Structural, magnetic, and dielectric studies on Gd_0.7Y_0.3MnO₃

Structural, magnetic, specific heat, and dielectric studies were carried out on Y substituted (30 at. %) GdMnO3 compound as a function of temperature. Anomalies occur at ∼41 and 18 K, in the specific heat measurements and are ascribed to paramagnetic, to sinusoidal incommensurate antiferromagnetic transition (ICAFM) and ICAFM to commensurate antiferromagnetic transitions, respectively. Changes in the lattice parameters across these temperatures indicate magneto-elastic coupling present in the compound. However, in the dielectric measurements, an anomaly at 18 K alone is observed and is ascribed to a ferroelectric transition, giving rise to spontaneous ferroelectric ordering at low temperatures. This observation is supported by an anomaly in lattice parameters, across the transition temperature. From the frequency dependent dielectric studies, a strong coupling between Gd3+ and Mn3+ magnetic sublattices is inferred and Y substitution results in substantial changes in the relaxation process compared to that of GdMnO3