Structural and magnetic anomalies among the spin-chain compounds, Ca3Co1+xIr1-xO6

TL;DR

This study investigates the structural and magnetic properties of Ca3Co1+xIr1-xO6 spin-chain oxides, revealing composition-dependent crystal symmetry changes and spin-glass behavior with significant frequency-dependent anomalies below 50 K.

Contribution

It reports the first detailed analysis of structural distortions and magnetic anomalies in Ca3Co1+xIr1-xO6 compounds, highlighting the sensitivity of magnetic interactions to crystallographic changes.

Findings

Different compositions exhibit distinct crystal structures, including rhombohedral and monoclinic forms.

All compositions show spin-glass behavior with large frequency dependence in ac susceptibility.

The magnetic coupling sign changes with composition, linked to structural distortions.

Abstract

The results of x-ray diffraction, and ac and dc magnetization as a function of temperature are reported for a new class of spin-chain oxides, Ca3Co1+xIr1-xO6. While the x= 0.0, 0.3, 0.5 and 1.0 are found to form in the K4CdCl6-derived rhombhohedral (space group R-3c) structure, the x= 0.7 composition is found to undergo a monoclinic distortion in contrast to a literature report. Apparently, the change in the crystal symmetry with x manifests itself as a change in the sign of paramagnetic Curie temperature for this composition as though magnetic coupling sensitively depends on such crystallographic distortions. All the compositions exhibit spin-glass anomalies with an unusually large frequency dependence of the peak temperature in ac susceptibility in a temperature range below 50 K, interestingly obeying Voger-Fulcher relationship even for the stoichiometric compounds.