Structural and magnetic properties of the ordered perovskite Pb2CoTeO6

TL;DR

This study investigates the structural and magnetic properties of Pb2CoTeO6, revealing multiple temperature-induced phase transitions, magnetic ordering at low temperatures, and potential multiferroic behavior in this complex perovskite.

Contribution

The paper provides a detailed analysis of the phase transitions and magnetic structure of Pb2CoTeO6, highlighting its multiferroic potential and structural evolution across a wide temperature range.

Findings

Four distinct structural phases between 5-500 K.

Magnetic ordering observed below 16 K.

Coupled dielectric and heat capacity anomalies at 210 and 370 K.

Abstract

The complex perovskite Pb2CoTeO6 (PCTO) has been prepared as polycrystalline powders by solid state reaction route, and the crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, dielectric, calorimetric and magnetic measurements. It was shown that at room temperature this compound adopts a trigonal perovskite structure, space group R-3 (a= 5.6782(1){\AA}, c= 13.8552(3){\AA}). The compound undergoes a number of temperature-induced phase transitions and adopts four different structures in the temperature range 5-500 K: monoclinic in P21/n(5<T<125K, tilt system (a+b-b-)), monoclinic in I2/m (125<T<210 K, tilt system (a0b-b-)), rhombohedral in R-3 (210<T<370K, tilt system (a-a-a-)), and finally cubic in Fm-3m (above 370K without any tilting). These structural phase transitions are coupled to a change in the dielectric constant and the heat capacity around 210 and 370K. A long-range antiferromagnetically ordered state has been identified from neutron powder diffraction and magnetic studies at different temperatures. Magnetic diffraction peaks were registered below the transition at about 16 K and a possible model for the magnetic structure is proposed. Possible coexistence of long-range ordering of electrical dipoles and magnetic moments at low temperatures making PCTO a multiferroic candidate is discussed and compared with those of other Co-based quaternary oxides adopting the perovskite structure.