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X-ray circular dichroism (XMCD), one of the main tools to study magnetism, benefits enormously from the capability of a fast alterable helicity of circularly polarized X-ray photons. Here we present a method for boosting the alternating frequency between right- and left-handed photons to the MHz regime, more than three orders of magnitude faster than state-of-the-art technologies. The method is based on a twin elliptical undulator installed in an electron storage ring being operated in a novel mode where the electron optics is tuned close to a resonance with electrons captured in transverse resonance island buckets. Propagating through the twin undulator, electrons from different islands emit photons of the same wavelength but of opposite helicity. These two helicity components can be alternated as fast as 2 ns. In a proof-of-principle experiment at BESSY II, we demonstrate XMCD at the L2,3 absorption edges of Ni with an 800 ns helicity flip. Rapidly switching the helicity of polarised x-rays is desirable for studying magnetic dynamics via circular dichroism spectroscopy, but has not yet been realised from synchrotron radiation sources. Here, switching between ultrafast emission of monoenergetic, circularly polarized x-rays with opposite helicity is shown within a few nanoseconds. [ABSTRACT FROM AUTHOR]

We report on THz absorption spectroscopy combined with high magnetic fields of polycrystalline RCrO 3 (R = Pr, Sm, Er) aiming understanding spin wave resonances at their low temperature magnetic phases. Our measurements show that the temperature , and the implicit anisotropies at which the Cr 3+ spin reorientation at T SR takes place, are determinant on the ferromagnetic-like (FM) and the antiferromagnetic-like (AFM) spin modes being optically active. It is found that they are dependent on Rare Earth 4 f moment and ion size. We also studied temperature and field dependence of crystal field levels in the same spectroscopic region. Pr 3+ non-Kramers emerges at 100 K and Zeeman splits. An observed absence of spin wave resonances in PrCrO 3 is attributed to Pr 3+ remaining paramagnetic. In SmCrO 3 near cancelation of the spin and orbital moments is proposed as the possible reason for not detecting Sm 3+ ground state transitions. Here, the FM and AFM resonant modes harden when the temperature decreases and split linearly under applied fields at 5 K and below. In ErCrO 3 the Er 3+ Kramers doublet becomes active at about the T SR onset. Each line further experiences Zeeman splitting under magnetic fields while an spin reversal induced by a ∼2.5 T field, back to the Γ 4 (F z ) from the Γ 1 phase at 2 K, produces a secondary splitting. The 5 K AFM and FM excitations in ErCrO 3 have a concerted frequency-intensity temperature dependence and a shoulder pointing to the Er 3+ smaller ion size also disrupting the two magnetic sublattice approximation. Both resonances reduce to one when the temperature is lowered to 2 K in the Γ 1 representation. Our findings have important implications on the complex interplay in the magneto-electrodynamics associated with the Rare-Earth 4 f – 3d transition metal spin coupling and the structural A site instabilities in perovskite multiferroics. [ABSTRACT FROM AUTHOR]

We describe frequency-domain Fourier-transform THz-EPR as a method to assign spin-coupling parameters of high-spin ( S > 1/2) systems with very large zero-field splittings. The instrumental foundations of synchrotron-based FD-FT THz-EPR are presented, alongside with a discussion of frequency-domain EPR simulation routines. The capabilities of this approach is demonstrated for selected mono- and multinuclear HS systems. Finally, we discuss remaining challenges and give an outlook on the future prospects of the technique. [ABSTRACT FROM AUTHOR]

Scattering methods are widely used to characterize the structure and constituents of matter on small length scales. This motivates this introductory text on identifying prospective approaches to scattering-based methods for granular media. A survey to light scattering by particles and particle ensembles is given. It is elaborated why the established scattering methods using X-rays and visible light cannot in general be transferred to granular media. Spectroscopic measurements using terahertz radiation are highlighted as they probe the scattering properties of granular media, which are sensitive to the packing structure. Experimental details to optimize a spectrometer for measurements on granular media are discussed. We perform transmission measurements on static and agitated granular media using Fourier transform spectroscopy at the THz beamline of the Bessy II storage ring. The measurements demonstrate the potential to evaluate degrees of order in the media and to track transient structural states in agitated bulk granular media. [ABSTRACT FROM AUTHOR]

