Observation of an unusual equilibrium in the molecular nano-magnet Fe_8

TL;DR

This study observes an unusual low-temperature equilibrium in the Fe_8 molecular nano-magnet, revealing complex relaxation behavior and a competition between quantum tunneling and thermodynamics, with high residual entropy.

Contribution

It reports the first observation of an unusual equilibrium in Fe_8 nano-magnet at sub-Kelvin temperatures and explores the interplay of quantum and thermodynamic effects.

Findings

Unusual equilibrium observed below 900 mK in Fe_8

Relaxation dynamics indicate non-trivial approach to equilibrium

High residual entropy persists at very low temperatures

Abstract

Magnetization measurements made in small fields as a function of temperature reveal an unusual equilibrium below 900 mK for the molecular nano-magnet Fe_8. Measurements of the relaxation of the magnetization demonstrate that the approach to the equilibrium is non-trivial and suggest that a competition exists between quantum tunneling of the giant spins and thermodynamic behavior. As a result, at very low temperature the entropy of the spin system remains very large.