Hyperfine interactions and some thermomagnetic properties of amorphous FeZr(Cr)NbBCu alloys

In this research, we studied the magnetic phase transition by Mössbauer spectroscopy and using vibrating sample magnetometer for amorphous Fe_86-xZr₇Cr_xNb₂Cu₁B₄ (x = 0 or 6) alloys in the as-quenched state and after accumulative annealing in the temperature range 600-750 K. The Mössbauer investigations were carried out at room and nitrogen temperatures. The Mössbauer spectra of the investigated alloys at room temperature are characteristic of amorphous paramagnets and have a form of asymmetric doublets. However, at nitrogen temperature, the alloys behave like ferromagnetic amorphous materials. The two components are distinguished in the spectrum recorded at both room and nitrogen temperatures. The low field component in the distribution of hyperfine field induction shifts towards higher field with the annealing temperature. It is assumed that during annealing at higher temperature, due to diffusion processes, the grains of α-Fe are created in the area corresponding to this component. Both investigated alloys show the invar effect and the decrease of hyperfine field induction after annealing at 600 K for 10 min is observed. It is accompanied by the lowering of Curie temperature.