Glassy dynamics in magnetization across the first order ferromagnetic to antiferromagnetic transition in Fe0.955Ni0.045Rh.

We present the results of magnetization relaxation measurements across the ferromagnetic to antiferromagnetic transition in Fe(0.955)Ni(0.045)Rh. The transition from the high temperature ferromagnetic phase to the low temperature antiferromagnetic phase seems to be arrested by increasing the applied magnetic field. The crossover from crystallization-like dynamics to glassy dynamics can be tracked by measuring isothermal time dependent magnetization at various constant temperatures while cooling across this ferromagnetic to antiferromagnetic transition. The initial conversion from the ferromagnetic to antiferromagnetic phase as a function of time at higher temperatures follows a distinct power law relaxation. The transition is incomplete at low temperatures with the stretched exponential relaxation behaviour dominating over the power law, which is indicative of glassy dynamics or the arrest of the kinetics of the phase transition. In the intermediate temperature regime, the magnetic relaxation can be explained as a combination of both the power law and stretched exponential. The temperature dependence of the time constant of the stretched exponential follows the Arrhenius law which is usually observed in the case of strong glass-forming liquids.