Correlating the local magnetic properties of the magnetic phase transition in Gd₅Ge₄ using scanning Hall probe imaging

Abstract

We present a study of scanning Hall probe imaging on a bulk sample of the prototype giant magnetocaloric material Gd₅Ge₄ across the magnetic field-induced antiferromagnetic to ferromagnetic and the reverse ferromagnetic to antiferromagnetic transitions at 35 K. We confirm that the sample presents phase coexistence of both antiferromagnetic and ferromagnetic phases through the crossover region in the field-temperature plane indicative of the first order nature of the phase transition. By studying the features of the local magnetization-field loops corresponding to the pixel size of 30 μm×30 μm across the entire image region we show that the two magnetic transitions are not spatially symmetric and, therefore, are not governed entirely by static inhomogeneity. Our work adds further support to the idea that random strain fields play a considerable role in defining the magnetic behavior across the field driven transition.