Dielectric properties of α-Fe1.6Ga0.4O3 oxide: A promising magneto-electric material

• Dielectric properties of α-Fe1.6Ga0.4O3 system studied.
• The mechanism of electrical charge relaxation dynamics understood.
• Observation of unusual metal like conductivity in the samples.
• Estimation of electrical contribution from grains and grain boundaries.
• Correlation between dielectric properties and magnetic spins order.

We prepared the samples of α-Fe1.6Ga0.4O3 by mechanical alloying of α-Fe2O3 and β-Ga2O3 and subsequent vacuum annealing. The electrical conductivity and dielectric constant in Ga doped hematite samples is enhanced with respect to α-Fe2O3. In this work, we present dielectric properties of the Ga doped system by recording the frequency dependent electrical conductivity, impedance, modulus, dielectric constant, and phase shift in a wide temperature range. We observed electrical contribution from grain part is more conductive and capacitive in comparison to the grain boundary contribution of the samples. Temperature variation of the dielectric parameters has shown transformation of the conductivity states (semiconductor ↔ metal like ↔ semiconductor) in the samples. The conductivity and dielectric constant curves have shown an anomalous peak at about 300 K for all the samples. Dielectric loss curves indicated coexistence of conduction process and dielectric relaxation process in the samples. The temperature dependence of phase shift shows that conductive effect dominates above 400 K, where as capacitive effects dominate below 400 K. It appeared that dielectric properties below 400 K are correlated with the change of magnetic spins order from canted ferromagnetic to weak antiferromagnetic state in the samples. The studied system is a new class of material where magnetic spin order affects the dielectric properties. The results could be useful for understanding the properties in non-traditional magneto-electric systems.

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