THz extinction spectroscopy extends UV-Vis and NIR-spectroscopy to characterize particles from fine powders and dust to sand, grains and granulated materials. We extract particle sizes from the spectral position of the first peak of the interference structure and size distributions from the visibility of the fine ripple structure in the measured extinction spectra. As such, we can demonstrate a route for a quick determination of these parameters from single measurements. [ABSTRACT FROM AUTHOR]

The article presents upgrades of femtoslicing facility at Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung mbh (BESSY II) in Berlin, Germany in 2014. It discusses the use of femtosecond-laser system that comprises two amplifiers seeded by one Ti:Sa oscillator. It highlights the operation of FemtoSpeX facility as user facility that enables experiments in the field of transient phenomena and ultrafast magnetism.

Abstract: A novel design of high load capacity multiaxis positioning stages with an accuracy in the range of nanometers is presented. For strokes of some 10mm with no play and high stiffness a general design principle supporting six Cartesian degrees of freedom has been developed using a new parallel kinematic topology based on trapezoidal arrangements. It was developed together with novel flexures and drives for synchrotron optics in ultrahigh vacuum at BESSY. The performance of the setup and its kinematic properties are described as well as high-resolution measurements of the six motions and their crosstalk. Applications of the design have been in daily operation since 1998. Since then, more than 30 derivates have been implemented with outstanding characteristics and excellent reliability. [Copyright &y& Elsevier]

We present the development of fast transmissive center-of-mass x-ray beam position monitors with a large active area, based on a thinned position sensitive detector in both a duo- and a tetra-lateral variant. The detectors were tested at BESSY beamlines BL14.1, KMC-1, and KMC-2 and yielded signal currents of up to 3 μA/100 mA ring current at 10 keV photon energy using the monochromatic focused beam of BL14.1. The active area sizes were 1×1 and 3×3 mm2 for the duo-lateral and 5×5 mm2 for the tetra-lateral devices, with the duo-lateral detectors currently being available in sizes from 1×1 to 10×10 mm2 and thicknesses between 5 and 10 μm. The presented detectors’ thicknesses were measured to be 5 and 8 μm with a corresponding transmission of up to 93% at 10 keV and 15% at 2.5 keV. Up to a detection bandwidth of 10 kHz, the monitors provide submicron position resolution. For lower detection bandwidths, the signal-to-noise reaches values of up to 6×104 at 10 Hz, corresponding to a position resolution of better than 50 nm for both detector sizes. As it stands, this monitor design approach promises to be a generic solution for automation of state-of-the-art crystal monochromator beamlines. [ABSTRACT FROM AUTHOR]

Over more than a century, X-rays have transformed our understanding of the fundamental structure of matter and have been an indispensable tool for chemistry, physics, biology, materials science and related fields. Recent advances in ultrafast X-ray sources operating in the femtosecond to attosecond regimes have opened an important new frontier in X-ray science. These advances now enable: (i) sensitive probing of structural dynamics in matter on the fundamental timescales of atomic motion, (ii) element-specific probing of electronic structure and charge dynamics on fundamental timescales of electronic motion, and (iii) powerful new approaches for unravelling the coupling between electronic and atomic structural dynamics that underpin the properties and function of matter. Most notable is the recent realization of X-ray free-electron lasers (XFELs) with numerous new XFEL facilities in operation or under development worldwide. Advances in XFELs are complemented by advances in synchrotronbased and table-top laser-plasma X-ray sources now operating in the femtosecond regime, and laser-based high-order harmonic XUV sources operating in the attosecond regime. [ABSTRACT FROM AUTHOR]

