Dielectric and impedance spectroscopy of Nd₂CoIrO₆ double perovskite

Abstract

Polycrystalline Nd 2 CoIrO 6 double perovskite crystallizes in monoclinic crystal structure with P2 1 /n space group. The average grain size of powder sample is 400-500 nm. The dielectric, impedance and ac conductivity of the sample were studied in the temperature range 5-300 K and in the frequency range 20 Hz-2 MHz. Dielectric constant reveals a step like increase from low temperature value of ∼5 to colossal value of ∼10 4 at high temperature. High value of dielectric constant is associated with Maxwell-Wagner polarization due to large grain boundary capacitance. Cations (Co 2+ and Ir 4+ ) disorder leads to variable range hopping conduction of electrons in grain and grain boundary regions. Distribution of grain size induces distribution of relaxation time as confirmed from depressed semicircles in Nyquist plots. Frequency dependent conductivity follows universal power law behavior.

Maxwell–Wagner Polarization and Mixed Ferromagnetic and Antiferromagnetic State in Eu2CoMnO6

“…[ 64 ] The complex impedance study has also been employed to compare the microstructural contribution to the electrical properties of the materials, using an electrical equivalent circuit ascribed to intergranular/grain‐boundary resistance and capacitance. [ 62,65,66 ] The semicircular‐type arc of Cole–Cole plots intercepts almost at the origin (which can be clearly observed from the inset of Figure 6) confirming the absence of contact resistance. Moreover, this arc also intercepts at a higher value of Z ′ (which is marked with green arrows), suggesting that the observed MW dielectric relaxation in ECMO is predominantly owing to grain‐boundary contribution.…”

“…As discussed, the dielectric relaxation in ECMO is attributed to non-Debye/MW polarization where the materials do not passes any permanent dipole moment. [62] The electric polarization arises owing to interfacial depletion layers of carrier among sample and contact and at the grain boundaries. [55,57,58] The frequency-dependent properties of complicated oxides are generally analyzed using complex functions such as impedance (Z ) study.…”

“…[55,57,58] The frequency-dependent properties of complicated oxides are generally analyzed using complex functions such as impedance (Z ) study. [62,63] Figure 6 shows the Cole-Cole plot (Z 0 vs. Z 00 ) of ECMO at different temperatures. This figure shows the presence of a semicircular-type arc.…”

Multifunctional behaviour in B-site disordered double perovskite EuPrCoMnO6

“…The heterogeneity increases the probability of inter-well hopping which affects dielectric relaxation mostly at lower frequency and owing to the heterogeneous distribution charge carriers pileup which response in a different way to the external electric field [64]. These dielectric relaxations are mainly described by non-Debye/Maxwell-Wagner (MW) interfacial polarization where the system does not have a permanent dipole moment [65].…”

A combined study on structural, magnetic and specific heat on double perovskite iridates Ln2CoIrO6 [Ln = Pr, Nd]

“…Here, we study the magnetic ground state of Pr 2 CoIrO 6 (PCIO) and Nd 2 CoIrO 6 (NCIO) where the DP iridates have an intermediate magnetic A-site cation (µ Pr 3+ = 3.58 µ B and µ Nd 3+ = 3.62 µ B ) [18]. Nd 2 CoIrO 6 have been reported recently to shows a high value of dielectric constant (∼10 4 ) and this high value of dielectric constant is related to Maxwell-Wagner polarization [19].…”