Abstract
? 2022 Elsevier B.V.A combined technique of mechanical alloying and heat treatment has been used to prepare the polycrystalline samples of Fe2?xGaxO3 (x = 0.6–1.2) system in orthorhombic phase. It has been possible to reduce the sintering temperature by ~350 °C for stabilizing the orthorhombic phase in comparison to the temperature reported in literature. The Rietveld refinement of X-ray diffraction patterns indicated the distribution of Ga and Fe atoms in the Ga1, Ga2, Fe1 and Fe2 sites of the lattice structure. A linear variation of the lattice parameters with Ga/Fe content showed application of Vegard's law. The temperature-dependent magnetization measurements confirmed ferrimagnetic order of Fe spin moments. The ferrimagnetic transition temperature (TC) has decreased from 320 K to 100 K with the increase of Ga content in the range of x = 0.6–1.2. Temperature-dependent Raman spectroscopy data ruled out any structural phase transition at TC, but an anomalous behaviour of the position and width of the peaks of Raman active phonon modes near to TC confirmed a strong spin–phonon coupling in the material. The spin–phonon coupling strength (η) for the A9 mode has been found around 1.64 cm?1 for x = 1 and 3.34 cm?1 for x = 0.8, and η for the A21 mode has been found around 2.12 cm?1 for x = 1 and 3.28 cm?1 for x = 0.8. The spin-phonon coupling strength has been diluted in the samples with higher content of Ga. The experimental results indicated that the variation of Ga/Fe content and its distribution in lattice sites determine the ferrimagnetic properties, magnetic anisotropy and spin-phonon coupling in Fe2?xGaxO3 system. The results are expected to be useful for understanding the spin-phonon coupling in multiferroic-magnetoelectric materials with magnetic and electric transitions near to room temperature.
NSTL
Elsevier