Observing Spin Polarization of Individual Magnetic Adatoms

Yayon, Y.; Brar, Victor W.; Senapati, L.; Erwin, Steven C.; Crommie, Michael F.

doi:10.1103/physrevlett.99.067202

Cited by 80 publications

(62 citation statements)

References 26 publications

(26 reference statements)

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“…Parallel (P) and antiparallel (AP) tip magnetization directions are set relative to the underneath surface Cr atom. It can clearly be seen that measuring the spectra with oppositely magnetized tips of the same type result in different differential conductance curves, in agreement with SP-STS experiments performed on oppositely magnetized sample areas with a fixed tip magnetization direction [73,75]. For the flat magnetic tip, two different vacuum decays, κ(E) and κ(E, V ) are assumed using Eqs.…”

Section: Di/dv Contributionssupporting

confidence: 48%

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Three-dimensional Wentzel-Kramers-Brillouin approach for the simulation of scanning tunneling microscopy and spectroscopy

2013

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We review the recently developed three-dimensional (3D) atom-superposition approach for simulating scanning tunneling microscopy (STM) and spectroscopy (STS) based on ab initio electronic structure data. In the method, contributions from individual electron tunneling transitions between the tip apex atom and each of the sample surface atoms are summed up assuming the one-dimensional (1D) Wentzel-Kramers-Brillouin (WKB) approximation in all these transitions. This 3D WKB tunneling model is extremely suitable to simulate spin-polarized STM and STS on surfaces exhibiting a complex noncollinear magnetic structure, i.e., without a global spin quantization axis, at very low computational cost. The tip electronic structure from first principles can also be incorporated into the model, that is often assumed to be constant in energy in the vast majority of the related literature, which could lead to a misinterpretation of experimental findings. Using this approach, we highlight some of the electron tunneling features on a prototype frustrated hexagonal antiferromagnetic Cr monolayer on Ag(111) surface. We obtain useful theoretical insights into the simulated quantities that is expected to help the correct evaluation of experimental results. By extending the method to incorporate a simple orbital dependent electron tunneling transmission, we reinvestigate the bias voltage-and tip-dependent contrast inversion effect on the W(110) surface. STM images calculated using this orbital dependent model agree reasonably well with Tersoff-Hamann and Bardeen results. The computational efficiency of the model is remarkable as the k-point samplings of the surface and tip Brillouin zones do not affect the computational time, in contrast to the Bardeen method. In a certain case we obtain a relative computational time gain of 8500 compared to the Bardeen calculation, without the loss of quality. We discuss the advantages and limitations of the 3D WKB method, and show further ways to improve and extend it.

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Section: Di/dv Contributionssupporting

confidence: 48%

“…SP-STS has recently been used to find inversion of spin polarization above magnetic adatoms [73][74][75], and the effect has been explained theoretically [76]. Furthermore, SP-STS is useful to study atomic magnetism [77], magnetic interactions between adatoms [78], and magnetic nanostructures on surfaces, see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional Wentzel-Kramers-Brillouin approach for the simulation of scanning tunneling microscopy and spectroscopy

2013

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“…19,27 With the experimental techniques now available, nanowires and nanostructures may be deposited on magnetic and nonmagnetic surfaces in a controlled fashion, and their fundamental magnetic properties can be explored with the use of advanced experimental methods. [28][29][30][31][32][33][34] From the above discussions, it is quite evident that the magnetic interactions at the interface between Mn and Fe have a very rich variety depending on the geometry and local environment. Particularly, the study of the nanostructures of Mn supported on Fe is quite fascinating.…”

Section: Introductionmentioning

confidence: 99%

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

et al. 2012

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The magnetic properties of Mn nanostructures on the Fe(001) surface have been studied using the noncollinear first-principles real space-linear muffin-tin orbital-atomic sphere approximation method within density-functional theory. We have considered a variety of nanostructures such as adsorbed wires, pyramids, and flat and intermixed clusters of sizes varying from two to nine atoms. Our calculations of interatomic exchange interactions reveal the long-range nature of exchange interactions between Mn-Mn and Mn-Fe atoms. We have found that the strong dependence of these interactions on the local environment, the magnetic frustration, and the effect of spin-orbit coupling lead to the possibility of realizing complex noncollinear magnetic structures such as helical spin spiral and half-skyrmion.

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“…These nanoislands constitute a reference system that has been extensively investigated by Scanning Tunneling Microscopy/Spectroscopy (STM/STS) [10,11,12,13,14]. By acquiring STS data over islands of increasing size, we establish that the occupied surface states exhibit a size-dependent energy shift, i. e. that the d-like band shifts in energy.…”

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confidence: 99%

Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

et al. 2007

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Low-temperature scanning tunneling spectroscopy over Co nanoislands on Cu(111) showed that the surface states of the islands vary with their size. Occupied states exhibit a sizeable downward energy shift as the island size decreases. The position of the occupied states also significantly changes across the islands. Atomic-scale simulations and ab inito calculations demonstrate that the driving force for the observed shift is related to size-dependent mesoscopic relaxations in the nanoislands.PACS numbers: 73.20.At, It was recognized quite early that metallic particles exhibit unique properties that differ significantly from their bulk counterparts [1]. Nanoislands grown on metal surfaces, in particular, have been a matter of intense research for decades in view of prospective applications in a vast variety of domains ranging from magnetoelectronics, catalysis, optoelectronics, to data storage technology. The electronic, magnetic and chemical properties of a nanoisland are governed by the size, shape and structure of the island. These, in turn, are profoundly influenced by the lattice mismatch with the metal substrate and, for heteroepitaxial systems, also by the bonding interactions in the island/substrate interface (ligand effects). Metal islands tend to adopt the lattice parameter of the underlying surface [2], and as a consequence the bond lengths between the metal atoms in the supported nanoisland are different than those in the parent metals, resulting in changes due to strain. A theoretical study on homoepitaxial double layer Cu islands on Cu(111) [3], has shown that the strain produces an inhomogeneous distribution of bond lengths over the nanoisland, the average bond length varying with island size. The nanoislands also locally distort the surface and induce a displacement pattern in the substrate which affects the diffusion of atoms and, ultimately, the growth of the nanoislands.Despite these studies, our knowledge of how strain affects the properties of a metallic nanoisland, especially the electronic states, remains very limited. The fundamental problem of the change in energy upon lattice distortion in solids has first been addressed by J. Friedel within a simple model [4], and latter on extended to various problems of lattice contractions at metal surfaces and clusters [5]. On the same lines, it has been shown for thin films that strain effects, along with ligand effects, can cause a shift of the surface d band [6,7,8], resulting in chemical properties that are significantly different from those of the pure overlayer metal. Recently, a modification of electronic states due to a local strain field induced by a nanopattern formation has been observed for Cu(100) covered with N atoms [9].In this Letter, we specifically focus on the interplay between strain-induced structural relaxations and the surface states of Co nanoislands on Cu(111). These nanoislands constitute a reference system that has been extensively investigated by Scanning Tunneling Microscopy/Spectroscopy (STM/STS) [10,11,12,13,14]. By ...

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Observing Spin Polarization of Individual Magnetic Adatoms

Cited by 80 publications

References 26 publications

Three-dimensional Wentzel-Kramers-Brillouin approach for the simulation of scanning tunneling microscopy and spectroscopy

Three-dimensional Wentzel-Kramers-Brillouin approach for the simulation of scanning tunneling microscopy and spectroscopy

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

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