Structural and magnetic changes in hydrogenated TiFe1−xNix alloys

Abstract A series of crystalline B2 and amorphous TiFe 1− x Ni x samples with different compositions and hydrogen loading ratios was characterized by XRD, VSM, TG, mass-spectrometry, and ¹H NMR in order to investigate possible correlations between the sample magnetization and hydrogen content. In crystalline samples, a reversible second-order phase transition from α-phase (B2 with soluble hydrogen) through a mixture of α- and s-phase (B19 TiFe 1− x Ni x H y ) into a pure s-phase was found. An increase of magnetization upon hydrogen loading was observed, depending on the concentration of iron in the samples. No unambiguous correlation between the hydrogen content and the saturation magnetization was found. The saturation magnetization of as-prepared amorphous samples was found to be significantly higher than in as-prepared crystalline ones. For both types of samples, magnetization remained high after dehydrogenation as well. Thermal desorption mass-spectra was found to strongly depend on composition, whereas structure, charging pressure, and H-content did not have tremendous effect. By ¹H NMR, enhanced relaxation due to strong magnetic moments was observed; however, by TEM the existence of Fe-clusters in hydrogenated samples could not be verified.