An Extended Effective Potential Method with Topological Phase of Spin Tunnelling

An extended effective potential(EEP)method is proposed to calculate the spin tunnelling splitting of a single domain ferromagnetic grain.By adding a phase factor to replace the boundary conditioin,the new method is not only accurate but also topological effects.In the large spin limit,the results from the spin-coherent-state path integral have systematic disparity with numerical studies,while those from the EEP method agree well with numerical studies.