Ferromagnetic Resonance of 3He-Irradiated Thin Metal Films

Abstract

Ferromagnetic resonance measurements at 9.5 Gc/sec were made on a number of films of pure iron, pure nickel, and alloys of iron and nickel (Permalloy) before and after 2-MeV 3He-particle irradiation. The 3He particle flux was about 3×1017/cm2 and, during irradiation, the film temperature did not exceed 81°C, as determined by thin-film thermocouples. The resonance field as a function of angle in the film plane, H0(θ), and the half-width, ΔH, were measured at room temperature. In general, H0 decreased (by about 2, 35, and 15 Oe for the iron, Permalloy, and nickel films, respectively) as a result of the irradiation, except for the composition range between 26% and 37% Ni where H0 increased. Also, the half-width generally decreased with irradiation and the half-width change was smallest for compositions around 76% Ni. The changes in H0 were different for films of a given set evaporated onto various substrates (soft glass, fused quartz, single-crystal quartz). Irradiating films in a saturating magnetic field, in the remanent state, and in the demagnetized state gave Hk's which were larger, the larger the magnetic induction of the film during irradiation. Irradiating a film (or reirradiating a previously irradiated film) in a magnetic field also rotated the easy axis of the film into the direction of the field applied during irradiation. The rotation of the easy axis was observed over the entire composition range from pure iron to pure nickel. The variation with composition of the values of Hk after irradiation agrees qualitatively with the values obtained by others using static techniques.