Search results for "Magnetic circular dichroism"
showing 10 items of 86 documents
Structure and Microscopic Magnetism of Epitaxial Ni-Mn-Ga Films
2012
We report on the structural and magnetic properties of epitaxial thin films of the ferromagnetic shape memory material Ni–Mn–Ga prepared by DC magnetron sputter deposition. Different substrate materials, i.e., MgO(100) and Al2O3(11−20) allow for a tailored epitaxial growth. Using a sacrificial chromium buffer layer freestanding epitaxial films are obtained. In combination with photolithography partially freestanding structures such as microbridges are fabricated. The complex martensite crystal structure in substrate-constrained and freestanding films is studied by means of X-ray diffraction. The identified asymmetric twin variant configuration is associated with a macroscopic surface patter…
DETECTION LIMITS FOR NATURAL CIRCULAR-DICHROISM OF CHIRAL COMPLEXES IN THE X-RAY RANGE
1993
Whereas both Magnetic Circular Dichroism and Faraday Rotation studies have been successfully carried out at the K-, L- and M-absorption edges of metal atoms in ferromagnetic systems, Natural optical activity of chiral complexes has not yet been detected quite unambiguously in the X-ray range. We review a number of theoretical arguments which confirm that the optical asymmetry factor gσ should be very small in the X-ray range for unoriented powdered samples, especially at the K-absorption edges. This stimulating challenge prompted us to start an intensive programme of measurements aimed at detecting natural circular dichroism in both the soft and “firm” X-ray ranges. Although some of our ex…
Investigation of Co$_2$FeSi: The Heusler compound with Highest Curie Temperature and Magnetic Moment
2006
This work reports on structural and magnetic investigations of the Heusler compound Co$_2$FeSi. X-Ray diffraction and M\"o\ss bauer spectrometry indicate an ordered $L2_1$ structure. Magnetic measurements by means of X-ray magnetic circular dichroism and magnetometry revealed that this compound is, currently, the material with the highest magnetic moment ($6 \mu_B$) and Curie-temperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets.
Electrically Driven Magnetic Domain Wall Rotation in Multiferroic Heterostructures to Manipulate Suspended On-Chip Magnetic Particles
2015
In this work, we experimentally demonstrate deterministic electrically driven, strain-mediated domain wall (DW) rotation in ferromagnetic Ni rings fabricated on piezoelectric [Pb(Mg1/3Nb2/3)O3]0.66-[PbTiO3]0.34 (PMN-PT) substrates. While simultaneously imaging the Ni rings with X-ray magnetic circular dichroism photoemission electron microscopy, an electric field is applied across the PMN-PT substrate that induces strain in the ring structures, driving DW rotation around the ring toward the dominant PMN-PT strain axis by the inverse magnetostriction effect. The DW rotation we observe is analytically predicted using a fully coupled micromagnetic/elastodynamic multiphysics simulation, which v…
Optical and magneto‐optical studies of Mn‐activated LiBaF 3
2005
The photoluminescence (PL) of Mn-doped LiBaF3 shows a weak Mn2+ emission band at 710 nm; the corresponding excitation bands are between 210 and 620 nm. After X-irradiation the PL spectrum shows two new bands peaking at 600 and 670 nm that are tentatively assigned to perturbed Mn2+ emissions; the intensity of all PL bands is increased. Magnetic circular dichroism (MCD) and the MCD-detected electron paramagnetic resonance (EPR) measurements show that F-type centres are formed after X-irradiation. The EPR measurements indicate that there is a spatial correlation between the F-type centre and the Mn2+ dopant. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiplet coupling and band structure in L2,3-edge XAS through multi-channel multiple scattering theory.
2009
International audience; Using the recently developed multi-channel multiple scattering (MCMS) method we have calculated the x-ray absorption spectra (XAS) at the L2,3-edge of transition metal compounds. The MCMS method is an ab initio scheme which combines an accurate description of the band structure of the material with a correlated many-electron wave function on the absorber atom. Thereby configuration interaction in the XAS final state, in particular multiplet effects, can be taken into account. In the present implementation, we use an electron-hole wave function and treat the interaction with all other electrons on a mean-field level. The calculated spectra agree well with experiment f…
Absence of element specific ferromagnetism in Co doped ZnO investigated by soft X-ray resonant reflectivity
2010
On the quest for the intrinsic origin of ferromagnetism (FM) in ZnO doped with a few percent transition metal, we show detailed X-ray resonant magnetic reflectivity (XRMR) measurements, performed at the Co L2,3 and the O K edges of pulsed laser deposition (PLD) prepared samples. These samples show ferromagnetism at room temperature (RT) (QUID: about 2μB /Co). But in contrast to the QUID measurements, element specific reflection measurements as a function of angle (θ-2θ scans) and energy (const. qz) do not show any sign of ferromagnetism. Therefore, we can exclude without doubt Co as a possible origin for FM in this system. Our results are in perfect agreement with earlier published XMCD dat…
Magnetic ordering in an (Fe0.2Cr0.8)1.5[Cr(CN)6] Prussian blue analogue studied with synchrotron radiation based spectroscopies
2018
The appearance of magnetic order in the (Fe0.2Cr0.8)1.5[Cr(CN)6]·15H2O Prussian blue analogue at low temperature has been investigated by means of synchrotron radiation-based X-ray absorption spectroscopy and X-ray magnetic circular dichroism. With the help of ligand field multiplet analysis we have been able to identify the oxidation states of the metallic cations present in the sample and their evolution with temperature. Our experiments reveal that the appearance of ferromagnetic order is triggered by the transformation of CrIII cations to CrII high-spin caused by a transfer of electrons from the Fe to the Cr resulting in an increase of the magnetic interactions within the (Cr, Cr) subla…
X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components
2011
X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR s…
Giant magnetic anisotropy energy and coercivity in Fe island and atomic wire on W(110)
2012
We have directly investigated the giant magnetic anisotropy energy and coercivity of monolayer (ML) Fe islands and stripes on flat and stepped W(110) surfaces using x-ray magnetic circular dichroism. Both for islands and stripes, the magnetic anisotropy energy is $\ensuremath{\sim}$1.0 meV/atom, independent of the coverage below 0.5 ML. On the contrary, the coercive field of the islands rapidly drops from 4.3 T at 0.25 ML to 1.9 T at 0.50 ML, while that of the stripes moderately degrades from 3.5 T at 0.15 ML ($\ensuremath{\sim}$3 atom rows) to 3.0 T at 0.50 ML. We explain the contrastive behavior for the islands and stripes by different nucleation and remagnetization processes. Considering…