Nanocrystallization and magnetocaloric effect in amorphous Fe–Mo–Cu–B alloy

Abstract

Nanocrystallization revealed by X-ray diffraction, transmission electron microscopy and conventional Mössbauer spectroscopy in connection with specific magnetization versus temperature and magnetizing field induction and isothermal magnetic entropy change, as a measure of magnetocaloric effect, in the amorphous Fe76Mo10Cu1B13 alloy are studied. The annealing temperatures are chosen according to a DSC curve to fulfill conditions for the primary crystallization. There are no distinct changes in the crystallization process near the outer and inner surfaces of ribbons. The granular α-Fe phase with some Mo atoms incorporated into BCC lattice appears in the residual amorphous matrix. The grains diameter is almost independent of annealing temperature. The lattice parameter decreases on annealing and approaches to the value proper for pure bulk α-Fe. Such behavior is also confirmed by hyperfine parameters of the crystalline component. For all annealed samples in Mössbauer spectra analysis the component ascribed to the interface should be introduced even at early stages of crystallization. The Curie point of the amorphous phase is lower than the room temperature and increases on annealing. Such behavior makes the investigated material interesting for magnetic refrigerant application. The magnetic entropy change (ΔSM) is rather modest and has its maximum in the as-quenched state and distinctly decreases on annealing. ΔSM is analyzed qualitatively considering the different magnetic phases.