Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3O6.54 at its superconducting transition temperature ∼60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.

Microscopic structural instabilities of EuTiO3 single crystal were investigated by synchrotron x-ray diffraction. Antiferrodistortive (AFD) oxygen octahedral rotational order was observed alongside Ti derived antiferroelectric (AFE) distortions. The competition between the two instabilities is reconciled through a cooperatively modulated structure allowing both to coexist. The combination of electric and magnetic fields on the modulated AFD order shows that the origin of the large magnetoelectric coupling is based upon the dynamic equilibrium between the AFD -antiferromagnetic interactions versus the electric polarization -ferromagnetic interactions.

We identify and investigate thermal spin transport phenomena in sputter-deposited Pt/NiFe2O4-x (4 ≥ x ≥ 0) bilayers. We separate the voltage generated by the spin Seebeck effect from the anomalous Nernst effect contributions and even disentangle the intrinsic anomalous Nernst effect (ANE) in the ferromagnet (FM) from the ANE produced by the Pt that is spin polarized due to its proximity to the FM. Further, we probe the dependence of these effects on the electrical conductivity and the band gap energy of the FM film varying from nearly insulating NiFe2O4 to metallic Ni33Fe67. A proximity-induced ANE could only be identified in the metallic Pt/Ni33Fe67 bilayer in contrast to Pt/NiFe2Ox (x > 0) samples. This is verified by the investigation of static magnetic proximity effects via x-ray resonant magnetic reflectivity.In the emerging fields of spintronics Pt is employed frequently for generating and detecting pure spin currents, if adjacent to an FMI, although the possibility of magnetic proximity effects (MPEs) has to be taken into account. Due to its close vicinity to the Stoner criterion [11] the FM can potentially generate a Pt spin polarization at the interface. Consequently, this might induce additional parasitic effects preventing the correct interpretation of the measured ISHE voltage. Therefore, a comprehensive investigation regarding the magnetic properties of the NM/FM interface is required to distinguish the contributions of such parasitic voltages from the ISHE voltage generated by a pure spin current.In the case of SSE, the driving force for the spin current in the FM or FMI is a temperature gradient. When a spin current is generated parallel to a temperature gradient, it is generally attributed to the longitudinal spin Seebeck effect (LSSE) [4,5]. However, when using the ISHE in an adjacent NM for the spin current detection, not only a proximity-induced ANE [12] can contaminate the LSSE signal, but also an additional intrinsic ANE contribution could be present in case of studying ferromagnetic metals (FMMs) or semiconducting ferro(i)magnets [13,14]. Mainly NM/FMI bilayers have been investigated, while LSSE studies on NM/FMM are quite rare.However, Ramos et al. [14][15][16][17] and Wu et al. [18] individually investigated the LSSE in magnetite, which is conducting at room temperature (RT) and, thus, has an intrinsic ANE contribution. They identified the LSSE in Pt/Fe 3 O 4 [14] and CoFeB/Fe 3 O 4 bilayers [18] by using temperatures below the conductor-insulator transition of magnetite (Verwey transition at 120 K) in order to exclude any intrinsic ANE contribution. Ramos et al. further investigated the ANE in bulk magnetite without any Pt [15] and concluded that the ANE contributions for Pt/Fe 3 O 4 bilayers and multilayers should be quite small [16,17]. In addition, Lee et al. [19] and Uchida et al. [20,21] discussed that in Pt/FMM multilayers both LSSE and ANE contribute, but did not disentangle the effects quantitatively. Hence, a clear quantitative disentanglement of the LSSE in the FMM [22], the ...

The beamline, which is situated on a bending magnet at ESRF, comprises a unique combination of instrumentation for high-resolution and magnetic single-crystal diffraction. White-beam operation is possible, as well as focused and unfocused monochromatic modes. In addition to an eleven-axis Huber diffractometer, which facilitates simple operation in both vertical and horizontal scattering geometries, there is an in-vacuum polarization analyser and slit system, mirrors for harmonic rejection, sub 4.2 K and 1 Tesla magnetic field sample environment, plus a diamond phase plate for polarization conditioning. The instrumentation developed specifically for this beamline is described, and its use illustrated by recent scientific results.

