Ac linear and nonlinear susceptibilities, χ_(0) and χ_(2), of ferrimagnetic FeCr_(2)S_(4) 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 χ_(0) exhibits a cusp at around T_(m)≈60K correlated with the onset of dc magnetization irreversibilities. The imaginary part of χ_(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, χ_(0)~(′) and χ_(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, χ_(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 χ_(2)~(′) around T_(m) is observed. The field and temperature dependencies of χ_(0) and χ_(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.
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