Observation of direct magneto-dielectric behaviour in Lu sub(3)Fe sub(5)O sub(12-) delta above room-temperature

The coupling of dielectric and magnetic order is highly nontrivial and seldom observed in rare-earth iron garnets. Careful investigations on polycrystalline Lu sub(3)Fe sub(5)O sub(12-) delta , prepared by the solid state route, establish a direct correlation between the magnetic and dielectric order parameters. A dielectric anomaly at the magnetic ordering temperature supports this correlation. The dielectric permittivity at various magnetic fields is measured using an indigenously developed connector setup. Lu sub(3)Fe sub(5)O sub(12-) delta exhibits a magneto-dielectric coupling of similar to 6% at room temperature, which is significant in the case of a single-phase magneto-dielectric material at low fields. Rietveld refinement of the X-ray diffraction pattern, bond valence sum method, Mossbauer spectroscopy, and X-ray photoelectron spectroscopy indicate two different oxidation states of Fe. Complete structural optimizations performed using the density functional theory establish a ferrimagnetic ground state and provide structural parameters in agreement with experimental values. Electronic structure analysis shows that Lu sub(3)Fe sub(5)O sub(12) exhibits insulating behavior both in ferromagnetic and ferrimagnetic configurations. The capability of Lu sub(3)Fe sub(5)O sub(12-) delta to exhibit room temperature magneto-dielectric response is a key factor in designing and fabricating various electronic devices and sensors.