Abstract
Here, we report the dielectric, impedance and transport studies of non-charge-ordered magnetic glass, Tb0.5Sr0.5MnO3 single crystals. The temperature- and frequency-dependent real and imaginary ( or tanδ) parts of the dielectric constant display large frequency dispersion. The colossal dielectric constant observed above 100 K is considered extrinsic. The activation energy of thermally activated relaxation is calculated using the Arrhenius law. Interestingly, two relaxation regions, each with different activation energies (Ea) are clearly evident, one occurring above and the other below the glassy magnetic transition temperature . Ea relates to the electron hopping between Mn3+ and Mn4+ ions and the origin of dielectric dispersion. Ea in the glassy region is lower than that in paramagnetic region due to a lower energy spent in hopping between frozen spins. Bulk capacitance and resistivity derived from impedance measurements reveal anomalies around Tg. Electrical transport data between 60 and 300 K shows insulating behavior and the calculated Ea is in good agreement with the value obtained from dielectric measurements. Although, these results cannot be interpreted in terms of magneto-electric coupling, the correlation observed between magnetic and electronic states of the system is significant.
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