Spin-glass-like static and dynamic properties of mechanically alloyed Fe-Re-Cr

We report the observation of spin-glass-like features in a Fe61Re30Cr9 sample obtained after high energy milling for 460 h. X-ray diffraction showed a broad nanocrystalline peak. The zero-field-cooled and field-cooled magnetization curves exhibited a clear irreversibility, the former showing a relatively sharp maximum for low fields at T(max)approximate to 60 K. In addition, the temperature dependence of the magnetic AC susceptibility (chi(ac)) also showed a peak at approximately the same temperature. The frequency sensitivity of such maximum (p=Delta T-max/T(max)Delta log w approximate to 0.02) is small compared to that of typical superparamagnets. However, we discuss the insufficiency of this set of phenomena to assert the existence of a true spin-glass transition and propose the blocking of interacting ferromagnetic nanoparticles as the origin of the observed behavior. The effect of annealing, rendered into nanocrystallite growth, on the chi(ac) maximum is studied in an attempt to test this explanation. (C) 2000 American Institute of Physics. [S0021-8979(00)68708-X].