Local probing of arrested kinetics in Gd5Ge4

We present spatially localized magnetic relaxation measurements of the first-order magnetostructural transition in Gd 5 Ge 4 using a scanning Hall probe imaging technique. Relaxation measurements were performed at 6, 10 and 35 K to probe the field-increasing antiferromagnetic (AFM) to ferromagnetic (FM) transition and, when it can occur, the field-decreasing FM to AFM transition. We demonstrate that localized regions relax with time towards the ground state for a given field and temperature and observe different magnetic behaviours at the three measurement temperatures. In particular, the observed magnetic relaxation at 6 K is consistent with the idea of an arrested state at this temperature. Our scanning Hall probe imaging data give an insight into the phase nucleation and growth process of the martensitic-like magnetostructural first-order transition in Gd 5 Ge 4 .