Invar behavior of NANOPERM-type amorphous Fe–(Pt)–Zr–Nb–Cu–B alloys

Transmission Mössbauer spectra of amorphous Fe86Zr7Nb1Cu1B5, Fe81Zr7Nb1Cu1B10 and Fe81Pt5Zr7Nb1Cu1B5 alloys in the as-quenched state and subjected to the accumulative annealing for 15min in the temperature range from 573K up to 750K are presented. After these heat treatments the alloys remain in the amorphous state. The accumulative annealing for 15min at 573K and then 600K of the Fe86Zr7Nb1Cu1B5 and Fe81Zr7Nb1Cu1B10 alloys causes the narrowing of the transmission Mössbauer spectra as compared to the as-quenched state and the decrease of the average hyperfine field induction which is connected with the invar effect. For similar behavior in Fe81Pt5Zr7Nb1Cu1B5 alloy the accumulative annealing up to 700K is needed. With further increase of the annealing temperature up to 750K the broadening of the Mössbauer spectra and the increase of the average hyperfine field induction occur. The lowest value of the average hyperfine field induction of amorphous samples is accompanied by the lowest value of the Curie temperature. The investigated amorphous alloys do not reach the magnetic saturation up to the magnetizing field of 2T and the coefficient in Holstein–Primakoff term is about one order in magnitude larger than in other classical FeCo-based amorphous alloys due to the non-collinear magnetic structure. The Mössbauer spectra and hysteresis loops of the amorphous Fe86Zr7Nb1Cu1B5 alloy in the as-quenched state and after the accumulative annealing at 573+620K for 15min are sensitive to the tensile stresses subjected to the sample. Such behavior is ascribed to the invar anomalies. •Complex magnetic transformations found in the amorphous Fe86Zr7Nb1Cu1B5, Fe81Zr7Nb1Cu1B10 and Fe81Pt5Zr7Nb1Cu1B5 alloys.•Accumulative annealing within the amorphous state influences the hyperfine field parameters and Curie temperature.•The Mössbauer spectra and hysteresis loops in Fe86Zr7Nb1Cu1B5 alloy sensitive to the tensile stresses.