21 research outputs found
Structural, static and dynamic magnetic properties of CoMnGe thin films on a sapphire a-plane substrate
Magnetic properties of CoMnGe thin films of different thicknesses (13, 34,
55, 83, 100 and 200 nm), grown by RF sputtering at 400{\deg}C on single crystal
sapphire substrates, were studied using vibrating sample magnetometry (VSM) and
conventional or micro-strip line (MS) ferromagnetic resonance (FMR). Their
behavior is described assuming a magnetic energy density showing twofold and
fourfold in-plane anisotropies with some misalignment between their principal
directions. For all the samples, the easy axis of the fourfold anisotropy is
parallel to the c-axis of the substrate while the direction of the twofold
anisotropy easy axis varies from sample to sample and seems to be strongly
influenced by the growth conditions. Its direction is most probably monitored
by the slight unavoidable angle of miscut the Al2O3 substrate. The twofold
in-plane anisotropy field is almost temperature independent, in contrast with
the fourfold field which is a decreasing function of the temperature. Finally,
we study the frequency dependence of the observed line-width of the resonant
mode and we conclude to a typical Gilbert damping constant of 0.0065 for the
55-nm-thick film.Comment: 7 pages, 7 figures, To be published (Journal of Applied Physics
Gate-Controlled Skyrmion Chirality
Magnetic skyrmions are localized chiral spin textures, which offer great
promise to store and process information at the nanoscale. In the presence of
asymmetric exchange interactions, their chirality, which governs their
dynamics, is generally considered as an intrinsic parameter set during the
sample deposition. In this work, we experimentally demonstrate that this key
parameter can be controlled by a gate voltage. We observed that the
current-induced skyrmion motion can be reversed by the application of a gate
voltage. This local and dynamical reversal of the skyrmion chirality is due to
a sign inversion of the interfacial Dzyaloshinskii-Moriya interaction that we
attribute to ionic migration of oxygen under gate voltage. Micromagnetic
simulations show that the chirality reversal is a continuous transformation, in
which the skyrmion is conserved. This gate-controlled chirality provides a
local and dynamical degree of freedom, yielding new functionalities to
skyrmion-based logic devices.Comment: 4 figure
Room temperature chiral magnetic skyrmion in ultrathin magnetic nanostructures
Magnetic skyrmions are chiral spin structures with a whirling configuration.
Their topological properties, nanometer size and the fact that they can be
moved by small current densities have opened a new paradigm for the
manipulation of magnetisation at the nanoscale. To date, chiral skyrmion
structures have been experimentally demonstrated only in bulk materials and in
epitaxial ultrathin films and under external magnetic field or at low
temperature. Here, we report on the observation of stable skyrmions in
sputtered ultrathin Pt/Co/MgO nanostructures, at room temperature and zero
applied magnetic field. We use high lateral resolution X-ray magnetic circular
dichroism microscopy to image their chiral N\'eel internal structure which we
explain as due to the large strength of the Dzyaloshinskii-Moriya interaction
as revealed by spin wave spectroscopy measurements. Our results are
substantiated by micromagnetic simulations and numerical models, which allow
the identification of the physical mechanisms governing the size and stability
of the skyrmions.Comment: Submitted version. Extended version to appear in Nature
Nanotechnolog
First principle calculation of the electronic and magnetic properties of Mn-doped 6H-SiC
The electronic and magnetic properties of 6H-SiC with Mn impurities have been calculated using GGA formalism. Various configurations of Mn sites were considered. It was found that 6H-SiC doped with Mn atoms possess a moment for both types of substitution. The Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. The energy levels appearing in the band gap due to vacancies and due to Mn impurities are determined and the calculated densities of states (DOSs) are used to analyse the different value of the magnetic moments for different types of substitution. A model that explains the magnetic moment at Mn site is proposed
Magnetic Damping and DzyaloshinskiiâMoriya Interactions in Pt/Co<sub>2</sub>FeAl/MgO Systems Grown on Si and MgO Substrates
Spin-pumping-induced damping and interfacial DzyaloshinskiiâMoriya interaction (iDMI) have been studied in Pt/Co2FeAl/MgO systems grown on Si or MgO substrates as a function of Pt and Co2FeAl (CFA) thicknesses. For this, we combined vibrating sample magnetometry (VSM), microstrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS). VSM measurements of the magnetic moment at saturation per unit area revealed the absence of a magnetic dead layer in both systems, with a higher magnetization at saturation obtained for CFA grown on MgO. The key parameters governing the spin-dependent transport through the Pt/CFA interface, including the spin mixing conductance and the spin diffusion length, have been determined from the CFA and the Pt thickness dependence of the damping. BLS has been used to measure the spin wave non-reciprocity via the frequency mismatch between the Stokes and anti-Stokes lines. iDMI has been separated from the contribution of the interface perpendicular anisotropy difference between Pt/CFA and CFA/MgO. Our investigation revealed that both iDMI strength and spin pumping efficiency are higher for CFA-based systems grown on MgO due to its epitaxial growth confirmed by MS-FMR measurements of the in-plane magnetic anisotropy. This suggests that CFA grown on MgO could be a promising material candidate as a spin injection source via spin pumping and for other spintronic applications
Magnetic Damping and Dzyaloshinskii–Moriya Interactions in Pt/Co2FeAl/MgO Systems Grown on Si and MgO Substrates
Spin-pumping-induced damping and interfacial Dzyaloshinskii–Moriya interaction (iDMI) have been studied in Pt/Co2FeAl/MgO systems grown on Si or MgO substrates as a function of Pt and Co2FeAl (CFA) thicknesses. For this, we combined vibrating sample magnetometry (VSM), microstrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS). VSM measurements of the magnetic moment at saturation per unit area revealed the absence of a magnetic dead layer in both systems, with a higher magnetization at saturation obtained for CFA grown on MgO. The key parameters governing the spin-dependent transport through the Pt/CFA interface, including the spin mixing conductance and the spin diffusion length, have been determined from the CFA and the Pt thickness dependence of the damping. BLS has been used to measure the spin wave non-reciprocity via the frequency mismatch between the Stokes and anti-Stokes lines. iDMI has been separated from the contribution of the interface perpendicular anisotropy difference between Pt/CFA and CFA/MgO. Our investigation revealed that both iDMI strength and spin pumping efficiency are higher for CFA-based systems grown on MgO due to its epitaxial growth confirmed by MS-FMR measurements of the in-plane magnetic anisotropy. This suggests that CFA grown on MgO could be a promising material candidate as a spin injection source via spin pumping and for other spintronic applications
Bragg-type Brillouin spectroscopy of spin waves on ultrathin nickel nanowires
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Dzyaloshinskii-Moriya interaction induced asymmetry in dispersion of magnonic Bloch modes
We report the results of the experimental investigation of magnonic Bloch modes in the presence of asymmetric dispersion induced by the interfacial Dzyaloshinskii-Moriya interaction by means of Brillouin light-scattering technique. It was realized in a specially designed ultrathin CoFeB/Pt periodic structure consisting of an array of rectangular nanostrips separated by half-etched grooves. The proposed theory based on the coupled mode approach explains the major features observed experimentally, such as Brillouin zone folding and the asymmetry of the magnonic band-gap points in the reciprocal k space
Magnetic properties of devicelike cobalt/2D materials interfaces
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