Resonant quantum tunneling of spin chains in a three-dimensionnal magnetically ordered state

TL;DR

This paper demonstrates the occurrence of resonant quantum tunneling of magnetization in a 3D-ordered molecular Ising spin chain, revealing quantum effects in a system previously observed only in zero-dimensional clusters.

Contribution

It provides the first evidence of resonant quantum tunneling in a 3D-ordered spin chain system, expanding understanding of quantum phenomena in magnetic materials.

Findings

Resonant quantum tunneling observed below 0.3 K.

Magnetization relaxation is temperature independent.

Magnetization increases when crossing a specific magnetic field.

Abstract

We show that resonant quantum tunneling of the magnetization, until now observed only in zero-dimensional (0D) cluster systems, occurs in the molecular Ising spin chain $[(CH_3)_3NH]CoCl_3\cdot 2H_2O$, which orders as a canted 3D-antiferromagnet at $T_C=4.15 K$. We present three features that prove unambigously the existence of resonant quantum tunneling below $0.3 K$ ($T_C/12$): Temperature independent relaxation of the magnetization, speeding up of the relaxation at a well defined field ($1025 Oe$) and increase of the magnetization each time this field is crossed during a succession of minor hysteresis loops. A mechanism is proposed to describe the behavior based on a simple model of 0D domain wall nucleation.