Dynamics of magnetic phase cluster formation in the field-driven AFM-FM transition in Gd5Ge4

Using a combination of local and global magnetometry, dimensional analysis and numerical simulations we investigate the dynamics of magnetic phase cluster formation across the first-order magnetic-field-driven magnetostructural transition in Gd5Ge4 at 6 K, where the transformation is completely irreversible, and at 35 K, where the reversibility is restored due to rising thermal fluctuations. We have previously shown, using scanning Hall probe images, that the transition involves phase separated clusters. Here we discuss these images in the context of a random nucleation and growth model, focusing on the relation between microscopic and macroscopic behaviours. The purpose of the work is to set up a framework for the analysis of these materials and it has implications for future discoveries of related functional magnetic materials where first-order, disorder-broadened transitions dominate key physical properties.