance measurements. We find a larger energy loss in smaller samples where wider hysteresis loops appear in temperature-driven measurements. This method can be a probe to evaluate the finite-size effect induced by a restricted magnetic domain nucleation process during the phase transition.