A STUDY OF HYDROGEN DESORPTION FROM FE55CR25NI20, ALLOY BY MEANS OF FERROMAGNETIC-RESONANCE

FMR absorption in hydrogen-charged Fe55Cr25Ni20 austenitic alloys was measured versus temperature in the range of 4-200 K and at 77 K versus duration of hydrogen desorption caused by hearings at 293-393 K. Unde r the influence of hydrogen the FMR signal is shifted towards high mag netic fields, which provides evidence for the increasing role of s ele ctrons in the formation of the magnetic structure of the alloy, and br oadened, the latter effect being caused by the effective electron scat tering of the hydrogen atoms. The FMR intensity is found to be proport ional to the saturation magnetization and obeying the T-3/2-law at low temperatures (T much less than Theta(C), where Theta(C) is Curie temp erature). The activation enthalpy E(a) and the frequency factor omega( 0) were measured from the dependence of the integral intensity and the line width recorded at 77 K on the duration of desorption at various temperatures. The value of E(a) = 0.56+/-0.02 eV is consistent with th e data for hydrogen migration in the same alloy obtained by means of t he internal-friction technique while the value of the frequency factor omega(0) = (3.0 +/- 0.1) x 10(6) s(-1) reflects the peculiarities of the hydrogen-induced magnetic structure of the alloy. It characterizes the length of the spin correlation of s electrons which determines th e distance of hydrogen atom migration needed for a detectable change o f the magnetic structure during hydrogen desorption. The results indic ate the strong s-d exchange interaction between hydrogen s electrons a nd the host atoms.