With the development of high dense storage for memory cell, more attention was paid to the single molecule magnet (SMM). SMM is a big cluster containing magnetic ions  and , which can exhibit the properties similar both to a nanoscale magnetic particle and quantum characters, e.g. quantum tunneling and quantum coherence. Due to its large uniaxial magnetic anisotropy, the SMM possesses two metastable spin states corresponding to the double well of LDN 57444 potential at low temperature, which can be trapped in one of the two states. Thus, the SMMs seem to be good candidates for future high density memory cells ,  and . A new field of molecular spintronics is emerging, which is an integration of the traditional spintronics and the molecular electronics. It is possible to manipulate the state of SMM by a spin-polarized current. Since the current technology can realize to attach SMM to electronic contacts ,  and , reading and writing information into SMM will be possible in near future.