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 samp le obtained after high energy milling for 460 h. X-ray diffraction showed a broad nanocrystalline peak. The zero-field-cooled and field-cooled magneti zation curves exhibited a clear irreversibility, the former showing a relat ively sharp maximum for low fields at T(max)approximate to 60 K. In additio n, the temperature dependence of the magnetic AC susceptibility (chi(ac)) a lso showed a peak at approximately the same temperature. The frequency sens itivity of such maximum (p=Delta T-max/T(max)Delta log w approximate to 0.0 2) is small compared to that of typical superparamagnets. However, we discu ss the insufficiency of this set of phenomena to assert the existence of a true spin-glass transition and propose the blocking of interacting ferromag netic nanoparticles as the origin of the observed behavior. The effect of a nnealing, rendered into nanocrystallite growth, on the chi(ac) maximum is s tudied in an attempt to test this explanation. (C) 2000 American Institute of Physics. [S0021-8979(00)68708-X].