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The spin-phonon interaction in spin density wave (SDW) systems often determines the free energy landscape that drives the evolution of the system. When a passing energy flux, such as photoexcitation, drives a crystalline system far from equilibrium, the resulting lattice displacement generates transient vibrational states. Manipulating intermediate vibrational states in the vicinity of the critical point, where the SDW order parameter changes dramatically, would then allow dynamical control over functional properties. Here we combine double photoexcitation with an X-ray free-electron laser (XFEL) probe to control and detect the lifetime and magnitude of the intermediate vibrational state near the critical point of the SDW in chromium. We apply Landau theory to identify the mechanism of control as a repeated partial quench and sub picosecond recovery of the SDW. Our results showcase the capabilities to influence and monitor quantum states by combining multiple optical photoexcitations with an XFEL probe. They open new avenues for manipulating and researching the behaviour of photoexcited states in charge and spin order systems near the critical point., Precise control of vibrational states coupled to electronic degrees of freedom could enable control over charge or magnetic order in a material. Here, the authors use a double-pulse photoexcitation combined with an X-ray probe to control vibrational states near the critical point of spin density wave in Cr films.

Advanced engineering materials 23(11), 2100201 (2021). doi:10.1002/adem.202100201 special issue: "Neutrons and Synchrotron Radiation - Unique Tools for the Characterization of Materials", The fast and contact-free detection of biomagnetic vital signs can benefit clinical diagnostics in medical care, emergency services, and scientific studies, hugely. A highly sensitive magnetoelectric sensor for the detection of biomagnetic signals combined with the piezotronic effect is a promising path to increase the signal detection limit. Herein, the results of three ZnO microrods examined by nano X-ray diffraction and current���voltage curves to investigate the crystalline structure influence on the Schottky contact properties are presented. The measurements reveal different strain distributions for the three rods and that these are linked with the electrical properties, showing that the crystalline quality has a direct influence on the Schottky contact properties. An analytical model is created to determine the influence of the stress. Although rotation of the strain orientation changes the strain appearance in the measurement, it does not affect the Schottky contact properties., Published by Deutsche Gesellschaft fu��r Materialkunde, Frankfurt, M.

Pump–probe experiments at synchrotrons and free-electron lasers to study ultrafast dynamics in materials far from equilibrium have been well established, but techniques to investigate equilibrium dynamics on the nano- and pico-second timescales remain underdeveloped and experimentally challenging. A promising approach relies on a double-probe X-ray speckle visibility spectroscopy setup at split-and-delay beamlines of X-ray free-electron lasers. However, the logistics in consistently producing two collinear, perfectly overlapping pulses necessary to conduct a faithful experiment is difficult to achieve. In this paper, a method is introduced to extract contrast in the case where an angular misalignment and imperfect overlap exists between the two pulses. Numerical simulations of a dynamical system show that contrast can still be extracted for significant angular misalignments accompanied by partial overlap between the two pulses.

X-ray reflectivity studies of the structure of liquid–vapour and liquid–liquid interfaces at modern sources, such as free-electron lasers, are currently impeded by the lack of dedicated liquid surface diffractometers. It is shown that this obstacle can be overcome by an alternative experimental approach that uses the natural curvature of a liquid drop for variation of the angle of incidence. Two modes of operation are shown: (i) sequential reflectivity measurements by a nanometre beam and (ii) parallel acquisition of large ranges of a reflectivity curve by micrometre beams. The feasibility of the two methods is demonstrated by studies of the Hg/vapour, H2O/vapour and Hg/0.1 MNaF interface. The obtained reflectivity curves match the data obtained by conventional techniques up to 5αcin micro-beam mode and up to 35αcin nano-beam mode, allowing observation of the Hg layering peak.

