Tunnel splitting in biaxial spin particles as a function of applied magnetic field

Abstract

The tunneling splitting in biaxial ferromagnetic particles is investigated as a function of magnetic field applied along an arbitrary direction in the plane of hard and medium axes. We use a potential field description of spin systems with exact spin-coordinate correspondence which is suitable for quantum tunneling in molecular clusters. The quantum phase interference induced by the Zeeman energy with the magnetic field along the hard axis results in the oscillation of tunnel splitting. The oscillation is gradually smeared when the direction of the magnetic field tends to the medium axis. Our results agree perfectly with the numerical calculation by performing a diagonalization of the Hamilton operator of the spin system and explains qualitatively the recent experimental observation with the ${\mathrm{Fe}}_{8}$ molecular cluster.