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A new aspect of the charge dynamics in layered metallic cuprates has been discovered in the study of the in-plane Hall coefficient (${\mathit{R}}_{\mathit{H}}$) in ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{\mathit{x}}$ over a wide temeprature (4\char21{}500 K) and composition (0x0.35) range. The strongly temperature dependent ${\mathit{R}}_{\mathit{H}}$, a hallmark of cuprate superconductors, is found to be the low temperature part of a simple functional form f(T/${\mathit{T}}^{\mathrm{*}}$) which becomes constant for Tg${\mathit{T}}^{\mathrm{*}}$. This form, followed for x\ensuremath{\ge}0.15, has a characteristic temperature ${\mathit{T}}^{\mathrm{*}}$ which is high at the optimal composition (x=0.15) and decreases with increasing Sr concentration, similar to a temperature scale deduced from magnetic susceptibility.

Most studies of spin caloritronic effects to date, including spin-Seebeck effect, utilize thin films on substrates. We use patterned ferromagnetic thin film to demonstrate the profound effect of a substrate on the spin-dependent thermal transport. With different sample patterns and on varying the direction of temperature gradient, both longitudinal and transverse thermal voltages exhibit asymmetric instead of symmetric spin dependence. This unexpected behavior is due to an out-of-plane temperature gradient imposed by the thermal conduction through the substrate and the mixture of anomalous Nernst effects. Only with substrate-free samples have we determined the intrinsic spin-dependent thermal transport with characteristics and field sensitivity similar to those of the anisotropic magnetoresistance effect.

The in-plane resistivity (ρ ab ) of La 2-x Sr x CuO 4 has been studied over a wide temperature (4-1000 K) and composition range (0 0.2), ρ ab follows a novel power-law dependence, ρ∞T 1.5 , over the entire temperature range up to 1000 K

Bulk-sensitive, polarization-dependent oxygen K- and copper L-edge absorption spectra of single-domain ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ with ${\mathrm{CuO}}_{2}$ planes tilted off the sample surface were measured. A novel experimental configuration was utilized to achieve complete polarization geometry and eliminate optical path variations. Contrary to previous measurements, our data show for both intrinsic and doped holes a significant amount of O2${\mathit{p}}_{\mathit{z}}$ character, likely associated with apical O, but a very weak Cu3${\mathit{d}}_{3\mathit{z}}^{2}$-${\mathit{r}}^{2}$ character. The quantitative results impose strong contraints on superconductivity models invoking out-of-plane orbitals, and suggest that the apical O 2${\mathit{p}}_{\mathit{z}}$ orbital may play an important role in high-${\mathit{T}}_{\mathit{c}}$ phenomena.

We report observation of circular dichroism in reflection from various cuprate superconducting materials, including ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ films, an etched ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ crystal, and a ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ crystal. This signal develops as T is lowered below 200 K and exhibits little change near ${\mathit{T}}_{\mathit{c}}$. The exact onset temperatures differ for the various materials.

In this sytem competing exchange and Zeeman interactions lead to many different possible magnetic structures. Of particular interest is an alternating-helicity phase where the magnetic unit cell is twice the length of the chemical unit cell. A simple theoretical model gives results in good agreement with the experimental measurements

The high-resolution Bitter pattern technique has been used to reveal the magnetic structure of single-crystal samples of high-${T}_{c}$ superconductor Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ at 4.2 K. Typical patterns consist of hexagonally correlated, singly quantized vortices of flux $\frac{\mathrm{hc}}{2e}$. That is, the structures are comparable to those that would be observed in conventional type-II superconductors under similar conditions.

A microscopic magnetic antiphase domain structure has been observed in a single-crystal Gd-Y superlattice by neutron diffraction. Furthermore, this long-range antiferromagnetic correlation is found to occur in a multibilayer, in which each bilayer consists of ${N}_{\mathrm{Gd}}$ ferromagnetic atomic planes of Gd followed by ${N}_{\mathrm{Y}}$ planes of nonmagnetic Y, for ${N}_{\mathrm{Y}}={N}_{\mathrm{Gd}}=10$ but not for ${N}_{\mathrm{Y}}=6 or 20$. This oscillatory behavior is consistent with recent theoretical speculation that the Gd moments are coupled through the intervening Y via the Ruderman-Kittel-Kasuya-Yosida interaction.