Relaxation in the 3D ordered CoTAC spin chain by quantum nucleation of 0D domain walls

TL;DR

This paper demonstrates quantum tunnelling of magnetisation in a 3D ordered CoTAC spin chain, revealing different relaxation behaviors from ZFC and saturated states at a specific resonant field.

Contribution

It provides the first observation of quantum tunnelling in a 3D ordered molecular spin chain, expanding understanding beyond zero-dimensional systems.

Findings

Quantum tunnelling observed in CoTAC spin chain.

Relaxation from ZFC state is exponential.

Relaxation from saturated state is complex.

Abstract

We have shown that resonant quantum tunnelling of the magnetisation (QTM), until now observed only in 0D cluster systems (SMMs), occurs in the molecular Ising spin chain, CoTAC ([(CH_3)_3NH]CoCl_3 - 2H_2O) which orders as a canted 3D-antiferromagnet at T_C=4.15 K. This effect was observed around a resonant like field value of 1025 Oe. We present here measurements of the relaxation of the magnetisation as a function of time, from the zero field cooled (ZFC) antiferromagnet state and from the saturated ferromagnet state. We show that, at the resonant field, the relaxation from the saturated state occurs in a complicated process, whereas, surprisingly, in the case of the ZFC state, the relaxation is exponential.