Magnetic characterisation and hydrogen absorption characteristics of Pr-3(Fe,Ti)(29)H-x

An interstitial Pr-3(Fe,Ti)(29) hydride was synthesised by gas-phase hydrog enation on Pr-3(Fe,Ti)(29) powder using H-2. The reaction kinetics between Pr-3(Fe,Ti)(29) and H-2 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 int erstitial hydrogen desorption takes place up to the temperature of 673 K. B y cooling to room temperature, the sample absorbs more hydrogen, interstiti ally, reaching the value of 3.6 H/f.u. By remaining at room temperature, th e sample absorbs even more hydrogen reaching the value of 5.2 H/f.u. The la ttice expansion observed is 2.1 % and the Curie temperature, T-C, increased from 392 to 518 K. The hydride exhibits saturation magnetisation, M-S, of 145.4 and 157.5 AM(2)/kg at room temperature (RT) and at 5 K, respectively, anisotropy field, H-A, of 2.1 T (RT) and 4.5 T (5 K) and average hyperfine field, H-eff, of 23.3 T (RT). The magnetic anisotropy of Pr-3(Fe,Ti)(29) h ydride is the same as that of the parent compounds, easy-cone-like, changin g only in the cone angle (from 34 degrees to 26 degrees). (C) 2001 Elsevier Science B.V. All rights reserved.