Magnetic characterisation and hydrogen absorption characteristics of Pr3(Fe,Ti)29Hx

Abstract An interstitial Pr3(Fe,Ti)29 hydride was synthesised by gas-phase hydrogenation on Pr3(Fe,Ti)29 powder using H2. The reaction kinetics between Pr3(Fe,Ti)29 and H2 gases was studied in a constant-volume reactor. The sample starts to rapidly absorb hydrogen, interstitially, at about 533 K. Absorption passes through a maximum at about 598 K (1.6 H/f.u) and then interstitial hydrogen desorption takes place up to the temperature of 673 K. By cooling to room temperature, the sample absorbs more hydrogen, interstitially, reaching the value of 3.6 H/f.u. By remaining at room temperature, the sample absorbs even more hydrogen reaching the value of 5.2 H/f.u. The lattice expansion observed is 2.1% and the Curie temperature, TC, increased from 392 to 518 K. The hydride exhibits saturation magnetisation, MS, of 145.4 and 157.5 Am2/kg at room temperature (RT) and at 5 K, respectively, anisotropy field, HA, of 2.1 T (RT) and 4.5 T (5 K) and average hyperfine field, Heff, of 23.3 T (RT). The magnetic anisotropy of Pr3(Fe,Ti)29 hydride is the same as that of the parent compounds, easy-cone-like, changing only in the cone angle (from 34° to 26°).