arXiv subjects

Giancarlo Panaccione

Publications and source records attributed to Giancarlo Panaccione.

23 records · Page 2Linked to original sources

arXiv2014

Observation of Distinct Bulk and Surface Chemical Environments in a Topological Insulator under Magnetic doping

The influence of magnetic dopants on the electronic and chemical environments in topological insulators (TIs) is a key factor when considering possible spintronic applications based on topological surface state properties. Here we provide spectroscopic evidence for the presence of distinct chemical and electronic behavior for surface and bulk magnetic doping of Bi2Te3. The inclusion of Mn in the bulk of Bi2Te3 induces a genuine dilute ferromagnetic state, with reduction of the bulk band gap as the Mn content is increased. Deposition of Fe on the Bi2Te3 surface, on the other hand, favors the formation of iron telluride already at coverages as low as 0.07 monolayer, as a consequence of the reactivity of the Te-rich surface. Our results identify the factors that need to be controlled in the realization of magnetic nanosystems and interfaces based on TIs.

cond-mat.mtrl-sci↗

arXiv2014

The Nature of Surface States on Vicinal Cu (775): An STM and Photoemission Study

We report ARPES and a set of in situ STM measurements on a narrow-terrace-width vicinal Cu(111) crystal surface, Cu(775), whose vicinal cut lies close to the transition between terrace and step modulation. These measurements show sharp zone-folding (or Umklapp) features with a periodicity in k||, indicating that the predominant reference plane is that of Cu(775), i.e. that the surface is predominately step-modulated. Our measurements also show variation in Umklapp intensity with photon energy, which is consistent with prior ARPES experiments on other vicinal Cu(111) surfaces and in agreement with our designation of the state as being step modulated. The measurements also show a weak terrace-modulated state, which, based on several characteristics, we attribute to the presence of terrace widths larger than the ideal terrace width. By measuring the intensity ratio of the two distinct surface-state modulations from PE and the terrace-width distribution from STM, we derive a value for the terrace width, at which the surface-state switches between the two modulations.

cond-mat.mes-hall↗

arXiv2011

Magnetic Proximity Effect as a Pathway to Spintronic Applications of Topological Insulators

Spin-based electronics in topological insulators (TIs) is favored by the long spin coherence1,2 and consequently fault-tolerant information storage. Magnetically doped TIs are ferromagnetic up to 13 K,3 well below any practical operating condition. Here we demonstrate that the long range ferromagnetism at ambient temperature can be induced in Bi2-xMnxTe3 by the magnetic proximity effect through deposited Fe overlayer. This result opens a new path to interface-controlled ferromagnetism in TI-based spintronic devices.

cond-mat.mtrl-sci↗

arXiv2007

X-Ray Analysis of Oxygen-induced Perpendicular Magnetic Anisotropy in Pt/Co/AlOx trilayer

X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx trilayers to investigate the role of Co oxidation in the perpendicular magnetic anisotropy of the Co/AlOx interface. It is observed that high temperature annealing modifies the magnetic properties of the Co layer, inducing an enhancement of the perpendicular magnetic anisotropy. The microscopic structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements. It is shown that annealing enhances the amount of interfacial oxide, which may be at the origin of a strong perpendicular magnetic anisotropy.

cond-mat.mes-hall↗

arXiv2007

Analysis of anisotropy crossover due to oxygen in Pt/Co/MOx trilayer

Extraordinary Hall effect and X-ray spectroscopy measurements have been performed on a series of Pt/Co/MOx trilayers (M=Al, Mg, Ta...) in order to investigate the role of oxidation in the onset of perpendicular magnetic anisotropy at the Co/MOx interface. It is observed that varying the oxidation time modifies the magnetic properties of the Co layer, inducing a magnetic anisotropy crossover from in-plane to out-of-plane. We focused on the influence of plasma oxidation on Pt/Co/AlOx perpendicular magnetic anisotropy. The interfacial electronic structure is analyzed via X-ray photoelectron spectroscopy measurements. It is shown that the maximum of out-of-plane magnetic anisotropy corresponds to the appearance of a significant density of Co-O bondings at the Co/AlOx interface.

cond-mat.mes-hall↗