Application of spin-dynamics methods to a study of magnetization tunnelingin many-spin systems

Spin-dynamics methods were applied for the numerical study of magnetic tunn eling in many-spin systems. A numerical technique based on the instanton ap proach was developed and the zero-temperature case as well as finite-temper ature effects were considered. We show that even for a two-spin system resu lts can differ considerably from those of a corresponding reduced one-spin (or collective spin) system. Moreover, it is argued that such a difference can take place for real materials such as magnetic molecules (e.g., Mn-12). Thus, consideration of the many-spin nature of some systems is shown to be important. (C) 1998 American Institute of Physics.