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The fundamental and third-harmonic susceptibility response of YBa2Cu3O7−δ (YBCO) and TlBa2Ca2Cu3O10−y (Tl:1223) high-critical temperature (Tc) superconductors with preferentially oriented crystallites has been measured in various magnetic fields up to 14 T, and with very low ac field amplitude, to probe the melting transition of the vortex matter. This method does not require large single crystals, being therefore suitable for high-Tc superconductors with small crystallites, prepared with high-pressure synthesis techniques. We determine experimentally the melting line of vortices and the anisotropy factor in high-pressure-grown Tl:1223 with a high Tc of 133.5 K. Results from similar measurements on YBCO with preferentially oriented grains are consistent with both commonly accepted models of the melting line and values of the anisotropy factor, supporting the validity of our approach.

From frequency-dependent ac susceptibility studies of (Cu,T1)BaSrCa2Cu3Oy superconducting thin films, with and without nanodot-induced artificial pinning centers, we estimated the activation energy of flux jumps. The result was that, in the film with nanodots, the pinning potential is several times higher, leading to a probability of thermally activated flux jumps several orders of magnitude lower than in the film without artificial pinning centers. We suggest that our no cost straightforward method for creating extended defects can be successfully employed for the reduction of thermal noise in superconducting electronic devices.

We have systematically investigated the channel mobility of the 4H-SiC MOSFETs with surface and buried channels in different directions on Si-, a-, and m-faces. We have found that, on a- and m-faces, the in-plane anisotropy of the surface channel mobility is different from that of the buried channel mobility. It has been demonstrated that this anomalous anisotropic behavior can be observed regardless of the gate oxide processes. These results suggest that the dependence of scattering mechanisms or effective masses of carriers on crystal orientations may be modulated near the oxide/SiC interface.

We report synthesis and properties of the simplest double-layered cuprate superconductor Ba2CaCu2O4(O,F)2. A superconducting transition temperature (Tc) has been achieved as high as 108K for a sample with a nominal fluorine content y=1.6 in Ba2CaCu2O6−yFy. The Tc is the highest among double-layer cuprates that are free of toxic elements such as Hg, Tl, and Pb so that the nontoxic Ba2CaCu2O4(O,F)2 will be promising for application. As y decreases from approximately 2, the a-axis length decreases and the Tc increases from 40to108K. The material is underdoped at large y and as y decreases, the doping moves toward an optimally doped state.