Quantum Tunneling In A Uniaxial Ferromagnetic Particle In Transverse Magnetic Field

The theoretical and experimental studies on the magnetic macroscopic quantum effects not only can test whether there exists the coherent superposition of schrodinger cat states, i. e. macroscopic quantum states ,which is a challenging problem since quantum mechanics was founded ,but also lead to the potential application in information storage ,quantum computing and quantum information process. It is the main purpose of this paper to calculate the energy splitting of ground state and excited states induced by thermally assisted quantum tunneling .First, a brief introduction is given for the theoretical and experimental studies on the magnetic macroscopic quantum effects .Then, spin tunneling in a uniaxial ferromagnetic particle in transverse magnetic field is converted to a pseudoparticle moving in effective double-well potential with the help of the effective potential description of quantum spin systems developed by Ulyanov and Zaslavskii. Finally using the periodic instanton method we evaluate the transition amplitude, energy shift and prefactor of WKB exponential and The energy splitting of ground state and the tunneling rate for excited states induced by thermally assisted quantum tunneling are obtained.