Low-Temperature Raman, High Magnetic Field Fe-57 Mossbauer, And X-Ray Diffraction Study Of Magnetodielectric Coupling In Polycrystalline Gdfeo3

The present work reports the magnetodielectric (MD), ferroelectric, magnetoelectric (ME), low-temperature (LT) Raman, low-temperature high magnetic field (LTHM) Fe-57 Mossbauer and x-ray diffraction (XRD) studies of polycrystalline multiferroic GdFeO3. Ferroelectric ordering as a result of magnetic ordering of Gd3+ ions (T-N,T-Gd) is confirmed from the pyrocurrent measurements carried out in conventional and bias-electric field protocols. Coupling between magnetic and electric orderings, viz., magneto-electric (ME) coupling, is confirmed by measuring the dielectric constant and pyrocurrent in the presence of magnetic field. A huge magnetodielectric (MD) coefficient (approximate to-12%) is observed below the Gd3+ ordering temperature, reaching a saturation value with a field of about 3 Tesla. From LT Raman data across T-N,T-Gd, the presence of spin-phonon coupling and the development of new modes indicating the symmetry reduction are observed. The average displacement of cations obtained from LTHM XRD measurement corroborates the ferroelectric polarization measurements. Signatures of a transferred hyperfine field are observed from LTHM Fe-57 Mossbauer data. The variation of the effective internal magnetic field obtained from in-field Mossbauer data gives evidence for the predicted spin structures of GdFeO3 with magnetic fields below T-N,T-Gd. The observed anomalous variation of the center shift and resonance area from Fe-57 Mossbauer data across T-N,T-Gd ordering is explained in terms of phonon mode softening. Observed MD and ME effects are explained in terms of spin-phonon coupling as evidenced from LTHM Fe-57 Mossbauer and LT Raman data.