13 research outputs found
Design and realization of a sputter deposition system for the \textit{in situ-} and \textit{in operando-}use in polarized neutron reflectometry experiments
We report on the realization of a sputter deposition system for the in situ-
and in operando-use in polarized neutron reflectometry experiments. Starting
with the scientific requirements, which define the general design
considerations, the external limitations and boundaries imposed by the
available space at a neutron beamline and by the neutron and vacuum
compatibility of the used materials, are assessed. The relevant aspects are
then accounted for in the realization of our highly mobile deposition system,
which was designed with a focus on a quick and simple installation and
removability at the beamline. Apart from the general design, the in-vacuum
components, the auxiliary equipment and the remote control via a computer, as
well as relevant safety aspects are presented in detail.Comment: Submitted for publication in Nuclear Inst. and Methods in Physics
Research, A. (1st revised version
Electronic Correlations in Vanadium Revealed by Electron-Positron Annihilation Measurements
The electronic structure of vanadium measured by Angular Correlation of
electron-positron Annihilation Radiation (ACAR) is compared with the
predictions of the combined Density Functional and Dynamical Mean-Field Theory
(DMFT). Reconstructing the momentum density from five 2D projections we were
able to determine the full Fermi surface and found excellent agreement with the
DMFT calculations. In particular, we show that the local, dynamic self-energy
corrections contribute to the anisotropy of the momentum density and need to be
included to explain the experimental results
Spin-resolved fermi surface of the localized ferromagnetic Heusler compound Cu2MnAl measured with spin-polarized positron annihilation
We determined the bulk electronic structure in the prototypical Heusler
compound CuMnAl by measuring the Angular Correlation of Annihilation
Radiation (2D-ACAR) using spin-polarized positrons. To this end, a new
algorithm for reconstructing 3D densities from projections is introduced that
allows us to corroborate the excellent agreement between our electronic
structure calculations and the experimental data. The contribution of each
individual Fermi surface sheet to the magnetization was identified, and summed
to a total spin magnetic moment of
Two-Dimensional Magnets: Forgotten History and Recent Progress towards Spintronic Applications
The recent discovery of 2D magnetic order in van der Waals materials has stimulated a renaissance in the field of atomically thin magnets. This has led to promising demonstrations of spintronic functionality such as tunneling magnetoresistance. The frantic pace of this emerging research, however, has also led to some confusion surrounding the underlying phenomena of phase transitions in 2D magnets. In fact, there is a rich history of experimental precedents beginning in the 1960s with quasi-2D bulk magnets and progressing to the 1980s using atomically thin sheets of elemental metals. This review provides a holistic discussion of the current state of knowledge on the three distinct families of low-dimensional magnets: quasi-2D, ultrathin films, and van der Waals crystals. It highlights the unique opportunities presented by the latest implementation in van der Waals materials. By revisiting the fundamental insights from the field of low-dimensional magnetism, this review highlights factors that can be used to enhance material performance. For example, the limits imposed on the critical temperature by the Mermin-Wagner theorem can be escaped in three separate ways: magnetocrystalline anisotropy, long-range interactions, and shape anisotropy. Several recent experimental reports of atomically thin magnets with Curie temperatures above room temperature are highlighted
Indications for Dzyaloshinskii-Moriya interaction at the Pd/Fe interface studied by in situ polarized neutron reflectometry
Using \textit{in situ} polarized neutron reflectometry, the depth resolved
evolution of the magnetism and structure in a Pd/Fe/Pd trilayer thin-film is
measured during growth. The initial film structure of Pd/Fe shows a small
proximity induced magnetism in the underlayer and a magnetization in the Fe
layer of \, per Fe atom, less than the expected
bulk value of \,. Deposition of the Pd capping layer
initially follows an island-like growth mode with subsequent coalescence. With
increasing Pd deposition the Fe moment and the proximity-induced magnetism in
the Pd capping layer decrease. After final deposition of the Pd capping layer,
the magnetic profile is structurally and magnetically symmetric across the Fe
layer, with magnetism induced in Pd up to 0.92 \,nm from the interface.
Throughout the Pd deposition the Pd/Fe/Pd trilayer structure is becoming
increasingly symmetric, a fact which points to a Dzyaloshinskii-Moriya
interaction as a likely cause of the observed magnetic behavior.Comment: Submitted for publication in PRB (original version) on April 17, 201