The use of Gev heavy ion beam irradiation has auracted much attention in the field of material science. In the case of garnets, the superexchange inreraction among the maguetie cations in the materials is very sensitive to the electronic stopping power of the beam. The induced microstructure and magnetic propertics of irradiated Ca V Sn: YIG samples have been characterized by means of Mossbauer spectroscopy, high resohution electron microscopy (HREM), X-ray diffraction (XRD), positron annihilation techniques (PAT), vibrating sample magnetometry and ferrimagnetic resonance (FMR). The experimental results are discussed in this paper.