Short range ferromagnetic, magneto-electric, and magneto-dielectric effect in ceramic Co3TeO6

Abstract

We report observation of magneto-electric and magneto-dielectric couplings along with short range ferromagnetic order in ceramic Cobalt Tellurate (Co3TeO6, CTO) using magnetic, structural, dielectric, pyroelectric, and polarization studies. DC magnetization along with dielectric constant measurements indicate a coupling between magnetic order and electrical polarization. A strong anomaly in the dielectric constant at ∼17.4 K in zero magnetic field indicates spontaneous electric polarization, consistent with a recent neutron diffraction study. Observation of weak short range ferromagnetic order at lower temperatures is attributed to the Griffiths-like ferromagnetism. Furthermore, magnetic field dependence of the ferroelectric transition follows earlier theoretical predictions, applicable to single crystal CTO. Finally, combined dielectric, pyroelectric, and polarization measurements suggest that the ground state of CTO may possess spontaneous symmetry breaking in the absence of magnetic field.

Insight into the Growth Reaction Mechanism of Ceramic Co3TeO6: Synchrotron Structural and Thermal Analysis

“…On the other hand, comparison of Te L‐edge XANES spectra with their standards clearly indicates Te 6+ oxidation state in CTO. Although, XANES results on Co oxidation states are unambiguous, disagree with published results, and also with chemical formula unit of the CTO sample, which suggests +2 oxidation state of Co, better multiferroic properties have been seen in our ceramic CTO …”

“…Detailed Rietveld refinements provide the insight into the structural investigation of the single‐phasic CTO and the results are in a good agreement with the reported patterns of crushed single‐crystal as well as powder XRD data . All the structural aspects of our monophasic ceramic CTO, Rietveld refinements details and their structural parameters data can be found elsewhere …”

“…Furthermore, XANES study at Co K and Te L edges indicate mixed oxidation states of Co and hexavalent Te in CTO, and the charge neutrality for Co 3 TeO 6 has been established by invoking cations vacancies. It is also interesting to note that the existence of Co 3+ ions in our sample does not diminish any of the multiferroic property reported earlier in polycrystalline as well as in single‐crystal CTO, but enhances some of the observables …”

“…Multiferroics, wherein coupling among various ferroic‐order parameters like electrical polarization (P) and magnetization (M) in the same phase occurs, have attracted great attentions due to their promising application in spintronics, magnetic data storage devices, solar cell, etc . In the quest of the new and better performing materials, cobalt tellurate Co 3 TeO 6 (CTO) seems to have favorable characteristics . The renewed interest in CTO is due to its low‐temperature type II multiferroic property.…”

“…Herein, we report synthesis of the single‐phase CTO using two‐step reactions between Co 3 O 4 and TeO 2 in air, at temperature T < 1100 K, and discuss its growth reaction mechanism. The sample has been found to show better multiferroic properties, which are attributed to the presence of mixed oxidation states of Co ions, specially the high spin state of Co 3+ …”