Phase coexistence and metastability in polycrystallinePr0.2La0.8Fe11.4Al1.6 compound

Abstract

Electrical resistivity, dc magnetization, ac magnetic susceptibility, and magnetic relaxation studies ofpolycrystalline Pr0.2La0.8Fe11.4Al1.6 compound have been carried out. On the basis of the measurements ofisofield magnetization and ac magnetic susceptibility, we provide evidencefor phase coexistence (the appearance of the ferromagnetic phase in theantiferromagnetic matrix) rather than a spin glass, resulting in a cusp observed at∼70 K in the zero-field-cooled thermal magnetization curve under low fields. The ferromagneticclusters or nuclei appear randomly in the antiferromagnetic matrix according to theelectrical resistivity results. An excellent magnetic–resistive correspondence is observedunder medium fields. Under these fields large relaxation effects are presented inthe vicinity of the phase transition temperature. Nonuniform variation of therelaxation rate with temperature gives a clear picture of the nucleation and growthof phases. Distinct metastable behavior is shown during the phase transition,which brings about the step-like behavior in the various magnetization curves.