Anomalous ferromagnetic behavior in the orthorhombic Li$_3$Co$_2$SbO$_6$

TL;DR

This study investigates the magnetic properties of orthorhombic Li$_3$Co$_2$SbO$_6$, revealing complex magnetic transitions and anomalous ferromagnetic behavior likely caused by stacking faults and local disorders.

Contribution

It provides the first detailed magnetic characterization of the orthorhombic phase, highlighting its anomalous ferromagnetic behavior and the effects of structural disorders.

Findings

Multiple magnetic transitions at 115, 89, and 71 K observed.

Long-range magnetic order confirmed at 115 K.

Discrepancies in transition temperatures attributed to stacking faults.

Abstract

Monoclinic Li$_3$Co$_2$SbO$_6$ has been proposed as a Kitaev spin liquid candidate and investigated intensively, whereas the properties of its polymorph, the orthorhombic phase, is less known. Here we report the magnetic properties of the orthorhombic Li$_3$Co$_2$SbO$_6$ as revealed by dc and ac magnetic susceptibility, muon spin relaxation ($\mu$SR) and neutron diffraction measurements. Successive magnetic transitions at (115, 89 and 71) K were observed in the low field dc susceptibility measurements. The transitions below $T_N$ (= 115 K), are suppressed in higher applied fields. However, zero field, ac susceptibility measurements reveals distinct frequency independent transitions at about (114, 107, 97, 79 and 71) K. A long range magnetic ordered state was confirmed by specific heat, $\mu$SR and neutron diffraction measurements, all indicating a single transition at about 115 K. The discrepancy between different measurements is attributed to possible stacking faults and/or local disorders of the ferromagnetic zig-zag chains, resulting in ferromagnetic boundaries within the overall antiferromagnetic matrix.