The chemical state of thermochemically treated chromium(III) oxide (Cr2O3) with various carbonates was analyzed by far-infrared (far-IR) spectroscopy (spectral region 700-25 cm−1). Non-toxic Cr2O3was oxidized with potassium, sodium, and calcium carbonate, respectively, to toxic Cr(VI) and Cr(V) compounds during thermal treatment at 1000 °C. In reverse, thermochemical treatment of Cr2O3with magnesium carbonate lead to the formation of the Cr(III) compound MgCr2O4. Higher temperatures (>1200 °C) or reducing atmospheric conditions prevent the formation of Cr(VI)/Cr(V) compounds, too. Additionally, it was found that polyethylene powder with a low particle size (<70 μm) is favorable for the collection of good far-IR spectra of inorganic powders. [ABSTRACT FROM AUTHOR]

We present general expressions for the magnetic transition rates in electron paramagnetic resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (5 = 5/2) FeIII in hemin from the polarization dependence of experimental EPR line intensities. [ABSTRACT FROM AUTHOR]

Liquid-vapor and liquid-solid interfaces drive numerous important processes in the environment and technology, such as the sequestration of CO SB 2 sb by the oceans, the uptake and release of trace gases by aerosol droplets, the corrosion of metals, and reactions in electrochemical energy conversion and storage devices. Because of the low-energy capabilities of the branchline, a differentially pumped X-ray beam entry will be realized enabling X-ray absorption at the Li K-edge; for higher X-ray energies, a gate-valve mounted SiNx window will be used to separate the vacuum in the beamline from the gas atmosphere in the endstation. Endstation concept for the low-energy branch Similar to the high-energy branch endstation, the low-energy branch will be equipped with a modular endstation, in which ambient pressure X-ray photoelectron spectroscopy as well as near-edge X-ray absorption fine structure and synchrotron IR reflection absorption spectroscopy can be performed in a space- and time-correlated manner. Low-energy branch The second branch ("low energy") is optimized for energies from 20 eV to more than 1000 eV and is dedicated to valence band and soft X-ray spectroscopy, including X-ray absorption spectroscopy at the Li K-edge. [Extracted from the article]

A combined X-band and frequency-domain Fourier-transform THz electron paramagnetic resonance (FD-FT THz-EPR) approach has been employed to determine heme Fe(III)S= 5/2 zero-field splitting (ZFS) parameters of frozen metHb and metMb solutions, both with fluoro and aquo ligands. Frequency-domain EPR measurements have been carried out by an improved synchrotron-based FD-FT THz-EPR spectrometer. ZFS has been determined by field dependence of spin transitions within themS= ±1/2 manifold, for all four protein systems, and by zero-field spin transitions betweenmS= ±1/2 andmS= ±3/2 levels, for metHb and metMb flouro-states. FD-FT THz-EPR data were simulated with a novel numerical routine based onEasyspin, which allows now for direct comparison of EPR spectra in field and frequency domain. We found purely axial ZFSs ofD= 5.0(1) cm−1(flouro-metMb),D= 9.2(4) cm−1(aquo-metMb),D= 5.1(1) cm−1(flouro-metHB) andD= 10.4(2) cm−1(aquo-metHb). [ABSTRACT FROM PUBLISHER]

Aiming at advancing storage-ring-based ultrafast X-ray science, over the past few years many upgrades have been undertaken to continue improving beamline performance and photon flux at the Femtoslicing facility at BESSY II. In this article the particular design upgrade of one of the key optical components, the zone-plate monochromator (ZPM) beamline, is reported. The beamline is devoted to optical pump/soft X-ray probe applications with 100 fs (FWHM) X-ray pulses in the soft X-ray range at variable polarization. A novel approach consisting of an array of nine off-axis reflection zone plates is used for a gapless coverage of the spectral range between 410 and 1333 eV at a designed resolution of E/Δ E = 500 and a pulse elongation of only 30 fs. With the upgrade of the ZPM the following was achieved: a smaller focus, an improved spectral resolution and bandwidth as well as excellent long-term stability. The beamline will enable a new class of ultrafast applications with variable optical excitation wavelength and variable polarization. [ABSTRACT FROM AUTHOR]

