Electronic picture of spin-polarized tunneling with a Cr tip

Abstract We use spin-resolved scanning tunneling spectroscopy with a Cr-covered W-tip to investigate the magnetic switching of single Co islands on Cu ( 1 1 1 ) in polar magnetic fields. The observed hysteretic curve resembles a shape which is well known from so-called butterfly curves of tunneling magnetoresistance measurements. This indicates that not only the Co-island but also the Cr-tip changes its spin orientation in response to the applied magnetic field. For the interpretation of the experimental observations, we perform ab initio calculations by means of the Korringa–Kohn–Rostoker Green's function method. The calculations demonstrate that the Cr-tip is not a perfect antiferromagnet and has an uncompensated magnetic moment which changes its spin orientation continuously due to the applied magnetic field.