Magnetic quantum tunnelling in Fe8 with excited nuclei

TL;DR

This study explores how nuclear spin fluctuations influence quantum tunneling in Fe8, finding that nuclear spin temperature does not affect tunneling probability, highlighting the hyperfine field's role.

Contribution

It demonstrates experimentally that nuclear spin temperature has no impact on quantum tunneling in Fe8, emphasizing the hyperfine field's significance, supported by theoretical explanation.

Findings

Nuclear spin temperature does not affect tunneling probability.

Nuclear spin-spin relaxation time T2 depends strongly on temperature.

Hyperfine field strength is the key factor in quantum tunneling.

Abstract

We investigate the effect of dynamic nuclear spin fluctuation on quantum tunneling of the magnetization (QTM) in the molecular magnet Fe8 by increasing the nuclei temperature using radio frequency (RF) pulses before the hysteresis loop measurements. The RF pulses do not change the electrons spin temperature. Independently we show that the nuclear spin-spin relaxation time T2 has strong temperature dependence. Nevertheless, we found no effect of the nuclear spin temperature on the tunneling probability. This suggests that in our experimental conditions only the hyperfine field strength is relevant for QTM. We demonstrate theoretically how this can occur.