Superparamagnetism in CuFeInTe3 and CuFeGaTe3 alloys

The temperature dependencies of DC magnetic susceptibilities, χ(T), of CuFeInTe3 and CuFeGaTe3 alloys were measured in a SQUID apparatus using the protocol of field cooling (FC) and zero FC (ZFC). The FC curves of both samples reflect a weak ferromagnetic (or ferrimagnetic) behavior with a nearly constant value of χ(T) in the measured temperature range (2–300 K) indicating that the critical temperatures (Tc) are >300 K. The ZFC curves diverges from FC, showing irreversibility temperatures (Tirr) of ∼250 K for CuFeInTe3 and >300 K for CuFeGaTe3, suggesting that we are dealing with cluster-glass systems in a superparamagnetic state.