Single Atom Magnetometry

Movie: The method of spin-resolved scanning tunnelling spectroscopy can as well be applied to paramagnetic systems, as e.g. single atomic spins. If this is done with an antiferromagnetic tip as a function of an external magnetic field B, the magnetization curve of this individual atomic spin, a so called single-atom magnetization curve (SAM) can be recorded [1]. This is done in the following way. A spin-resolved image of an area with the atomic spins to be investigated is recorded at a magnetic field of Bstart. Then, the tip is retracted and B is changed to the next value. The tip is approached and the next spin-resolved image of the same area is recorded. This is continued until the magnetic field has reached the end value Bend.

As an example, the movie shows a sequence of spin-resolved images of an area with two individual Fe atoms, two pairs of Fe atoms, a three-atom, a four-atom, and a five-atom chain of Fe atoms adsorbed on the Cu(111) surface. Acquisition of each individual spin-resolved image (I = 600 pA, V = -10mV, Vmod = 5mV) of the sequence took 20 minutes. Each image was recorded at the magnetic field value B indicated on the top left corner, which has been incrementally ramped from Bstart = 1:5T to Bend = -1:5T, and back. [2].