Dielectric Properties of Rare Earth Cobaltates, LnCoO₃ (Ln ═ La, Pr, Nd), Across the Spin-State Transition

Abstract

Dielectric properties of the rare earth cobaltates, LnCoO₃ (Ln = La, Pr and Gd), have been measured over the 85–300 K range at different frequencies. The dielectric constants increase markedly across the low-spin to intermediate-spin state transitions of the Co³⁺ ions. The temperature variation of the loss-tangent data as well as the vibrational spectra suggests the role of coupling of the Jahn-Teller distortion of the intermediate-spin state to the phonons and hence the dielectric relaxation. The dielectric behavior of the cobaltates is in many ways comparable to those of relaxor ferroelectrics.

Keywords:

• Cobaltates
• spin-state transition
• dielectric constant
• Jahn-Teller distortion
• vibrational spectra