AVS 51st International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoA

Invited Paper NS-MoA3
Atomic-Scale Spin-Polarized Scanning Tunneling Microscopy of Magnetic Transition Metal Nitride Surfaces

Monday, November 15, 2004, 2:40 pm, Room 213D

Session: Magnetic Imaging and Spectroscopy
Presenter: A.R. Smith, Ohio University
Authors: A.R. Smith, Ohio University
R. Yang, Ohio University
H.Q. Yang, Texas A&M University
W.R.L. Lambrecht, Case Western Reserve University
A. Dick, Fritz-Haber-Institut der MPG, Germany
J. Neugebauer, Fritz-Haber-Institut der MPG, Germany
Correspondent: Click to Email
Spin-polarized scanning tunneling microscopy (SP-STM) can achieve ultimate magnetic resolution on surfaces, even down to the atomic scale.@footnote 1@@footnote ,@@footnote 2@@footnote ,@@footnote 3@ In earlier work, we have shown the resolution of the spin structure of a novel antiferromagnetic (aFM) surface, Mn@sub 3@N@sub 2@ (010), with a model row-wise aFM structure.@footnote 3@ The surface is prepared using molecular beam epitaxy with a Mn effusion cell and radio frequency N plasma. The magnetic information appears as an additional component which is added to the non-magnetic component in the STM line scan. Furthermore, the magnetic information is bias-dependent; both the amplitude and polarity of the magnetic profile vary with the STM bias. The bias-dependence is understood as energy-dependent variations of the spin density of states of tip and sample. Both the magnetic and non-magnetic information can be extracted from the total STM image and compared with simulations based on theoretical calculations. Using first principles density functional theory, the local density of states for the surface is calculated for Mn@sub 3@N@sub 2@ (010). Two methods of simulation have been investigated for SP-STM. First, we have applied the atom superposition method (ASM). Second, we have simulated the images using the full Tersoff-Hamann (T-H) approach.@footnote 4@ We find that the T-H method is, in general, necessary for a correct simulation of the data due to the spin-dependent orbital lobes of the surface atoms. We furthermore apply the full T-H theory with different numbers of tip atoms to best model the STM data with good success. @FootnoteText@ @footnote 1@S. Heinze {\it et al.}, Science {\bf 288}, 1805 (2000). @footnote 2@D. Wortmann {\it et al.}, Phys. Rev. Lett. {\bf 86}, 4132 (2001). @footnote 3@H. Yang {\it et al.}, Phys. Rev. Lett. {\bf 89}, 226101 (2002). @footnote 4@J. Tersoff et al., Phys. Rev. Lett 50(25), 1998 (1983).