Publications de Pietro Gambardella

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Magnetic impurities in solids cause manifold changes in their macroscopic properties, such as anomalous low temperature resistance due to Kondo screening, reduction of the superconducting transition temperature due to local suppression of the order paramet ...

This thesis describes experiments with one-dimensional atomic chains grown by step decoration of vicinal Pt surfaces. The objective of the research was twofold: first, to characterize metal epitaxial growth on stepped substrates; second, to make use of this knowledge to fabricate arrays of monatomic metal wires in order to investigate their electronic and magnetic properties. The first part focuses on molecular beam epitaxy (MBE) of Ag, Cu, Co, and Ni on densely stepped Pt surfaces (one monatomic step every

We show that double-resonance spectra recorded during the simultaneous absorption of x-ray and microwave (MW) photons are a fingerprint of the perturbed electronic configuration of atomic species driven to ferromagnetic resonance. X-ray absorption measurem ...

Nanomagnets of controlled size, organized into regular patterns open new perspectives in the fields of nanoelectronics, spintronics, and quantum computation. Self-assembling processes on various types of substrates allow designing fine-structured architect ...

The chapter “Magnetism of low-dimensional metallic structures” reviews experiments on the magnetism of surface-supported low-dimensional structures of 3d metals. Controlling the static and dynamic magnetic behavior of both individual impurities and supported nanostructures on nonmagnetic surfaces represents a fundamental challenge as well as a prerequisite to design magnetic storage and logic devices of novel conception. We describe the governing principles of self-organized growth of metallic nanostructure

We present a method to measure continuous-wave ferromagnetic resonance (FMR) spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium-iron-garnet sam ...

We report on the magnetic coupling between isolated Co atoms as well as small Co islands and Ni(111) mediated by an epitaxial graphene layer. X-ray magnetic circular dichroism and scanning tunneling microscopy combined with density functional theory calcul ...

We report on a combined experimental and theoretical investigation of the magnetic anisotropy of Fe and Co ultrathin layers on strongly polarizable metal substrates. Monolayer (ML) films of Co and Fe on Rh(111) have been investigated in situ by x-ray magnetic circular dichroism (XMCD), magneto-optic Kerr effect, and scanning tunneling microscopy. The experiments show that both magnetic adlayers exhibit ferromagnetic order and enhanced spin and orbital moments compared to the bulk metals. The easy magnetizat

Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-h

We investigate the effect of H adsorption on the magnetic properties of individual Co atoms on Pt(111) with scanning tunneling microscopy. For pristine Co atoms, we detect no inelastic features in the tunnel spectra. Conversely, CoH and CoH2 show a number of low-energy vibrational features in their differential conductance identified by isotope substitution. Only the fcc-adsorbed species present conductance steps of magnetic origin, with a field splitting identifying their effective spin as S-eff = 2 for Co

Ultrathin Fe films on Pt substrates have been investigated under ultrahigh vacuum conditions by scanning tunneling microscopy, low energy electron diffraction, magneto-optical Kerr effect, x-ray magnetic circular dichroism measurements, and Kerr microscopy ...

We report x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements as well as multiplet calculations for Dy, Ho, Er, and Tm atoms adsorbed on Pt(111), Cu(111), Ag(100), and Ag(111). In the gas phase, all four elements are divalent a ...

We report on the magnetic properties of Fe and Co adatoms on a Cu2N/Cu(100)-c(2 x 2) surface investigated by x-ray magnetic dichroism measurements and density functional theory (DFT) calculations including the local coulomb interaction. We compare these results with properties formerly deduced from STM spin excitation spectroscopy (SES) performed on the individual adatoms. In particular we focus on the values of the local magnetic moments determined by XMCD compared to the expectation values derived from th

We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zer ...

A permanent magnet retains a substantial fraction of its saturation magnetization in the absence of an external magnetic field. Realizing magnetic remanence in a single atom allows for storing and processing information in the smallest unit of matter. We s ...

We investigated the magnetic properties of individual Ho atoms adsorbed on the (111) surface of Pt, which have been recently claimed to display single ion magnetic behavior. By combining x-ray absorption spectroscopy and magnetic dichroism measurements with ligand field multiplet calculations, we reveal a ground state which is incompatible with long spin relaxation times, in disagreement with former findings. A comparative study of the ground state and magnetic anisotropy of Ho and Er on Pt(111) and Cu(111)

We investigate the spin relaxation of Ho single atom magnets on MgO/Ag(100) as a function of temperature and magnetic field. We find that the spin relaxation is thermally activated at low field, while it remains larger than 1000 s up to 30 K and 8 T. This ...

High-density arrays (5 x 10(6) cm(-1)) of parallel nanowires have been grown using the vicinal Pt(997) surface as a template. Single monatomic rows of Ag and Cu can be deposited with subrow precision. We demonstrate real-time monitoring and characterization of the growth of the atomic chains as a function of temperature by thermal energy helium atom scattering. Scanning tunneling microscopy provides further insight into the structure of the metal rows. Growth mode and alloying with the Pt substrate are disc

We performed a combined theoretical and experimental investigation of the orbital magnetism and magnetocrystalline anisotropy of isolated Co and Fe adatoms on Pd(111) and Rh(111). Theoretical calculations of the spin and orbital moments are based on ab ini ...

The isotropic magnetic moment of a free atom is shown to develop giant magnetic anisotropy energy due to symmetry reduction at an atomically ordered surface. Single cobalt atoms deposited onto platinum ( 111) are found to have a magnetic anisotropy energy of 9 millielectron volts per atom arising from the combination of unquenched orbital moments (1.1 Bohr magnetons) and strong spin-orbit coupling induced by the platinum substrate. By assembling cobalt nanoparticles containing up to 40 atoms, the magnetic a

Pietro Gambardella

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Magnetism of individual atoms adsorbed on surfaces

Growth, electronic structure and magnetism of supported metal nanowires

Double-resonant x-ray and microwave absorption: Atomic spectroscopy of precessional orbital and spin dynamics

Self-Assembled Nanometer-Scale Magnetic Networks on Surfaces: Fundamental Interactions and Functional Properties

Magnetism of Low-dimensional Metallic Structures

X-ray ferromagnetic resonance spectroscopy

Complex Magnetic Exchange Coupling between Co Nanostructures and Ni(111) across Epitaxial Graphene

Magnetic anisotropy of Fe and Co ultrathin films deposited on Rh(111) and Pt(111) substrates: An experimental and first-principles investigation

Reaching the magnetic anisotropy limit of a 3d metal atom

Controlling the Spin of Co Atoms on Pt(111) by Hydrogen Adsorption

Structure and magnetism of atomically thin Fe layers on flat and vicinal Pt surfaces

4 f occupancy and magnetism of rare-earth atoms adsorbed on metal substrates

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms on

Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO

Magnetic remanence in single atoms

Magnetism of Ho and Er Atoms on Close-Packed Metal Surfaces

Unconventional Spin Relaxation Involving Localized Vibrational Modes in Ho Single-Atom Magnets

One-dimensional metal chains on Pt vicinal surfaces

Magnetocrystalline anisotropy energy of Co and Fe adatoms on the (111) surfaces of Pd and Rh

Giant magnetic anisotropy of single cobalt atoms and nanoparticles