Magnetic Properties of FeSeTe Compound Crystallized from Liquid Phase

We report on measurements of samples with nominal composition $FeSe_{0.5}Te_{0.5}$, crystallized by the Bridgman method. Magnetic and transport properties of the samples were examined. The measurements confirm the coexistence of ferromagnetism and superconductivity below the superconducting transition temperature. The ferromagnetic contribution to magnetization, estimated at 10%, might be caused by the presence of ferrimagnetic $Fe_7Se_8$, which occupies about 10% of sample volume. From the Andreev spectroscopy we found superconducting energy gap Δ = 2.6 meV at T = 4.2 K, and from magnetization measurements the critical temperature $T_c$ = 15.8 K. The critical current density in magnetic field H = 4 kOe, determined from magnetization measurements, is $j_c$ = (1-2) × 1$0^4$ A/$cm^2$ and weakly depends on magnetic field intensity.