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The surface-boundary magnetization $({M}_{\mathrm{SB}})$ for a manganese perovskite ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ has been investigated using spin-resolved photoemission spectroscopy, which has an $\ensuremath{\sim}5\AA{}$ probing depth. ${M}_{\mathrm{SB}}$ shows the full moment at very low temperature but decays much faster than the bulk magnetization $({M}_{B})$ upon heating. This result provides direct insight into various novel properties at grain and surface boundaries observed in the polycrystalline samples and junctions of manganese perovskites.

The optical properties of N${\mathrm{d}}_{0.7}$S${\mathrm{r}}_{0.3}$Mn${\mathrm{O}}_{3}$ thin films have been studied over a broad spectral range, at temperatures down to 15 K and magnetic fields up to 8.9 T. A large transfer of spectral weight from high energy to low energy occurs as this material is cooled into the ferromagnetic phase, or as the magnetic field is increased near the phase boundary. The optical data are found to be consistent with models that include both the double-exchange interaction and the dynamic Jahn-Teller effect on the ${\mathrm{Mn}}^{3+}$ ${e}_{g}$ levels.

Superlattices of one-unit-cell-thick YBa 2 Cu 3 O 7-δ layers with (Pr x Y 1-x )Ba 2 Cu 3 O 7-δ were fabricated as a model system to study the effects of magnetic coupling on flux pinning in high-T c superconductors. The sample can be transformed from an S/S' to an S/N structure by increasing the temperature from below to above the T c of the intercalating (Pr x Y 1-x )Ba 2 Cu 3 O 7-δ layer. Dramatic changes in the characteristics of the magnetic field and angle dependence of the critical current density caused by a 3D to 2D crossover were observed

The hole-density dependence of the normal-state resistivity and transition temperature ${\mathit{T}}_{\mathit{c}}$ of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ was studied using the electric field effect in ultrathin films of 1 to 8 unit cells thickness. The change in resistivity was found to be equal to the field-induced variation in the areal carrier density, leading to a relation that the conductivity is proportional to the hole density. A similar linear dependence was also found in ${\mathit{T}}_{\mathit{c}}$. However, a saturation occurred in both cases but at different hole densities. The result reveals different effects of hole filling in influencing normal-state and superconducting transport of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$.

Ultrafast picosecond measurements of optically induced changes in the absolute conductivity (0.4–1.0 THz) of La0.7M0.3MnO3 thin films (M Ca, Sr) from 10 K to 0.9Tc reveal a two-component relaxation. A fast, 2 ps, conductivity decrease arises from an optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. We show that, for T o Tc, ≠s≠T is primarily determined by thermally disordered phonons while spin fluctuations dominate near Tc. The observation of “colossal” negative magnetoresistance (CMR) in the hole-doped manganite perovskites (R12xDxMnO3, where, e.g., R La, Nd and D Ca, Sr) demonstrates the sensitivity of electronic conduction to the underlying magnetic structure in these materials [1,2]. Experimental and theoretical work has also revealed the importance of the lattice and orbital degrees of freedom in determining the electronic properties of CMR materials above and below Tc [3,4]. Nonetheless, it is still not clear, especially for T o Tc, what the relative importance of phonons is in comparison to double exchange in determining s. Ultrafast optical spectroscopy has provided significant insight into electron dynamics in metals [5–7], and more recently, transition metal oxides [8 –10]. Using similar ultrafast techniques, we address the relative contributions of spin fluctuations and phonons in determining the conductivity in the manganites from 10 Kt o0.9Tc. Terahertz time-domain spectroscopy is an ultrafast optical technique in which electric field transients are used to measure the complex conductivity of a material. Since this is a coherent technique, a sample can be optically excited and then probed with a terahertz (THz) pulse to measure induced conductivity changes with picosecond (ps) resolution. We use this method, known as timeresolved terahertz spectroscopy (TRTS), to measure ps conductivity transients in La0.7Ca0.3MnO3 (LCMO) and La0.7Sr0.3MnO3 (LSMO) thin films. The dynamics occur on two time scales. A fast, 2 ps, conductivity decrease arises from optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. Our results demonstrate that, at low temperatures, ≠s≠T is primarily determined by thermally disordered phonons while spin fluctuations dominate close to Tc. The TRTS experiments were performed on LCMO and LSMO epitaxial thin films grown on LaAlO3 substrates using pulsed laser deposition [11]. For very thin films (150 A), island growth can alter the film properties, but the thicker films used in these experiments (1000 A) display bulk behavior [12]. Magnetization measurements