Ferrimagnetic relaxations in YIG versus frequency and temperature

Considerable interest in broadband microwave devices incorporating magnetized ferrites has developed in recent years. To facilitate the developments of these devices, the knowledge of ferrite loss parameters (ΔH, ΔHeff, ΔHk) is required over a large range of frequencies and temperatures. These data are also needed to better understand the basic physics of relaxation in polycrystalline ferrites. We report here on systematic wideband ΔH = f (ω,T) measurements on polycrystalline YIG, between 1 and 18 GHz and between - 100 and + 300C. This technique is supposed to allow the separation of the anisotropy and porosity induced contributions in narrow linewidth ferrites. Our data indicate that the microwave losses in ultra-low loss Ca-V-In or Gd-Al-Co substituted YIG are not completely resolvable in terms of these two known processes. The influence of other processes, such as magnetostriction relaxation and surface roughness contributions, appear to be negligible in the case of pure YIG.