Search

Asymmetrically sandwiched thin magnetic layers with perpendicular anisotropy and Dzyaloshinskii-Moriya interaction (DMI) is the prospective material science platform for spin-orbitronic technologies that rely on the motion of chiral magnetic textures, like skyrmions or chiral domain walls (DWs). The dynamic performance of a DW-based racetrack is defined by the strength of the DMI and the DW damping. The determination of the latter parameter is typically done based on technically challenging DW motion experiments. Here, we propose a method to access both the DMI constant and DW damping from static experiments by monitoring the tilt of magnetic DWs in nanostripes. We experimentally demonstrate that in perpendicularly magnetized ${\mathrm{//Cr}\mathrm{O}}_{x}\mathrm{/Co/Pt}$ stacks, DWs can be trapped on edge roughness in a metastable tilted state as a result of the DW dynamics driven by an external magnetic field. The measured tilt can be correlated to the DMI strength and DW damping in a self-consistent way in the frame of a theoretical formalism based on the collective coordinate approach.

The optical control of magnetism offers an attractive possibility to manipulate small magnetic domains for prospective memory devices on ultrashort time scales. Here, we report on the local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers controlled only by the helicity of ultrashort laser pulses. Relying on the experimentally determined average size of stripe domains and the magnetic layer thickness, we calculate the temperature and characteristic fields at which the stripe-bubble transformation occurs. Furthermore, we demonstrate that in the narrow range of the laser power, the helicity induces a drag on domain walls.

Ultrathin asymmetrically sandwiched ferromagnetic films can support magnetic skyrmions and skyrmion bubbles, which are eyed as functional units for tomorrow's spintronic logic and memory devices. The type of object and its size and mobility are set by intrinsic magnetic parameters, which are largely unknown. The authors demonstrate that the exchange stiffness of ultrathin films can be determined by analysis of the temperature dependence of magnetization. This simple yet robust approach is crucial not only for the experimental community but also for theorists, as it determines domain-wall thickness, the period of a Dzyaloshinskii spiral, and the characteristic magnetic length.

The main origin of the chiral symmetry breaking and, thus, for the magnetochiral effects in magnetic materials is associated with an antisymmetric exchange interaction, the intrinsic Dzyaloshinskii-Moriya interaction (DMI). Recently, numerous inspiring theoretical works predict that the bending of a thin film to a curved surface is often sufficient to induce similar chiral effects. However, these originate from the exchange or magnetostatic interactions and can stabilize noncollinear magnetic structures or influence spin-wave propagation. Here, we demonstrate that curvature-induced chiral effects are experimentally observable rather than theoretical abstraction and are present even in conventional soft ferromagnetic materials. We show that, by measuring the depinning field of domain walls in the simplest possible curve, a flat parabolic stripe, the effective exchange-driven DMI interaction constant can be quantified. Remarkably, its value can be as high as the interfacial DMI constant for thin films and can be tuned by the parabola's curvature.

Typically, the chiral magnetic Skyrmion is a single-state excitation. Here we propose a system, where multiplet of Skyrmion states appears and one of these states can be the ground one. We show that the presence of a localized curvilinear defect drastically changes the magnetic properties of a thin perpendicularly magnetized ferromagnetic film. For a large enough defect amplitude a discrete set of equilibrium magnetization states appears forming a ladder of energy levels. Each equilibrium state has either a zero or a unit topological charge; i.e., topologically trivial and Skyrmion multiplets generally appear. Transitions between the levels with the same topological charge are allowed and can be utilized to encode and switch a bit of information. There is a wide range of geometrical and material parameters, where the Skyrmion level has the lowest energy. Thus, periodically arranged curvilinear defects can result in a Skyrmion lattice as the ground state.

Isotope shift relative to $^{209}\mathrm{Bi}$ and hyperfine splitting for $^{211,213}\mathrm{Bi}$ have been measured by in-source laser spectroscopy at the 306.77-nm atomic transition. The pronounced shell effect both in radii and magnetic moments in Bi isotopes at $N=126$ has been observed. The isotopic trend of magnetic moment for $9/{2}^{\ensuremath{-}}$ ground states of even-$N$ Bi isotopes has been qualitatively explained by the change in the first-order core-polarization correction. The possible influence of the octupole degree of freedom on the magnetic moment behavior at $Ng126$ has been discussed.

In-source laser spectroscopy experiments for bismuth isotopes at the 306.77-nm atomic transition has been carried out at the Investigation of Radioactive Isotopes on Synchrocyclotron facility of Petersburg Nuclear Physics Institute. New data on isotope shifts and hyperfine structure for Bi ground states and isomers $(^{189,190\mathrm{m}1,190\mathrm{m}2,191,192,192\mathrm{m},194,194\mathrm{m},198\mathrm{m}}\mathrm{Bi})$ have been obtained. The changes in the mean-square charge radii $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}$ and magnetic-moment values have been deduced. For Bi nuclei a marked deviation from the isotopic trend of $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}$ in lead and thallium isotopic chains has been demonstrated at $N\phantom{\rule{0.16em}{0ex}}l\phantom{\rule{0.16em}{0ex}}111$. This has been interpreted as an indication of the onset of quadrupole deformation. Analysis of the magnetic moments for odd-odd Bi isotopes also points to the possible increase in deformation at $N\phantom{\rule{0.16em}{0ex}}l\phantom{\rule{0.16em}{0ex}}111$.

