Investigation of structural, magnetic and dielectric properties of Al-doped samarium iron garnet

Polycrystalline Sm-3(Fe1-xAlx)(5)O-12 (x = 0, 0.1, 0.2, 0.3, 0.4) samples were prepared in single phase form. Rietveld analysis of X-ray diffraction patterns shows that samples crystallize in cubic structure (space group: Ia (3) over bard) with a systematic decrease in lattice constant with Al doping. Magnetization measurements show that all these samples exhibit ferrimagnetic transition whose transition temperature (T-c) decreases from 562 K for x = 0 to 350 K for x = 0.4 due to the dilution of Fe3+-O-Fe3+ networks. In addition to that they undergo spin reorientation transition at T-SR similar to 70 K with considerable magnetic irreversibility below T-SR. Interestingly the x = 0.4 sample undergoes magnetic compensation at 26 K. Improvement of frequency response of dielectric constant (epsilon') and loss tangent (tan delta) is observed upon Al doping in a wide frequency range of 10(2)-10(9) Hz.