Quantum Tunneling in Ferrimagnetic Nanoparticles Coupled to a Spin Bath: An Effective Hamiltonian

TL;DR

This paper develops an effective Hamiltonian model to analyze quantum tunneling in ferrimagnetic nanoparticles interacting with environmental spins, considering different magnetic regimes and validating results with exact diagonalization.

Contribution

It introduces a new effective Hamiltonian that accounts for environmental spin interactions in ferrimagnetic nanoparticles, covering both antiferromagnetic and ferromagnetic tunneling regimes.

Findings

Derived criteria for regime transition.

Validated analytic results with exact diagonalization.

Analyzed tunneling behavior in different magnetic regimes.

Abstract

An effective Hamiltonian, describing quantum tunneling in ferrimagnetic nanoparticles which includes interactions between the electronic spins of nanoparticle and microscopic environmental spins (like nuclear spins or paramagnetic impurities), is obtained. Two limiting cases, describing tunneling in antiferromagnetic and ferromagnetic regimes are considered, and criterion for the transition between the two regimes is found. The validity of analytic results is verified by the exact diagonalization method.