Physical properties in nano-crystalline Ho$_2$CoMnO$_6$

TL;DR

This study investigates the structural, magnetic, vibrational, and dielectric properties of nano-crystalline Ho$_2$CoMnO$_6$, revealing its phase transition, spin-phonon coupling, and conduction mechanisms, contributing to understanding 3d-based double perovskites.

Contribution

First detailed analysis of nano-crystalline Ho$_2$CoMnO$_6$ including structural, magnetic, Raman, and dielectric properties, highlighting spin-phonon coupling and conduction behavior.

Findings

Crystallizes in monoclinic P2$_1$/n phase

Undergoes paramagnetic to ferromagnetic transition at ~85 K

Exhibits spin-phonon coupling and non-ideal dielectric behavior

Abstract

3$d$ based double perovskite materials have received much attention in recent years due to their exotic magnetic structure and magneto-electric coupling. In this work we have prepared and studied the nano-crystalline sample of Ho$_2$CoMnO$_6$. Structural, magnetic, Raman and dielectric properties have been studied in detail. The structural analysis shows that the sample crystallize in monoclanic crystal structure with $\textit{P2$_1$/n}$ phase group. The X-ray photoelectron spectroscopy have been employed to confirms the charge state of cations presents in the material. Magnetic study shows that the sample undergoes a paramagnetic to ferromagnetic phase transition around $T_c$ $\sim$85 K. The isothermal magnetization measurements shows hysteresis curve hence confirm ferromagnetic behavior at low temperature. Temperature dependent Raman study reveals that there is spin phonon coupling in the sample marked by deviation in phonon mode from anharmonic behavior. Dielectric response of Ho$_2$CoMnO$_6$ shows the large dispersion and large dielectric constant. Impedance spectroscopy and electrical modulus study reveal that system shows deviation from ideal Debye model. AC conductivity have been studied as a function of both temperature and frequency. We found that the conduction mechanism is obeyed by Jonscher's model. The exponent factor $n$ is suggest that the material deviates from ideal Debye model.