We present a theoretical study of the Zeeman relaxation of the magnetically trappable lowest field seeking state of MnH(^7 Sigma) in collisions with 3He. We analyze the collisional Zeeman transition mechanism as a function of the final diatomic state
and its variation as a function of an applied magnetic field. We show that as a result of this mechanism the levels with Delta Mj>2 give negligible contributions to the Zeemam relaxation cross section. We also compare our results to the experimental cross sections obtained from the buffer gas cooling and magnetic trapping of this molecule and investigate the dependence of the Zeeman relaxation cross section on the accuracy of the three body interaction at ultralow energies.