The dynamic response of magnetically ordered materials to an ultrashort external stimulus depends on microscopic parameters, such as magnetic moment, exchange, and spin–orbit interactions. Whereas it is well established that, in multicomponent magnetic alloys and compounds, the speed of demagnetization and spin switching processes has an element‐specific character, the magnetization damping was assumed to be a universal parameter for all constituent magnetic elements irrespective of their different spin–orbit couplings and electronic structure. Herein, experimental and theoretical evidence for an element‐specific magnetic damping parameter is provided by investigating the ultrafast magnetization response of a high‐anisotropy ferrimagnetic DyCo5 alloy to femtosecond laser excitation. Strikingly different demagnetization and remagnetization dynamics of Dy and Co magnetic moments is revealed by employing femtosecond laser pump–X‐ray magnetic circular dichroism probe measurements combined with atomistic spin dynamics (ASD) simulations using ab initio calculated parameters. These observations, fully corroborated by the ASD simulations, are linked to the element‐specific spin–orbit coupling strengths of Dy and Co, which are incorporated in the phenomenological magnetization damping parameters. These findings can be used as a recipe for tuning the speed and magnitude of laser‐driven magnetic processes and consequently allow control over various dynamic functionalities in multicomponent magnetic materials. [ABSTRACT FROM AUTHOR]

Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single‐molecule magnets (SMMs). Spin‐phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin‐phonon coupling in molecules is challenging. We have found that far‐IR magnetic spectra (FIRMS) of Co(PPh3)2X2 (Co‐X; X=Cl, Br, I) reveal rarely observed spin‐phonon coupling as avoided crossings between magnetic and u‐symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero‐field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high‐frequency and ‐field EPR (HFEPR), FIRMS, and frequency‐domain FT terahertz EPR (FD‐FT THz‐EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand‐field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co‐X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin‐phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling. [ABSTRACT FROM AUTHOR]

Three new closely related CoIIYIII complexes of general formula [Co(μ-L)(μ-X)Y(NO3)2] (X−=NO3− 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N, N′, N′′-trimethyl- N, N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L). In these complexes, CoII and YIII are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L2−) and one ancillary anion X−. The change of the ancillary bridging group connecting CoII and YIII ions induces small differences in the trigonally distorted CoN3O3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that CoII ions in compounds 1- 3 have large and positive D values (≈50 cm−1), which decrease with increasing the distortion of the pseudo-octahedral CoII coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic ZnII (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that 'hidden single-ion magnet (SIM)' behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K. [ABSTRACT FROM AUTHOR]

The mononuclear complex (Bu4N)2[ReIVCl4(CN)2]·2DMA (DMA = N,N-dimethylacetamide) displays intricate magnetization dynamics, implying Orbach, direct, and Raman-type relaxation processes. The Orbach relaxation process is characterized by an energy barrier of 39 K (27 cm−1) that is discussed based on high-field electron paramagnetic resonance (EPR), inelastic neutron scattering and frequency-domain THz EPR investigations. [ABSTRACT FROM AUTHOR]

