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Sereni, J. G., C. Geibel, M. G. Berisso, P. Hellmann, O. Trovarelli, and F. Steglich. "Scaling of the ''C-p proportional to TlnT'' dependence in Ce systems." Physica B – Condensed Matter 230-232 (1997): 580–582.
Abstract: We analyze the T ln T dependence of the specific heat (C-p) in several Ce binaries and ternaries. We find that these systems can be directly compared by using a scaling law of the type: C-p/t = -D log t + ET0, where t = T/T-0, with the scaling temperature T-0 similar to T-K, D = 7.2 J/(mol K) and 0 < E < 0.14 J/(mol K-2). This general function describes those systems within the 0.005 < t < 0.5 range and accounts for nearly 1/2 of the expected entropy of the Ce-doublet.
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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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