The intrinsic strain at coupled components in magnetoelectric composites plays an important role for the properties and function of these materials. In this in situ X-ray nanodiffraction experiment, the coating-induced as well as the magnetic-field-induced strain at the coupled interface of complex magnetoelectric microcomposites were investigated. These consist of piezoelectric ZnO microrods coated with an amorphous layer of magnetostrictive (Fe90Co10)78Si12B10. While the intrinsic strain is in the range of 10–4, the magnetic-field-induced strain is within 10–5, one order of magnitude smaller. Additionally, the strain relaxation distance of around 5 μm for both kinds of strain superposes indicating a correlation. The value of both intrinsic and magnetic-field-induced strain can be manipulated by the diameter of the rodlike composite. The intrinsic interface strain within the ZnO increases exponentially by decreasing the rod diameter while the magnetic-field-induced strain increases linearly within the gi...

The elastic coupling in multiferroic materials and even more so in magnetoelectric composites plays an important role for the properties and function. In this study, the electrically induced strain at the epitaxial interface of 0.72Pb(Mn1/3Nb2/3)O3–0.28PbTiO3—CoFe2O4, a magnetoelectric composite, is characterized by in situ X-ray scattering experiment and transmission electron microscopy study. For the measured range all strain induced lattice changes are reversible ruling out plastic deformation. The surprisingly non-perfect elastic coupling of 87 ± 7% in this epitaxial system can be explained by the presence of planar defects in the CFO film.

The microscopic processes underlying magnetostriction in ferrites were studied for the case of $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$ single crystals by high-resolution in situ x-ray diffraction and complementary magnetic microscopy techniques. The data support the reports of Yang and Ren [Phys. Rev. B 77, 014407 (2008)] that magnetostriction in these materials originates from the switching of crystallographic domains, similar to ferroelastic or ferroelectric domain switching, and reveals the presence of two coexisting tetragonal spinel structures, corresponding to domains of high and of low strain. The latter alternate in the crystal, separated by 90\ifmmode^\circ\else\textdegree\fi{} domain boundaries, and can be explained by the effect of internal stress emerging during the transition into the ferrimagnetic phase. During magnetization of the sample two structural transitions are observed: a conversion of the transversal into axial domains at 1.95 kOe and a growth of the high-strain domains at the cost of the low-strain axial domains at 2.8 kOe. These microscopic changes are in good agreement with the macroscopic magnetization and magnetostriction behavior of $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$.

Magneto-optic Kerr effect microscopy and nanofocus X-ray diffraction are combined to investigate the local mapping of the magnetoelectric microcomposite properties of ZnO microrods coated with an amorphous (Fe90Co10)78Si12B10 layer. We follow the magnetic domain behavior and lattice deformation upon applying an external magnetic field. In addition to the expected field induced strain, we observe a local magnetic induced strain in the 10−5 range in the ZnO localized near the (Fe90Co10)78Si12B10 /ZnO interface.

Static and magnetic field induced strains at a magnetoelectric (ME) buried interface, consisting of a ZnO(001) piezoelectric substrate and an amorphous Fe58Tb42 magnetostrictive layer, were determined by measuring the intensity of the forbidden ZnO(3–31) Bragg reflection. The comparison with an uncoated ZnO substrate shows that a permanent strain is induced by the growth process. For FeTb coated ZnO, an additional static strain of (1.6 ± 0.2) × 10−4 relative to the pure ZnO substrate is found near the interface, which is close to that determined from the peak position shift of the allowed ZnO(4–40) Bragg reflection. Upon applying a magnetic field along the [1–10] direction, the intensity of the ZnO(3–31) forbidden Bragg reflection increases with increasing field magnitude as predicted. The induced strain, transferred to the piezoelectric ZnO substrate due to the external magnetic field acting on the magnetostriction FeTb layer, approaches a saturation value of eH = (3.7 ± 0.2) × 10−4 at B ≥ 0.05 T, in goo...

The magnetic field induced strain at the interface of a magnetoelectric composite, consisting of a ZnO(001) piezoelectric substrate and an amorphous (Fe90Co10)78Si12B10 magnetostrictive layer, was directly determined by grazing incidence X-ray diffraction. Upon applying a magnetic field along the [110] direction, the ZnO single crystal is under tensile strain in [110] direction and compressive strain in [1-10] direction, in agreement with the magnetostriction in the (Fe90Co10)78Si12B10 layer. At room temperature, the saturation strain along [1-10] of about 3 × 10−5 is close to the saturation magnetostriction of the film measured with the cantilever bending technique.