Design of molecular spin devices: Control of surface spin states

Advent of scanning tunneling microscope (STM) enabled us to observe and manipulate surface atoms by using an STM tip. Some theories for atom observation and manipulation under the STM environment were proposed. However, due to the restriction of calculational methods, spin properties of the whole system including surface atoms, a sample substrates and an STM tip are ignored. We investigate surface electronic states using molecular orbital theory which involves spin states explicitly. Based on the study on the behavior of surface electronic states, we found spin multiplicity of atoms plays an important role to determine the potential energy surfaces of a surface absorbed atoms between an STM tip and a sample. Taking advantage of these peculiar properties, we propose a mechanism for a spin device.