The slicing facility FemtoSpeX at BESSY II offers unique opportunities to study photo-induced dynamics on femtosecond time scales by means of X-ray magnetic circular dichroism, resonant and non-resonant X-ray diffraction, and X-ray absorption spectroscopy experiments in the soft X-ray regime. Besides femtosecond X-ray pulses, slicing sources inherently also produce a so-called 'halo' background with a different time structure, polarization and pointing. Here a detailed experimental characterization of the halo radiation is presented, and a method is demonstrated for its correct and unambiguous removal from femtosecond time-resolved data using a special laser triggering scheme as well as analytical models. Examples are given for time-resolved measurements with corresponding halo correction, and errors of the relevant physical quantities caused by either neglecting or by applying a simplified model to describe this background are estimated. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and magnetic properties of four new complex salts, (PPN){[MnIII(salphen)(MeOH)]2[MIII(CN)6]}.7MeOH (Mn2M.7MeOH) (M = Fe, Ru, Os and Co; PPN+ = bis(triphenylphosphoranylidene)ammonium cation; H2salphen = N,N'-bis(salicylidene)-1,2-diaminobenzene), and a mixed metal Co/Os analogue (PPN){[MnIII(salphen)(MeOH)]2[CoIII0.92OsIII0.08(CN)6]}.7MeOH were undertaken. It was found that all compounds exhibit switchable single-molecule magnet (SMM) and exchange-bias behavior depending on the interstitial methanol content. The pristine (PPN){[Mn(salphen)(MeOH)]2[Os(CN)6]}.7MeOH (Mn2Os.7MeOH) behaves as an SMM with an effective barrier for the magnetization reversal, (Ueff/kB), of 17.1 K. Upon desolvation, Mn2Os exhibits an increase of Ueff/kB to 42.0 K and an opening of the hysteresis loop observable at 1.8 K. Mn2Os.7MeOH shows also exchange-bias behavior with magnetic hysteresis loops exhibiting a shift in the quantum tunneling to 0.25 T from zero-field. The FeIII and RuIII analogues were prepared as reference compounds for assessing the effect of the 5d versus 4d and 3d metal ions on the SMM properties. These compounds are also SMMs and exhibit similar effects but with lower energy barriers. These findings underscore the importance of introducing heavy transition elements into SMMs to improve their slow relaxation of the magnetization properties. The (PPN){[MnIII(salphen)(MeOH)]6[CoIII(CN)6]}.7MeOH (Mn2Co.7MeOH) analogue with a diamagnetic CoIII central atom and the mixed Co/Os (PPN){[MnIII(salphen)(MeOH)]2[CoIII0.92OsIII0.08(CN)6]}.7MeOH (Mn6Co/Os.7MeOH) "magnetically diluted" system with a 9:1 Co/Os metal ratio were prepared in order tofurther probe the nature of the energy barrier increase upon desolvation of Mn2Os. In addition, inelastic neutron scattering and frequency-domain Fourier-transform THz electron paramagnetic resonance spectra obtained on Mn2Os.7MeOH and Mn2Os in combination with the magnetic data revealed the presence of anisotropic exchange interactions between MnIII and OsIII ions. [ABSTRACT FROM AUTHOR]

Time-dependent X-ray absorption spectroscopy at the Ge L3edge is used to study the optical switching dynamics of epitaxial phase change materials grown on Si(111) membranes. Small differences between the static absorption spectra of the crystalline and laser-amorphized phase of GeTe are observed. Furthermore, a new approach for pump-probe studies on phase change materials is presented. However, no time-dependent change in the X-ray absorption > 0.1% has been detected so far. This is mainly attributed to sample deterioration at 3 kHz pump-probe rates. [ABSTRACT FROM AUTHOR]

We have investigated the single-molecule magnets [MnIII2(5-Brsalen)2(MeOH)2MIII(CN)6]NEt4 (M=Os ( 1) and Ru ( 2); 5-Brsalen= N, N′-ethylenebis(5-bromosalicylidene)iminate) by frequency-domain Fourier-transform terahertz electron paramagnetic resonance (THz-EPR), inelastic neutron scattering, and superconducting quantum interference device (SQUID) magnetometry. The combination of all three techniques allows for the unambiguous experimental determination of the three-axis anisotropic magnetic exchange coupling between MnIII and RuIII or OsIII ions, respectively. Analysis by means of a spin-Hamiltonian parameterization yields excellent agreement with all experimental data. Furthermore, analytical calculations show that the observed exchange anisotropy is due to the bent geometry encountered in both 1 and 2, whereas a linear geometry would lead to an Ising-type exchange coupling. [ABSTRACT FROM AUTHOR]