In-source laser spectroscopy experiments on bismuth isotopes using the 306.77-nm atomic transition have been carried out at the Investigation of Radioactive Isotopes on Synchrocyclotron facility of the Petersburg Nuclear Physics Institute. New data for the isotope shifts and hyperfine structures of $^{193,195,197}\mathrm{Bi}^{\mathrm{g},\mathrm{m}}$ isotopes and isomers have been obtained. A large isomer shift between $I=1/{2}^{+}$ (intruder) and $I=9/{2}^{\ensuremath{-}}$ (normal) states has been found. The charge radii of the $^{193,195,197}\mathrm{Bi}$ ground states follow the trend found previously for isotonic (spherical) lead nuclei. The larger radii for the $1/{2}^{+}$ isomers suggest a larger deformation of these isomers compared to the ground state and support the shape coexistence interpretation of the previously obtained experimental data. Magnetic moments of Bi intruder isomers depart from the trend of the magnetic moments of the $1/{2}^{+}$ thallium ground states at $Nl114$.

The local-field effects are considered which are feasible in a dense ensemble of resonant atoms modeled by multilevel quantum systems. Our approach is based on the generalized two-level system @V.S. Butylkin, A.E. Kaplan, and Yu.G. Khronopulo, Zh. Eksp. Teor. Fiz. 59, 921 ~1970!#. Making use of this model, we take account of the nonresonant polarization and Stark shift of the absorption line due to the difference in linear polarizabilities of atoms in ground and excited states. With near dipole-dipole interaction and quadratic Stark effect included simultaneously, new features of the hysteresis behavior of the population difference as a function of the external-field intensity are predicted. @S1050-2947~99!01504-8#

In-source laser spectroscopy experiments for neutron-deficient thallium isotopes at the 276.9-nm atomic transition have been carried out at the Investigation of Radioactive Isotopes on Synchrocyclotron facility of Petersburg Nuclear Physics Institute. New data on isotope shifts and the hyperfine structure for ${}^{183\ensuremath{-}207}$Tl isotopes and isomers are presented. The changes in the mean-square charge radii and magnetic-moment values are deduced. It is shown that nuclear properties of Tl isotopes and isomers smoothly change at the neutron midshell and beyond without development of strong deformation in contrast to the adjacent Hg nuclei. A rather great isomer shift between $I$ $=$ 1/2 and $I$ $=$ 9/2 states for odd Tl isotopes is preserved for both sides of the previously investigated mass range. For the first time, a similar isomer shift is found for the odd-odd isotope ${}^{186}$Tl. The close resemblance of the charge radii isotopic behavior for the Tl and Pb ground states is demonstrated.

Magnetization behavior of long nanowires with square cross-section under influence of strong perpendicular spin-polarized current is studied theoretically. The study is based on Landau-Lifshitz-Slonczewski phenomenology. In the no current case the wire is magnetized uniformly along its axis. For small currents the wire magnetization remains uniform but it inclines with respect to the wire axis within the plane perpendicular to the current direction. With the current increasing the inclination angle increases up to the maximum value $\pi/4$. Further current increase leads either to saturation or to stable periodic multidomain structure depending on the wire thickness. For thick wires a hysteresis is observed in the saturation process under the action of current. All critical parameters of the current induced magnetization behavior are determined theoretically. The study is carried out both analytically and using micromagnetic simulations., Comment: 9 pages, 5 figures

This paper describes measurements on the isotopes (75,77,78)Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the ...

Influence of the spin-transfer torque on the vortex state magnetic nanodisk is studied numerically via the Slonczewski-Berger mechanism. The existence of a critical current is determined for the case of same-directed electrical current, its spin polarization, and the polarity of the vortex. The critical current separates two regimes: (i) deformed but static vortex state and (ii) essentially dynamic state under which the spatiotemporal periodic structures can appear. The structure is a stable vortex-antivortex lattice. Symmetry of the lattice depends on the applied current value, and for high currents (close to saturation) only square lattices are observed. General relations for size of the stable lattice are obtained analytically.

We report the first confirmation of the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained values are mu(71Cu)=+2.2747(8)mu(N), mu(73Cu)=+1.7426(8)mu(N), and mu(75Cu)=+1.0062(13)mu(N) corresponding to spins I=3/2 for 71,73Cu and I=5/2 for 75Cu. The results are in fair agreement with large-scale shell-model calculations.

The branching of the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ transition in $^{92}\mathrm{Sr}$ has been measured to 0.032(4) per $^{92}\mathrm{Rb}$ decay. It confirms an earlier measurement which was discarded in nuclear data evaluations because of a contradiction with accepted lower log $\mathit{ft}$ limits. The conflict could be solved assuming that close to half of the decay intensity, mostly as high-energy ground-state transitions, is missing in the decay scheme.

In-target resonance ionization was applied for the first time, to our knowledge, for isotope-shift and hyperfine splitting measurements at the Investigation of Radioactive Isotopes on Synchrocyclotron (IRIS) facility. The production yield of the short-lived Gd atoms and the selectivity of the laser ionization appear to be nearly two and seven times higher, respectively, compared with those of a conventional target--laser-ion-source system. Changes in mean-square charge radii $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}{}_{A,{A}^{'}}$ for $^{145}\mathrm{Gd}$,$^{145}\mathrm{Gd}{}^{m}$, and $^{143}\mathrm{Gd}{}^{m}$ and magnetic moments for $^{145}\mathrm{Gd}$ and $^{143}\mathrm{Gd}{}^{m}$ are determined. The stabilization influence of the proton subshell closure on the $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}{}_{A,{A}^{'}}$ (i.e., on the deformation) behavior at $Nl82$ was not observed.