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Trovarelli, O., J. G. Sereni, and J. P. Kappler. "Role of Ce sublattices in the thermal and magnetic properties of Ce7X3 (X=Ni, Ru, Rh, Ir, Pd, and Pt) compounds." Journal of Low Temperature Physics 108, no. 1-2 (1997): 53–85.
Abstract: The role of the Ce sublattices in the thermal and magnetic properties of the Ce7X3 (X = Ni, Ru, Rh, Ir, Pd, and Pt) family of compounds is studied by means of ac and dc magnetic susceptibility, mngnetization and mainly specific-heat experiments in applied magnetic field. The experimental data show that in these compounds there is coexistence of magnetic order, heavy-fermion and intermediate-valence behavior, which is interpreted in terms of the contribution of the three different sublattices present in the crystalline structure of Th7Fe3-type (denoted by 1Ce(I), 3Ce(II) and 3Ce(III)). From the available volume of the Ce-III atoms in their crystallographic environment it is found that sublattice Ce-III has an intermediate-valence behavior, whereas from entropic considerations sublattices Ce-I and Ce-II are identified as responsible for the magnetic order or heavy-fermion behavior, depending on the Ce-ligand electronic structure. This systematics evidences a clear correlation between the thermal and magnetic properties of these compounds and the position of the respective Ce-ligands in the periodic table, through the particular sensitivity of Ce to the environmental conditions.
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Pardo, Flavio. "Estructura estática y dinámica de la red de vórtices : decoración magnética y otras técnicas experimentales." (1997).
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Goffman, Marcelo F. "Vórtices en superconductores laminares de alta temperatura crítica." Ph.D. thesis, , 1997.
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Pardo, F., A. P. Mackenzie, F. delaCruz, and J. Guimpel. "Effect of the reversibility region on the low-temperature vortex structure imaged by Bitter magnetic decoration." PHYSICAL REVIEW B 55, no. 21 (1997): 14610–14613.
Abstract: We have combined magnetic measurements and imaging of the vortex lattice at low fields in Tl2Ba2CuO6-delta single crystals with different oxygen content. Those with high critical temperature T-c > 80 K have a reversible region while those with low T-c < 30 K have an irreversible magnetization in the whole range of temperatures, up to T-c. The presence of the reversible region allows the formation of ordered vortex structures, while amorphous structures are obtained when no reversible region is present below T-c. The results are discussed in terms of vortex nucleation processes in the individual pinning regime.
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Weiden, M., R. Hauptmann, W. Richter, C. Geibel, P. Hellmann, M. Koppen, F. Steglich, M. Fischer, P. Lemmens, G. Guntherodt et al. "Magnetic phase diagram of CuGe1-xSixO3." PHYSICAL REVIEW B 55, no. 22 (1997): 15067–15075.
Abstract: The effect of Si doping on the magnetic properties of the spin-Peierls (SP) system CuGeO3 was found to differ strongly between polycrystals (PC's) and single crystals (SC's). In SC's, the SP state is suppressed much mon strongly, whereas the existence region of the antiferromagnetic (AF) state is enhanced. We investigated the origin of this difference by means of magnetic susceptibility, specific heat, thermal expansion, Raman scattering, elastic neutron scattering, and x-ray measurements on CuGe1-xSixO3 samples prepared under different conditions. The partial oxygen pressure and the temperature during the synthesis were found to have a profound influence on the magnetic properties: preparation under reduced oxygen pressure leads to a stabilization of the AF state, whereas heating above the melting point results in a strong decrease of T-SP in Si-doped samples. Therefore, both the AF stabilization and the TSP reduction observed in SC's are not an intrinsic effect of Si doping PC samples, which can be prepared at lower temperatures and more oxidizing conditions, reflect much better the intrinsic properties of CuGe1-xSixO3. We were able to prepare PC samples up to 50 at. % Si and found a continuous decrease of the one-dimensional character of the magnetic properties without pronounced changes in the structure.
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Righi, E. F., S. A. Grigera, G. Nieva, D. Lopez, and F. delaCruz. "Finite vortex correlation in the c direction in YBa2Cu3O7-delta above the first-order melting transition." PHYSICAL REVIEW B 55, no. 21 (1997): 14156–14159.
Abstract: The in- and out-of-plane resistivities of untwinned YBa2Cu3O7-delta show that at the melting temperature of the vortex lattice T-m(H), the c-axis vortex correlation length has a finite value, demonstrating that the first-order transition is a true melting and not a decoupling transition. The vortex liquid just above T-m(H) has a correlation length in the field direction on the order of a micron. The in-plane I-V characteristics in the liquid state show non-Ohmic behavior, providing evidence that thermal fluctuations dominate the response even at the first-order transition.
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Righi, E. F., S. A. Grigera, D. Lopez, G. Nieva, F. delaCruz, L. Civale, G. Pasquini, and P. Levy. "Enhancement of c-axis vortex correlation by twin boundaries and columnar defects in YBa2Cu3O7-delta." PHYSICAL REVIEW B 55, no. 9 (1997): 5663–5665.
Abstract: We report on transport measurements using the flux transformer configuration in a twinned single crystal of YBa2Cu3O7-delta with columnar defects. The vortex liquid shows velocity correlation along the c axis (the direction of the applied magnetic field and the columnar defects) at temperatures that correspond to an uncorrelated liquid in unirradiated samples of the same thickness. These results and previous work about the effect of twin boundaries on vortex velocity correlation show that phase coherence in the field direction is not an intrinsic property of vortex liquids but one induced by extended defects.
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