Analytical study of the spin tunneling effect by considering dipole excitations in single-molecular magnet Mn12

Spin tunneling effect in Single Molecule Magnet Mn12 is studied by instanton calculation technique using SU(2) spin coherent state in real parameter as a trial function. For this SMM, tunnel splitting ( steps in hysteresis loop) arises due to the presence of a Berry phase in action, which causes interference between tunneling trajectories (instantons). In the analytical calculation, the assumption of the linearity of the instanton solution in term of applied magnetic field is used. It is observed that the number of quenching points of magnetic tunneling, the number of steps in hysteresis loop, are equal to the number of points obtained from numerical calculation. Of course, the position of the points (the magnitude of the field in which the tunneling amplitude is zero) is different.