Quadrupole Excitations in hysteresis loops of magnetic NanoCluster $Fe_8$

TL;DR

This paper investigates the role of both dipole and quadrupole excitations in the quantum resonant tunneling phenomena observed in the hysteresis loops of high-spin nanocluster $Fe_8$, providing a more comprehensive theoretical model.

Contribution

It introduces the consideration of quadrupole excitations alongside dipole excitations in modeling $Fe_8$ nanoclusters, enhancing understanding of tunneling phenomena.

Findings

Quadrupole excitations significantly affect tunneling behavior.

Numerical results show differences between models with and without quadrupole excitations.

The model including quadrupole excitations aligns better with experimental observations.

Abstract

Experiments show several steps in hysteresis loops of high spin nanocluster $Fe_8$. It is thought that these steps are due to thermally assisted resonant tunneling between different quanta spin states. Up to now, in calculatiing it, only dipole excitations were considered. Because of the symmetry and the power of spin operators in Hamiltonian, we think that other multipole excitation must be considered too. In this paper we consider both dipole and quadrupole excitations in Hamiltonian and then quantum resonant tunneling phenomena are obtained numerically. As we can show in these figures, this phenomenon is different in these two conditions and the second condition is nearly to the fact.