As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown1, magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator–metal, or Verwey, transition has long remained inaccessible2, 3, 4, 5, 6, 7, 8. Recently, three-Fe-site lattice distortions called trimerons were identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase9. Here we investigate the Verwey transition with pump–probe X-ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator–metal transition. We find this to be a two-step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5±0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics10

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A collective order of spin and charge degrees of freedom into stripes has been predicted to be a possible ground state of hole-doped Cuo 2 planes, which are the building blocks of hightemperature superconductors. In fact, stripe-like spin and charge order has been observed in various layered cuprate systems. For the prototypical high-temperature superconductor La 2 − x sr x Cuo 4 , no charge-stripe signal has been found so far, but several indications for a proximity to their formation. Here we report the observation of a pronounced charge-stripe signal in the near surface region of 12-percent doped La 2 − x sr x Cuo 4 . We conclude that this compound is sufficiently close to charge stripe formation that small perturbations or reduced dimensionality near the surface can stabilize this order. our finding of different phases in the bulk and near the surface of La 2 − x sr x Cuo 4 should be relevant for the interpretation of data from surface-sensitive probes, which are widely used for La 2 − x sr x Cuo 4 and similar systems.

We report an absolute measurement of the tensor analyzing powers T 20 and T 22 in elastic electrondeuteron scattering at a momentum transfer of 1.6 fm 21 . The novel approach of this measurement is the use of a tensor polarized 2 H target internal to an electron storage ring, with in situ measurement of the polarization of the target gas. Scattered electrons and recoil deuterons were detected in coincidence with two large acceptance nonmagnetic detectors. The techniques demonstrated have broad applicability to further measurements of spin-dependent electron scattering.[ S0031-9007(96) Measurements of spin-dependent electron scattering have the potential to greatly enhance our understanding of nucleon and nuclear structure. For example, spin observables in elastic, quasielastic, and deep-inelastic scattering from polarized deuterium are predicted to provide important information on the effects of D-wave components in the ground state of 2 H [1], the largely unknown charge form factor of the neutron [2], and the neutron spin structure functions [3]. This has prompted development of both polarized 2 H targets for use with internal [4] or external beams [5] and polarimeters for measuring the polarization of recoiling hadrons [6]. Indeed the first round of measurements of spin-dependent e-2 H scattering has been carried out at Novosibirsk [7,8], Bonn [9], MITBates [10,11], and SLAC [12].The measurement of analyzing powers and spincorrelation parameters in spin-dependent electron scattering from polarized nuclei is optimally performed by scattering electrons from a pure and highly polarized target. Polarized internal gas targets in electron storage rings have the advantage that spin-dependent scattering from chemically and isotopically pure atomic species of high polarization can be realized. They offer rapid polarization reversal and flexible orientation of the nuclear spin direction by using low magnetic holding fields, a low thickness at high luminosity which allows for the detection of low-energy recoiling hadrons, and access to a broad kinematic range by using large acceptance detectors. For polarized deuterium one has the additional ability to reverse the tensor polarization, P zz , at fixed vector polarization, P z , and vice versa. Subsequently, small systematic errors can be expected.The first pioneering measurements [7,8] with a polarized deuterium internal target have been carried out at VEPP-3 in Novosibirsk. They realized a target with a thickness limited to about 3 3 10 11 atoms cm 22 [8] as viewed by their detectors. Recently, this was increased by an order of magnitude [13]. Since many mechanisms can depolarize the target nuclei in the storage cell, and no polarimeters were available to measure the target polarization in situ, they normalized one datum to a theoretical prediction, setting the scale for the other data points [8].The electron spin-averaged cross section for elastic electron-deuteron scattering can be expressed [1] as s s 0

We studied the symmetry of the Fe 3d wave function in magnetite below the Verwey temperature T(V) with resonant soft-x-ray diffraction. Although the lattice structure of the low-temperature phase of Fe(3)O(4) is well described by the pseudo-orthorhombic Pmca with a slight monoclinic P2/c distortion, we find that the 3d wave function does not reflect the Pmca symmetry, and its distortion toward monoclinic symmetry is by far larger than that of the lattice. The result supports a scenario in which the Verwey transition involves the ordering of t(2g) orbitals with complex-number coefficients.