Damage processes and magnetic field orientation in ferrimagnetic oxides ${\mathrm{Y}}_3$${\mathrm{Fe}}_5$${\mathrm{O}}_{12}$ and ${\mathrm{BaFe}}_{12}$${\mathrm{O}}_{19}$ irradiated by high-energy heavy ions: A Mössbauer study

Mössbauer spectroscopy of damage induced by energetic Ar, Kr, and Xe ions in the giga-electron-volt range in two ferrimagnetic oxides, ${\mathrm{Y}}_3$ ${\mathrm{Fe}}_5$ ${\mathrm{O}}_{12}$ and ${\mathrm{BaFe}}_{12}$ ${\mathrm{O}}_{19}$, is presented. The enhancement of the paramagnetic phase observed after an irradiation with high-energy deposition (Xe and Kr ions) compared to low-energy deposition (Ar ions) supports a damage mechanism based on the electronic stopping power. Threshold energy-deposition values close to 17 and 25 MeV ${\mathrm{cm}}^2$ ${\mathrm{mg}}^{\mathrm{-}1}$ have thus been determined for ${\mathrm{Y}}_3$ ${\mathrm{Fe}}_5$ ${\mathrm{O}}_{12}$ and ${\mathrm{BaFe}}_{12}$ ${\mathrm{O}}_{19}$, respectively. Furthermore, drastic changes in the bulk orientation of the hyperfine magnetic field $H_f$ have been observed in yttrium iron garnet: The $H_f$ distribution is isotropic for Ar irradiations and anisotropic for Xe irradiations, while two types of $H_f$ distributions are observed for Kr irradiations, depending on the values of the deposited energy compared to that of the threshold energy. Comparison with latent-track models is performed.