Glassy Dielectric Response in Tb_2NiMnO_6 Double Perovskite with Similarities to a Griffiths Phase

Abstract

Frequency-dependent and temperature-dependent dielectric measurements are performed on double perovskite Tb${}_2$NiMnO${}_6$. The real (${\epsilon }_1$) and imaginary (${\epsilon }_2$) parts of dielectric permittivity show three plateaus suggesting dielectric relaxation originating from bulk, grain boundaries and the sample-electrode interfaces respectively. The temperature and frequency variation of ${\epsilon }_1$ and ${\epsilon }_2$ are successfully simulated by a $RC$ circuit model. The complex plane of impedance, $Z^{\prime }$-$Z"$, is simulated using a series network with a resistor $R$ and a constant phase element. Through the analysis of frequency-dependent dielectric constant using modified-Debye model, different relaxation regimes are identified. Temperature dependence of dc conductivity also presents a clear change in slope at, $T^{\ast }$. Interestingly, $T^{\ast }$ compares with the temperature at which an anomaly occurs in the phonon modes and the Griffiths temperature for this compound. The components $R$ and $C$ corresponding to the bulk and the parameter $\alpha$ from modified-Debye fit tend support to this hypothesis. Though these results cannot be interpreted as magnetoelectric coupling, the relationship between lattice and magnetism is marked.

Accepted in Europhysics Letters

References in corpus (2)

• Impedance spectroscopy of epitaxial multiferroic thin films
• Absence of long-range Ni/Mn ordering in ferromagnetic La2NiMnO6 thin films

Cited by in corpus (1)

• Ferromagnetism and the Effect of Free Charge Carriers on Electric Polarization in Y_2NiMnO_6 Double Perovskite