Spin-Polarized STM Overview and Issues for Next Developments

Spinpolarized STM (SPSTM) is a powerful tool to visualize sample spinpolarization vectors at an atomic scale. A di‹culty of SPSTM measurement is how to fabricate a tip with a stable spinpolarization vector. In 1990's, ˆrst, many eŠorts were payed for a GaAs tip with optically pumping, but ˆnally the GaAs tip did not detect sample spin polarization due to quenching of the spinpolarization at the GaAs tip apex. However, in 2000, a W tip coated by a magnetic thin ˆlm detected the spinpolarized tunneling current, and spin polarization images of magnetic atoms were successfully obtained. In 2016, more than 15 groups in the world can perform SP STM measurements. History and issues for further development of SPSTM measurements are discussed.