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

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.Comment: 6 pages, Latex, with 1 ps figur