Spin wave resonance in iron

Abstract

The spin wave spectra obtained from thin films of the iron group metals are discussed, mainly with reference to the spectrum of iron. It is found that, under suitable growth conditions, specimens can be manufactured whose resonance absorption modes are very similar to those predicted by the simple model of spin wave resonance. Three iron films are examined whose thicknesses range from 1800 to 4200 Å and all give similar values for the spin wave coupling constant D . The constant D is examined as a function of temperature and is found to behave in a similar way to nickel and cubic cobalt, giving a 10 % variation of D between 20 and 300 °K. A logarithmic plot indicates that a T5/2 law is obeyed for most of the temperature range, but it is also possible to fit the points to a T 2 plot, in accord with the itinerant electron model, provided other power law terms are assumed present. These other terms might be the spin wave interaction T5/2 term or that due to the effect of thermal expansion. The linewidths observed in the iron resonances are discussed, and reasons based on the ineffectiveness of the two magnon scattering processes are put forward for these narrow lines ( ~ 37 Oe) as opposed to the much broader lines often found in ferromagnetic resonance.