We propose a theory for a type of apertureless scanning near field microscopy that is intended to allow the measurement of magnetism on a nanometer length scale. A scanning tunneling microscope (STM) is used to scan a magnetic substrate while a laser is focused on the STM tip. The electric field between the tip and substrate is enhanced in such a way that the magnetic Kerr effect, which is normally of order 0.1%, is increased by up to two orders of magnitude for the case of a Ag or W tip and an Fe sample. Apart from this there is also a large background of circular polarization which is non-magnetic in origin. This circular polarization is produced by light scattered from the STM tip and substrate. A detailed retarded calculation for this light-in-light-out experiment is presented.
Citation: Physical Review B (Condensed Matter and Materials Physics)
Pub Type: Journals
Kerr effect, laser, microscope, nanometer resolution, near field microscopy, STM