Ac susceptibility studies of ferrimagnetic FeCr2S4 single crystals

Ac linear and nonlinear susceptibilities, chi (0) and chi (2), of ferrimagn etic FeCr2S4 single crystals were measured in the temperature range from 4. 2 to 300 K for different driving ac and applied dc magnetic fields in the f requency range of 10(-1)-10(3) Hz. For high driving ac fields the real part of chi (0) exhibits a cusp at around T(m)approximate to 60 K correlated wi th the onset of dc magnetization irreversibilities. The imaginary part of c hi (0) shows a strong increase below 100 K and nonmonotonic temperature dep endence with a maximum shifted toward low temperatures with an increase in the driving field. Both real and imaginary parts of the linear susceptibili ty, chi (0)' and chi (0)', show a pronounced frequency dependence between 9 0 and 20 K with a maximal difference at around 60 K. Below the Curie temper ature the real part of the nonlinear susceptibility, chi (2), exhibits a br oad negative peak which is strongly shifted towards low temperatures with a n increase in the driving field. No clearly divergent behavior of chi (2)' around T-m is observed. The field and temperature dependencies of chi (0) a nd chi (2) are explained by domain wall pinning. Spin-glass-like magnetic a nomalies at temperatures below 60 K are attributed to changes in the domain structure and the appearance of additional pinning centers suggested to re sult from a structural lattice transformation. (C) 2001 American Institute of Physics.