Selection rules for Single-Chain-Magnet behavior in non-collinear Ising systems

TL;DR

This paper extends Glauber dynamics to non-collinear Ising systems to explain Single-Chain Magnet behavior, revealing selection rules for slow relaxation and resonance phenomena in various magnetic chain geometries.

Contribution

It introduces modifications to Glauber theory for non-collinear anisotropy axes and applies it to real molecular magnetic chains, broadening understanding of Single-Chain Magnet behavior.

Findings

Selection rules for slow relaxation at low temperatures.

Resonant behavior of ac susceptibility at low frequencies.

Applicability to Mn-, Dy-, and Co-based chains.

Abstract

The magnetic behavior of molecular Single-Chain Magnets is investigated in the framework of a one-dimensional Ising model with single spin-flip Glauber dynamics. Opportune modifications to the original theory are required in order to account for reciprocal non-collinearity of local anisotropy axes and the crystallographic (laboratory) frame. The extension of Glauber's theory to the case of a collinear Ising ferrimagnetic chain is also discussed. Within this formalism, both the dynamics of magnetization reversal in zero field and the response of the system to a weak magnetic field, oscillating in time, are studied. Depending on the geometry, selection rules are found for the occurrence of slow relaxation of the magnetization at low temperatures, as well as for resonant behavior of the a.c. susceptibility as a function of temperature at low frequencies. The present theory applies successfully to some real systems, namely Mn-, Dy-, and Co-based molecular magnetic chains, showing that Single-Chain-Magnet behavior is not only a feature of collinear ferro- and ferrimagnetic, but also of canted antiferromagnetic chains.