Dielectric characteristics of substituted M-type strontium hexaferrite crystals and their modifications on swift heavy ion irradiation

Dielectric behaviour of flux grown substituted crystals bearing composition SrGaxInyFe12−(x+y)O19 (x = 5, 7, 9; y = 0.8, 1.3, 1.0) is reported. Variation of dielectric constant (ɛ/), dielectric loss (tan δ) and ac conductivity (σac) with temperature in the range 30-500 °C under the frequency of the applied ac field in the range 1-104 kHz for all the varied compositions are analyzed and explained. Swift heavy ion irradiation effects on these parameters are investigated. On irradiation the crystals show changes in the values of dielectric constant (ɛ/), dielectric loss (tan δ) and ac conductivity (σac). The frequency variation of ɛ/ and tan δ is explained by Koop's phenomenological theory and hopping frequency of electrons between Fe2+ and Fe3+ on octahedral sites for both irradiated and unirradiated crystals.