We have performed detailed studies of the structure, magnetotransport, and magnetization Fe/Cr superlattices as a function systematic changes in interfacial roughness. The results clearly show that giant magnetoresistance is enhanced by presence This fact indicates roughness should be explicitly included theoretical calculations experimental characterization exhibiting magnetoresistance.

We present the first direct measurements of ${\mathit{T}}_{\mathit{c}}$ as a function uniaxial stress ${\mathit{p}}_{\mathit{i}}$ (i=a,b,c) along crystal axes for an untwinned ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystal. is linear in with slopes ${\mathit{dT}}_{\mathit{c}}$/${\mathit{dp}}_{\mathit{a}}$=-2.0\ifmmode\pm\else\textpm\fi{}0.2 K/GPa,...

We show clear and conclusive experimental evidence for the enhancement of superconductivity in GdBa2Cu3Ox YBa2Cu3Ox thin films by photoexcitation. Upon laser illumination critical temperature increases while resistivity material decreases. The relaxation back to original state is very slow, order days at room temperature. existence this effect opens possibility fabricating weak-link devices with situ tunable superconducting characteristics.

We show that illumination of oxygen-deficient metallic ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ films produces a change in the Hall coefficient, an increase critical temperature, and decrease electrical resistivity. These changes relax to equilibrium with characteristic times order days, are due variations both carrier density mobility. The relaxation same magnitude as ones measured nonilluminated immediately after quenching.

We have compared the changes in structure and superconductivity of ${\mathrm{Gd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ system produced by rare-earth-ion substitution (chemical pressure) hydrostatic pressure. Although application both chemical physical pressure result an overall compression unit cell, effect on ${\mathit{T}}_{\mathit{c}}$ is opposite sign. A...

We have developed a method for the growth of epitaxial high Tc superconducting thin films with roughness smaller than one unit cell using conventional magnetron sputtering. In this substrate is positioned above edge target (off axis) to avoid resputtering, and oscillated back forth between two symmetrical edges improve film thickness homogeneity. Finite size peaks in x-ray diffraction spectra GdBa2Cu3O7−δ satellite on GdBa2Cu3O7−δ/YBa2Cu3O7−δ superlattice show excellent control smoothness...

We have determined the structure of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ and ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$/${\mathrm{GdBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ high-${\mathit{T}}_{\mathit{c}}$ superlattices using a novel method to refine from x-ray diffraction spectra. This technique allows quantitative determination disorder in good agreement...

Josephson junctions were photogenerated in underdoped thin films of the YBa2Cu3O6+x family using a near-field scanning optical microscope. The observation effect for separations as large 100 nm between two wires indicates existence an anomalously proximity and shows that insulating material gap junction is readily perturbed into superconducting state. critical current was found to be consistent with conventional relationship. This result appears constrain applicability SO(5) theory explain...

We have investigated the periodic pinning of magnetic flux quanta in thin Nb films with rectangular arrays dots. In this type geometry, a change periodicity and shape minima magnetoresistance occurs for fields exceeding certain threshold value. This has been explained recently terms reconfiguration transition vortex lattice due to an increasing vortex-vortex interaction field. picture dominating elastic energy at high forces form square symmetry rather than being commensurate geometry array....

We found a novel dimensional transition in the vortex lattice of finite-sized superconductor. The low-field dependence (with field applied parallel to film plane) magnetization exhibits two maxima, which signal from one dimensions. In dimension vortices line up along film, and with increasing their arrangement changes into two-dimensional array due competition between vortex-surface vortex-vortex repulsion. Agreement is no adjustable parameter calculations using priori known surface-barrier...

We have investigated the time dependence of magnetic and transport properties ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_{3}$ films bulk samples. A significant aftereffect has been observed in all samples through magnetization resistivity measurements. The relaxation effects can be described by addition a logarithmic to an exponential contribution. weight each contribution is strongly temperature dependent, with that predominantly at low temperatures $(T<30 \mathrm{K})$ high...

We have obtained the three uniaxial-pressure derivatives of critical temperature, ${\mathit{T}}_{\mathit{c}}$, for ${\mathrm{GdBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ from hydrostatic pressure dependence measured on films different crystalline orientations. The strain are found to be extremely anisotropic in a-b plane, inducing a decrease (increase) ${\mathit{T}}_{\mathit{c}}$ when compressing across (along) CuO chains. A comparison...

A study of the electromagnetic response superconductor/ferromagnet $\mathrm{Nb}∕\mathrm{Co}$ superlattices is presented. The dc magnetization measured as a function Co layer thickness, applied field ${H}_{a}$, and temperature. For very thin layers, no ferromagnetism detected observed essentially that collection uncoupled Nb layers. When thick enough for to be established, prior field-cooled measurements, layers are magnetically saturated in parallel or antiparallel directions ${H}_{a}$. In...

Raman scattering experiments on oxygen deficient ${\mathrm{GdBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$ thin films ($x=6.53,$ 6.7, 6.8, and 6.93) as a function of photoexcitation annealing induced disorder are presented. lines, unambiguously assigned to copper vibrations involving atoms at the end Cu-O chains, used markers for existence short chain fragments. The dynamics conjunction fragmentation was monitored by peak intensity dependences with time temperature. These results demonstrate...

A sharp temperature- and field-dependent transition from a logarithmic to nonlogarithmic flux-creep behavior has been found in Bi-Sr-Ca-Cu-O superconductors. The is not followed by any noticeable change the magnetization. However, vibrating-reed measurements show that it coincides with strong hardening of magnetic structure. occurs at fields temperatures well below reversibility line. possible relation recently proposed flux lattice melting discussed.

The film thickness (t) dependence of the magnetic properties La0.6Sr0.4MnO3 (LSMO) films grown on (001) MgO and SrTiO3 substrates has been studied. Hysteresis loops measured at low temperature show a smooth increase retentivity accompanied by decrease coercitive field as increases. coercitivity with decreasing t can be interpreted in terms change domain structure mainly due to an augmentation pinning defects. anisotropy using ferromagnetic resonance (FMR). A volume (VA) surface (SA)...

Magnetization measurements in superconductor/ferromagnet Nb/Co superlattices show a complex behavior as function of temperature, applied field and sample history. In base to simple model it is shown that this due an interplay between the superconductor magnetization temperature dependence, ferromagnet time stray fields both materials. It also magnetic state Co layers modified by Nb superconducting response, implying problem superconductor/ferromagnetic heterogeneous has be solved...