Energy-dependent contrast in atomic-scale spin-polarized scanning tunneling microscopy of Mn3N2 (010): Experiment and first-principles theory

The row-wise antiferromagnetic Mn₃N₂ (010) surface has been investigated using atomic-scale spin-polarized scanning tunneling microscopy. Localizing the experimental image at a particular region of the surface, the bias voltage-dependent behavior and resulting energy-dependent magnetic contrast are investigated. It is found that the magnetic contrast varies strongly over the energy range from E_Fermi-1eV to E_Fermi+1eV , including a magnetic contrast reversal at ∼E_Fermi+0.4eV . Spin-polarized density-functional theory has been combined with the spin-generalized Tersoff-Hamann model to simulate the experimental results on Mn₃N₂ (010). Excellent agreement is found which shows that the observed bias-dependent behavior derives from the properties of the sample surface, not the tunneling tip. The bias-dependent contrast reversal, as well as bias-dependent line profile shape, are both found to result from a transition from majority (d_z²) to minority (d_yz) spin-polarized Mn atomic orbital lobes.