Magnetism of epitaxial fcc Fe(100) films on Cu(100) investigated in Situ by conversion-electron Mössbauer spectroscopy in ultrahigh vacuum

Magnetic ground state of face-centered-cubic structure of iron

First principles calculations reveal that the antiferromagnetic double layer (AFMD) along the magnetization direction of 〈0 0 1〉 is the magnetic ground state of face-centered-cubic (FCC) structure of iron (Fe) due to its lowest total energy among all the studied magnetic states. This magnetic ground state of AFMD-〈0 0 1〉 is fundamentally due to a stronger chemical bonding in terms of electronic structure, and could be confirmed by its mechanical properties for the first time. Calculations also show that lattice constant has an important effect to determine the magnetic state of FCC Fe, and a transition of magnetic state between AFMD-〈0 0 1〉 and ferromagnetic happens at the critical lattice constant of 3.666 Å. The derived results are in good agreement with experimental and theoretical observations, and could clarify the controversy regarding magnetic ground state of FCC Fe in the literature.

Applicability of the Strongly Constrained and Appropriately Normed Density Functional to Transition-Metal Magnetism

We find that the recently developed self-consistent and appropriately normed meta-generalized gradient approximation, which has been found to provide highly accurate results for many materials, is, however, not able to describe the stability and properties of phases of Fe important for steel. This is due to an overestimated tendency toward magnetism and exaggeration of magnetic energies, which we also find in other transition metals.

Structure and Magnetic Properties of Aerosol Nanoparticles of Fe and Its Alloys

Structure and magnetic properties of aerosol nanoparticles of Fe and its alloys (FeMn, FeNi, FeNiMn, FePt, FeCr, FeCo, and FeCu) have been reviewed. It has been shown that, compared to a bulk material, the particles have a number of specific features being of much fundamental and applied interest. The effect of both a quenched high-temperature Fe modification and its oxides on the structure and magnetism of nanoparticles has been considered in detail. Particular attention has been paid to the recently observed fine structure in the hyperfine field distribution at iron nuclei in Mössbauer spectra for pure iron and its alloys both as a bulk and aerosol nanoparticles. This phenomenon makes it possible to reveal very weak magnetic interactions in the system under study. The plausible origin of these magnetic interactions has been also discussed.

Shear instability of gamma-Fe in bulk and in ultrathin films

Using ab initio local-spin-density calculations we demonstrate that along the Bain path describing the transformation of face-centered-cubic (fcc) gamma-Fe into body-centered-cubic (bcc) alpha-Fe, tetragonal Fe is unstable against monoclinic shear deformations producing a nearly bcc structure. In the limit of a monolayer adsorbed on a fcc substrate, the epitaxial constraint suppresses the shear instability, but in ultrathin films with three to six monolayers a striped pattern of near-bcc domains develops, confirming recent observations by scanning tunneling microscopy. A strong correlation between the shear instability and the magnetic state is reported.

Theoretical calculation of magnetic properties of ultrathin Fe films on Cu(100)

The temperature dependence of the magnetization in fcc Fe on Cu(100) is calculated using a self-consistent local mean-field theory. The model reproduces an experimental magnetization oscillation as a function of film thickness and supports a picture where the top two layers are ferromagnetically coupled, and the remaining layers are antiferromagnetically coupled. The origin of the puzzling linear temperature dependence in oscillation amplitude is understood as a "surface phenomena" of the antiferromagnetic layer at the Fe/Cu interface. Proximity effects between a thin antiferromagnet with a low Neel temperature and a neighboring ferromagnet with a higher Curie temperature are discussed.