Relaxation of rare earth and cobalt ions in polycrystalline yttrium iron garnet

Relaxation at room temperature of rare earths and cobalt ions in ferrimagnetic garnets has been studied by measuring the three linewidths : ΔH, resonance linewidth, Δ H
eff
, effective linewidth, ΔH
K
, spinwave linewidth. These linewidths have been measured at 9 GHz Δ H
eff
, far from resonance, Δ H
k
in perpendicular and in parallel pumps. From experimental results, relations between ΔH, Δ H
eff
and Δ H
k
have been found which are in good agreement with the theory. The broadening δ (ΔH), due to the introduction of rare earths ions, allows the relaxation time τ (about 10
^-13
sec) of some rare earths ions to be deduced from Kittel's theory. At room temperature, this theory explains the gyromagnetic properties of Sm
³⁺
, Tb
³⁺
, Dy
³⁺
, Ho
³⁺
and Er
³⁺
ions. An adaptation of this theory allows us to explain also the behaviour of Gd
³⁺
ions. Relation between δ (ΔH) and the saturation magnetization 4π M
s
are explained for the Sm, Dy, Ho and Er ions by an extension of Kittel's theory, but this explanation is not unique.