In general, conventional superconductivity should not occur in a ferromagnet, though it has been seen in iron under pressure. Moreover, theory predicts that the current is always carried by pairs of electrons in a spin singlet state, so conventional superconductivity decays very rapidly when in contact with a ferromagnet, which normally prohibits the existence of singlet pairs. It has been predicted that this rapid spatial decay would not occur if spin triplet superconductivity could be induced in the ferromagnet. Here we report a Josephson supercurrent through the strong ferromagnet CrO2, from which we infer that it is a spin triplet supercurrent. Our experimental set-up is different from those envisaged in the earlier predictions, but we conclude that the underlying physical explanation for our result is a conversion from spin singlet pairs to spin triplets at the interface. The supercurrent can be switched with the direction of the magnetization, analogous to spin valve transistors, and therefore could enable magnetization-controlled Josephson junctions.

We experimentally investigate and quantitatively analyze the spin Hall magnetoresistance effect in ferromagnetic insulator/platinum and ferromagnetic insulator/nonferromagnetic metal/platinum hybrid structures. For the ferromagnetic insulator, we use either yttrium iron garnet, nickel ferrite, or magnetite and for the nonferromagnet, copper or gold. The spin Hall magnetoresistance effect is theoretically ascribed to the combined action of spin Hall and inverse spin Hall effect in the platinum metal top layer. It therefore should characteristically depend upon the orientation of the magnetization in the adjacent ferromagnet and prevail even if an additional, nonferromagnetic metal layer is inserted between Pt and the ferromagnet. Our experimental data corroborate these theoretical conjectures. Using the spin Hall magnetoresistance theory to analyze our data, we extract the spin Hall angle and the spin diffusion length in platinum. For a spin-mixing conductance of 4 × 10 14 −1 m −2 , we obtain a spin Hall angle of 0.11 ± 0.08 and a spin diffusion length of (1.5 ± 0.5) nm for Pt in our thin-film samples.

We demonstrate experimentally the existence of a continuous phase transition between a normal and a true superconductiug phase (with zero linear resistivity) in epitaxial films of Y-Ba-Cu-0 in strong magnetic fields, H&&H, I. The nonlinear I-V curves show scaling behavior near the transition and the relevant critical exponents are extracted. These exponents are consistent with values expected for freezing into a superconducting vortex-glass phase.

Knowledge of the spin polarization is of fundamental importance for the use of a material in spintronics applications. Here, we used femtosecond optical excitation of half-metals to distinguish between half-metallic and metallic properties. Because the direct energy transfer by Elliot-Yafet scattering is blocked in a half-metal, the demagnetization time is a measure for the degree of half-metallicity. We propose that this characteristic enables us vice versa to establish a novel and fast characterization tool for this highly important material class used in spin-electronic devices. The technique has been applied to a variety of materials where the spin polarization at the Fermi level ranges from 45 to 98%: Ni, Co(2)MnSi, Fe(3)O(4), La(0.66)Sr(0.33)MnO(3) and CrO(2).

Monodisperse ternary ferrite (MFe2O4, M = Co, Ni, Mn, and Fe) nanocrystals have been synthesized through a facile and general route involving thermolysis of an intimately mixed binary metal−oleate complex with similar decomposition temperature of the constituents.

Monodisperse wurtzite CuIn(x)Ga(1-x)S(2) nanocrystals have been synthesized over the entire composition range using a facile solution-based method. Depending on the chemical composition and synthesis conditions, the morphology of the nanocrystals can be controlled in the form of bullet-like, rod-like, and tadpole-like shapes. The band gap of the nanocrystals increases linearly with increasing Ga concentration, with band gap values for the end members being close to those observed in the bulk. Colloidal suspensions of the nanocrystals are attractive for use as inks for low-cost fabrication of thin film solar cells by spin or spray coating.

The Raman spectra of epitaxial thin films of La 2 CoMnO 6 on ͑001͒-oriented SrTiO 3 substrates have been measured in several exact scattering configuration between 12 and 890 K. The polarization dependence of the spectra provide clear evidence for ordered P12 1 / n1 structure, differing from its parent Fm3m structure by the presence of rotational distortions. The correlation between the phonon modes in Fm3m, R3, and P12 1 / n1 phases is analyzed and the corresponding types of atomic motions as well as their expected frequency range are determined by comparison to the predictions of lattice dynamical calculations. The ferromagnetic ordering and spin-phonon coupling below T C result in softening of some of the phonon modes. The evolution of the Raman spectra at high temperatures shows no indication for P12 1 / n1-R3 transition up to 800 K.

Superconducting thin films of Y-Ba-Cu oxide have been prepared on yttria-stabilized zirconia substrates using metal trifluoroacetate spin-on precursors. The films exhibit an extremely sharp resistive transition with zero resistance at temperatures as high as 94 K. The superconducting phase is formed by a three-step process: (a) decomposition of the spun-on trifluoroacetate film to the fluorides, (b) conversion of the fluorides to oxides by reacting with water vapor, and (c) annealing followed by slow cooling in oxygen. The properties of the films depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c-axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the film is more randomly oriented and exhibits a broader transition to zero resistance.