Three complexes of Mn(III) with "scorpionate" type ligands have been investigated by a variety of physical techniques. The complexes are [Tp2Mn]SbF6 (1), [Tp2*Mn]-SbF2 (2), and [{PhB(MeIm)3}2Mn](CF3S03) (3a), where Tp- = hydro tris(pyrazolyl)borate anion, Tp*- = hydrotris (3,5-dimethylpyrazolyl)borate anion, and PhB(MeIm)3- = phenyltris(3-methylimidazol-2-yl)borate anion. The crystal structure of 3a is reported; the structures of 1 and 2 have been previously reported, but were reconfirmed in this work. The synthesis and characterization of [{PhB(Melm)³}²Mn]Cl (3b) are also described. These complexes are of interest in that, in contrast to many hexacoordinate (pseudo-octahedral) complexes of Mn(LQ), they exhibit a low-spin (triplet) ground state, rather than the high-spin (quintet) ground state. Solid-state electronic absorption spectroscopy, SQUID magnetometry, and high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy were applied. HFEPR, in particular, was useful in characterizing the S = 1 spin Hamiltonian parameters for complex 1, D = +19.97(1), E = 0.42(2) cm-1, and for 2, D = +15.89(2), E - 0.04(l) cm-1. In addition, frequency domain Fourier-transform THz-EPR spectroscopy, using coherent synchrotron radiation, was applied to 1 only and gave results in good agreement with HFEPR. Variable-temperature dc magnetic susceptibility measurements of I and 2 were also in good agreement with the HFEPR results. This magnitude of zero-field splitting (zfs) is over 4 times larger than that in comparable hexacoordinate Mn(lll) systems with S = 2 ground states. Complexes 3a and 3b (i.e., regardless of counteranion) have a yet much larger magnitude zfs, which may be the result of unquenched orbital angular momentum so that the spin Hamiltonian model is not appropriate. The triplet ground state is rationalized in each complex by ligand-field theory (LFT) and by quantum chemistry theory, both density functional theory and unrestricted Hartree--Fock methods. This analysis also shows that spin-crossover behavior is not thermally accessible for these complexes as solids. The donor properties of the three different scorpionate ligands were further characterized using the LFT model that suggests that the tris (carbene )borate is a strong σ-donor with little or no Π-bonding. [ABSTRACT FROM AUTHOR]

Abstract: We present first concepts for obtaining infrared synchrotron radiation at the Metrology Light Source (MLS), the new low-energy electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute. The MLS is designed in close cooperation with BESSY and will be located adjacent to the BESSY II facility in Berlin. PTB will use the MLS as a dedicated facility for radiometry and photon metrology in the UV and VUV range and as a primary source standard in the VIS/UV and VUV. Furthermore, synchrotron radiation in the IR range will be used. In order to produce coherent synchrotron radiation in the FIR/THz region provision is taken to operate the MLS in a low-alpha machine optics mode. The present design of the three planned infrared beamlines described here will take advantage of the high brightness, the high flux, and the broadband behavior of the synchrotron radiation source. [Copyright &y& Elsevier]

In article number 2100047, Ilie Radu and co-workers provide experimental and theoretical evidence for an element-specific magnetic damping parameter by investigating the ultrafast magnetization response of ferrimagnetic DyCo alloys to femtosecond laser excitation. These novel insights are of utmost importance for understanding the physics of non-equilibrium magnetism as well as for modeling laser-driven magnetic recording phenomena and ultrafast spintronics. Element-Specific Magnetization Damping in Ferrimagnetic DyCo5 Alloys Revealed by Ultrafast X-ray Measurements. [Extracted from the article]

One of the key processes setting the speed of the ultrafast magnetization phenomena is the angular momentum transfer from and into the spin system. However, the way the angular momentum flows during ultrafast demagnetization and magnetization switching phenomena remains elusive so far. We report on time-resolved soft x-ray magnetic circular dichroism measurements of the ferrimagnetic GdFeCo alloy allowing us to record the dynamics of elemental spin and orbital moments at the Fe and Gd sites during femtosecond laser-induced demagnetization. We observe a complete transfer of spin and orbital angular momentum to the lattice during the first hundreds of femtoseconds of the demagnetization process. [ABSTRACT FROM AUTHOR]

By comparing femtosecond laser pulse induced ferro- and antiferromagnetic dynamics in one and the same material--metallic dysprosium--we show both to behave fundamentally different. Antiferromagnetic order is considerably faster and much more efficiently reduced by optical excitation than its ferromagnetic counterpart. We assign the fast and extremely efficient process in the antiferromagnet to an interatomic transfer of angular momentum within the spin system. Our findings imply that this angular momentum transfer channel is effective in other magnetic metals with nonparallel spin alignment. They also point out a possible route towards energy-efficient spin manipulation for magnetic devices. [ABSTRACT FROM AUTHOR]