Thermal spike model applied to the irradiated yttrium iron garnet: Mean diffusion length of the energy deposited on the electrons

Single crystals of yttrium iron garnet Y3Fe5O12 have been irradiated with 270 MeV 52Te, 760 MeV 86Kr and 1040 MeV 208Pb ions. The extent of the induced damage is determined using Rutherford backscattering spectrometry (RBS) in channeling geometry with a 2 MeV 4He beam. Taking into account these new results and the previous ones, the thermal spike model was applied to calculate track radii versus electronic stopping power for different beam energies using only one fitting parameter, λ the mean diffusion length of the energy deposited on the electrons by the slowing down of a swift heavy ion in the garnet. As the latent heat of fusion is unknown for yttrium garnet, the calculation was first performed by neglecting it. A λ value of (6.3 ± 0.3) nm is extracted by fitting all the different results taking into account a velocity effect. Such a λ value is the high limit of the mean diffusion length since it decreases if the latent heat of fusion is not neglected. This value of λ is in agreement with the previous determinations made in the same conditions for resistant insulators, showing that λ should decrease when the band-gap energy increases.