Ac susceptibility studies of ferrimagnetic FeCr2S4 single crystals

Ac linear and nonlinear susceptibilities, chi (0) and chi (2), of ferrimagnetic 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 frequency 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 with the onset of dc magnetization irreversibilities. The imaginary part of chi (0) shows a strong increase below 100 K and nonmonotonic temperature dependence with a maximum shifted toward low temperatures with an increase in the driving field. Both real and imaginary parts of the linear susceptibility, chi (0)' and chi (0)', show a pronounced frequency dependence between 90 and 20 K with a maximal difference at around 60 K. Below the Curie temperature the real part of the nonlinear susceptibility, chi (2), exhibits a broad negative peak which is strongly shifted towards low temperatures with an 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) and chi (2) are explained by domain wall pinning. Spin-glass-like magnetic anomalies at temperatures below 60 K are attributed to changes in the domain structure and the appearance of additional pinning centers suggested to result from a structural lattice transformation. (C) 2001 American Institute of Physics.