Structural, magnetic and Mossbauer studies of TI doped Gd2Fe17−xTix and Gd2Fe16Ga1−xTix (0≤x≤1)

Abstract

Magnetic compounds of the type Gd2Fe17−xTix and Gd2Fe16Ga1−xTix (x=0.0–1.0) were prepared by arc melting and their structural and magnetic properties were studied by X-ray diffraction (XRD), magnetometery and Mossbauer spectroscopy. The Rietveld analysis of X-ray data shows that these α-Fe free solid-solutions crystallize with Th2Ni17-type structure as main phase along with GdFe2 and TiFe2 as additional phases at higher, x≥0.5 contents. The unit cell volume expands with Ga and Ti content. The Rietveld analysis indicate that both Ti and Ga atoms prefer 12j and 12k sites in both compounds. The effect of Ti and co-substituted Ga–Ti on the bond length are quite different. The saturation magnetization Ms, at 300K for Gd2Fe17−xTix and Gd2Fe16Ga1−xTix was found to decrease linearly with increasing Ti content. The Ms in both compounds at x=1 reduced by 9% as compared to their parent compounds at x=0. The Curie temperature, Tc, for Gd2Fe17−xTix increased from 513K (x=0) to 544K (x=1) while Tc for Gd2Fe16Ga1−xTix reduced from 560 (x=0) to 544K (x=1) with increase in Ti content. Thus the observed variation in Tc follows Gd2Fe17<Gd2Fe16Ti<Gd2Fe16Ga. The observed changes in Tc with Ti substitution may result from the variation in the unit cell volume of compounds which has direct effect on the strength of Fe–Fe exchange-interaction. The Mossbauer results indicate decrease in hyperfine fields and increase in the isomer shifts with the increase in Ti content. Overall co-substituted Ga–Ti, Gd2Fe16Ga1−xTix show high Tc with marginal decline in saturation magnetization. Thus α-Fe free Gd2Fe16Ga1−xTix compounds can be potential candidate for high temperature permanent magnet industrial applications.