Intrinsic magnetoelectric coupling describes the interaction between magnetic and electric polarization through an inherent microscopic mechanism in a single-phase material. This phenomenon has the potential to control the magnetic state of a material with an electric field, an enticing prospect for device engineering. Here, we demonstrate 'giant' magnetoelectric cross-field control in a tetravalent titanate film. In bulk form, EuTiO 3 , is antiferromagnetic. However, both anti and ferromagnetic interactions coexist between different nearest europium neighbours. In thin epitaxial films, strain was used to alter the relative strength of the magnetic exchange constants. We not only show that moderate biaxial compression precipitates local magnetic competition, but also demonstrate that the application of an electric field at this strain condition switches the magnetic ground state. Using first-principles density functional theory, we resolve the underlying microscopic mechanism resulting in G-type magnetic order and illustrate how it is responsible for the 'giant' magnetoelectric effect.

Using high-resolution x-ray scattering, we have demonstrated the existence of quenched disordered charge stripes in a single crystal of La (5/3)Sr (1/3)NiO (4) at low temperatures. Above the second-order transition critical scattering was observed due to fluctuations into the charge stripe phase. The charge stripes are shown to be two dimensional in nature both by measurements of their correlation lengths (xi(a) approximately 185 A, xi(b) = 400 A, and xi(c) approximately 25 A) and by the critical exponents of the charge strip transition. The charge stripe ordering did not develop long-range order even at low temperatures, indicating that the charge stripes are disordered and that the length scale of the disorder is quenched.

X-ray resonant magnetic scattering studies of rare-earth magnetic ordering were performed on perovskite manganites RMnO 3 ͑R =Dy,Gd͒ in an applied magnetic field. The data reveal that the field-induced threefold polarization enhancement for H ʈ a͑H Ϸ 20 kOe͒ observed in DyMnO 3 below 6.5 K is due to a re-emergence of the Mn-induced Dy spin order with propagation vector Dy = Mn = 0.385b ‫ء‬ , which accompanies the suppression of the independent Dy magnetic ordering, Dy =1/ 2b ‫ء‬ . For GdMnO 3 , the Mn-induced ordering of Gd spins is used to track the Mn-ordering propagation vector. The data confirm the incommensurate ordering reported previously, with Mn varying from 0.245b ‫ء‬ to 0.16b ‫ء‬ on cooling from T N Mn down to a transition temperature TЈ.New superstructure reflections which appear below TЈ suggest a propagation vector Mn =1/ 4b ‫ء‬ in zero magnetic field, which may coexist with the previously reported A-type ordering of Mn. The Gd spins order with the same propagation vector below 7 K. Within the ordered state of Gd at T = 1.8 K we find a phase boundary for an applied magnetic field H ʈ b, H = 10 kOe, which coincides with the previously reported transition between the ground-state paraelectric and the ferroelectric phases of GdMnO 3 . Our results suggest that the magnetic ordering of Gd in magnetic field may stabilize a cycloidal ordering of Mn that, in turn, produces ferroelectricity.

In-situ grazing incidence X-ray diffraction has been used to investigate the kinetics of crystallization at the surface of thin films of poly(ethylene terephthalate) (PET). By varying the angle of incidence of the X-ray beam around the critical angle of the film, the penetration depth can be tuned to allow a direct comparison of molecular ordering in the surface and bulk of the film. The results show that ordering occurs significantly faster at the surface in the temperature range 90−100 °C (close to the bulk glass transition temperature of 75 °C). The (0 1̄ 1) and (0 1 0) peaks narrow more rapidly and achieve a lower width, indicating that the crystallization progresses more rapidly in these crystallographic directions. This enhanced ordering is attributed to a combination of surface energy effects, which promote localized packing, and to an enhanced segmental mobility near the free surface.