Spin-Polarized Scanning Tunneling Spectroscopy of Diluted Magnetic Semiconductor Quantum Dots

Abstract

We have formed ultrathin films of cobalt-doped ZnO quantum dots (QDs), aligned their magnetic domains, and recorded spin-polarized scanning tunneling spectroscopy (SP-STS) with a nickel tip whose magnetization vector was also aligned. From the SP-STS, we have calculated normalized density of states (NDOS) of the diluted magnetic semiconductor (DMS) QDs. We have observed that the intensity of peaks in NDOS spectra has depended on the mutual orientation of the magnetization vectors of the tip of the scanning tunneling microscope (STM) and the domains of the QDs. A higher intensity in the NDOS spectrum is observed in tip–QD systems having their domains aligned parallel to each other as compared to their antiparallel configuration. We have performed a range of control experiments to validate the observation. We hence infer that the orientation of the magnetization vector or the magnetic state of ferromagnetic QDs relative to that of the tip of a STM can be read or probed by recording SP-STS.