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Aragón Sánchez, J., R. Cortés Maldonado, M. I. Dolz, N. R. CejasBolecek, C. J. van der Beek, M. Konczykowski, and Y. Fasano. "Direct visualization of local interaction forces in Bi2Sr2CaCu2O8+δ vortex matter." Materials Today: Proceedings 14 (2019): 34–37.
Abstract: We study the local vortex-vortex interaction force fi of the structure frozen during a field-cooling process in an electron-irradiated Bi2Sr2CaCu2O8+δ sample. We compute this magnitude from snapshots of the vortex structure obtained via magnetic decoration experiments at various fields H in the same sample. Since the observed structures correspond to the equilibrium ones frozen at T∼Tirr(H)[1], at this temperature the local modulus of fi roughly equals the local pinning force at the decorated surface of the sample. We estimate the most probable local pinning force from the mode value of the fi(r)distribution, fpm. We found that fpm grows algebraically with H and in electron-irradiated samples is 50-20% smaller than for samples with columnar defects.
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del Corro, P. G., M. Imboden, D. J. Bishop, and H. Pastoriza. "Comb Drive Designs With Minimized Levitation." Journal of Microelectromechanical Systems 25, no. 6 (2016): 1025–1032.
Abstract: This paper presents two capacitive comb drive
designs for electrostatic actuation of MEMS with the aim to
eliminate the levitation effect often observed in such systems.
By placing a shield over the comb drive fingers, it is possible
to balance the electric field and suppress vertical forces while
maintaining the desired lateral motion. By optimizing the comb
geometry, we demonstrate that our approach is able to reduce the
levitation by an order of magnitude and unwanted coupling of
motion from out-of-plane to in-plane by a factor of 7 compared
with standard comb architectures fabricated using PolyMUMPs
technology, without the need of alternating comb finger polarities
or additional control electrodes. Levitation was reduced to
160 nm, for 3.6-µm lateral displacement at a driving voltage
of 80 V.
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Franco, D. G., R. E. Carbonio, and G. Nieva. "Change in the Magnetic Domain Alignment Process at the Onset of a Frustrated Magnetic State in Ferrimagnetic La2Ni(Ni1/3Sb2/3)O6 Double Perovskite." IEEE Transactions on Magnetics 49, no. 8 (2013): 4656–4659.
Abstract: We have performed a combined study of magnetization hysteresis loops and time dependence of the magnetization in a broad temperature range for the ferrimagnetic La2Ni(Ni1/3Sb2/3)O6 double perovskite. This material has a ferrimagnetic order transition at ~100 K and at lower temperatures (~20 K) shows the signature of a frustrated state due to the presence of two competing magnetic exchange interactions. The temperature dependence of the coercive field shows an important upturn below the point where the frustrated state sets in. The use of hysteresis data, magnetization versus applied magnetic field, together with the magnetization versus time data provides a unique opportunity to distinguish between different scenarios for the low temperature regime. From our analysis, a strong domain wall pinning results in the best scenario for the low temperature regime. For temperatures larger than 20 K, the adequate scenario seems to correspond to a weak domain wall pinning.
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Herbsommer, J. A., J. Luzuriaga, L. Civale, G. Nieva, G. Pasquini, H. Lanza, and P. Levy. "Angular variation of pinning near the irreversibility temperature in single crystal Y Ba2Cu3O7-? with splayed columnar defects." Physica C 304, no. 1-2 (1998): 112–118.
Abstract: We have studied vortex pinning through ac susceptibility measurements in single crystals of YBCO with columnar defects (CDs). The CDs have 0, 10 and 20 splay angle and average direction 108 off the c-axis. By studying the angular variation we can compensate for the anisotropy and effects of twins, etc. Using a simple expression we can obtain the angular spread when the field direction is outside the splay angle. An increase of pinning when the field direction is inside
the angle defined by the CDs can be attributed to vortex entanglement due to the splay and the suppression of the sliding of double kinks.
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Luzuriaga, J., M. - O. Andre, and W. Benoit. "Frequency and amplitude response of the flux-line lattice to mechanical perturbation in ceramic YBa2Cu3O7." Physica C: Superconductivity and its applications 201, no. 3-4 (1992): 257–262.
Abstract: The mechanical response of the flux-line lattice has been measured with a low-frequency forced pendulum in ceramic YBa2Cu3O7. A dissipation peak observed in temperature sweeps is frequency-independent between 1 mHz and 5 Hz. Dissipation depends strongly on applied torque, and for fixed temperatures this dependence is well fitted by a rheological model of extended dry friction. If the model is extended to take account of thermal activation, however, it does not agree with the measured frequency independence, which is hard to explain within simple models of thermal activation.
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Luzuriaga, J., C. D'Ovidio, and F. de la Cruz. "Ideal two dimensional flux pinning induced by annealing in superconducting amorphous Zr75Rh25." Solid State Communications 57, no. 9 (1986): 753–756.
Abstract: By annealing amorphous Zr75Rh25 prepared by melt spinning an ideal behaviour of the critical current was observed, in which the measured pinning forces are seen to follow the two dimensional Larkin-Orchivnikov theory. In the region where this theory is valid the changes in the pinning forces can be explained by the changes in the superconducting matrix and it can be assumed that the pinning centers do not change with the heat treatment.
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Osquiguil, E., V. L. P. Frank, and F. de la Cruz. "Two dimensional collective flux pinning in melt spun superconducting amorphous Zr70Cu30." Solid State Communications 55, no. 3 (1985): 227–230.
Abstract: We have measured the critical currents in melt spun amorphous Zr70Cu30 and their evolution with heat treatment. We found that the pinning forces may be interpreted in terms of the Larkin-Ovchinnikov two dimensional collective pinning theory.
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Sirena, M., E. Kaul, M. B. Pedreros, C. A. Rodriguez, J. Guimpel, and L. B. Steren. "Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers." Journal of Applied Physics 109, no. 12 (2011): 123920.
Abstract: The La0.75Sr0.25MnO3 (LSMO)/Ba0.7Sr0.3TiO3 (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample’s magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions.
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