Abstract
Spin-polarized STM (SP-STM) is a powerful tool to visualize sample spin-polarization vectors at an atomic scale. A difficulty of SP-STM measurement is how to fabricate a tip with a stable spin-polarization vector. In 1990's, first, many efforts were payed for a GaAs tip with optically pumping, but finally 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 film 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.
