Phase coexistence and metastability in polycrystalline Pr(0.2)La(0.8)Fe(11.4)Al(1.6) compound.

Electrical resistivity, dc magnetization, ac magnetic susceptibility, and magnetic relaxation studies of polycrystalline Pr(0.2)La(0.8)Fe(11.4)Al(1.6) compound have been carried out. On the basis of the measurements of isofield magnetization and ac magnetic susceptibility, we provide evidence for phase coexistence (the appearance of the ferromagnetic phase in the antiferromagnetic 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 ferromagnetic clusters or nuclei appear randomly in the antiferromagnetic matrix according to the electrical resistivity results. An excellent magnetic-resistive correspondence is observed under medium fields. Under these fields large relaxation effects are presented in the vicinity of the phase transition temperature. Nonuniform variation of the relaxation rate with temperature gives a clear picture of the nucleation and growth of phases. Distinct metastable behavior is shown during the phase transition, which brings about the step-like behavior in the various magnetization curves.