Aspects of spin-polarized scanning tunneling microscopy at the atomic scale: experiment, theory, and simulation

The principle and method of atomic-scale spin-polarized scanning tunneling microscopy is discussed, and its application to the case of the (0 1 0) surface of η-phase Mn3N2 is presented. For this surface, new proofs of the spin-polarized effect are presented, and it is also shown that the spin-polarized effect can turn on and off with small changes to the tip apex which can occur during scanning; this indicates that the tip magnetic density of states can and does change at certain points during the experiment. It is also shown how to model height profile data using spin-polarized local density of states of the sample. As well, it is shown how to relate the equation for the total spin-polarized height profile to those of the separated magnetic and non-magnetic height profiles. Comparison of the experimental height profiles to the simulated height profiles based on spin-polarized local densities of states calculated from first-principles density functional theory is shown. In particular, a comparison is made between the results of using the atom-superposition method vs. a full Tersoff–Hamman simulation method. For the case of the transition metal nitride system here, it is shown that the latter method is crucial for a full understanding due to the directionality of the atomic orbital lobes.