Sereni, J. G., G. Nieva, J. G. Huber, E. Braun, F. Oster, E. Bruck, B. Roden, and D. Wohlleben. "Evidence for 4f-instability of dilute terbium in thorium." Journal of Magnetism and Magnetic Materials 63-64 (1987): 597–599.
Abstract: We have measured the specific heat of dilute Th1?xTbx alloys (0.44 < x < 2.15 a/o), which rises linearly between 0.4 and 0.9 K with a slope of ?C/T ? 450 mJ/K2molTb followed by a Schottky anomaly with a maximum near 3.8 K. The high temperature ??T product was found to be 4% lower than that of Tb3+. The resistivity shows no minimum at low temperatures. Discussion is made in terms of non-integral valence of Tb.
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SERENI, J. G. "The role of “p-like†orbitals in Ce valence instabilities." Journal of Magnetism and Magnetic Materials 47-48, no. FEB (1985): 228–230.
Abstract: From the analysis of spectroscopical data of atomic Ce, the [f(dsp)] configuration is found to be the least energetic when the metallization enthalpy is taken into account. The p-character of the band in Ce IV compounds is discussed and the p-f hybridization proposed.
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Pureur, P., G. L. Fraga, D. E. Brandao, R. Caudron, H. Safa, and G. Nieva. "Specific heat measurements in scandium-rare earth anisotropic spin glasses." Journal of Magnetism and Magnetic Materials 68, no. 2 (1987): 213–217.
Abstract: We report on specific heat measurements at low temperature of the anisotropic spin glass alloys ScDy 3 at%, ScEr 4.25 at% and ScEr 10 at%. We find that at the lowest temperature range the data indicate the occurrence of an anisotropy induced gap around zero frequency in the density of states of the magnetic excitations. Moreover, some of our specific heat curves present a maximum coinciding with Tg, raising thus the question of thermal signs for a spin glass phase transition in anisotropic systems.
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Franco, D. G., R. E. Carbonio, E. E. Kaul, and G. Nieva. "Tailoring the ground state of the ferrimagnet La2Ni(Ni1/3Sb2/3)O6." Journal of Magnetism and Magnetic Materials 346 (2013): 196–202.
Abstract: We report on the magnetic and structural properties of La2Ni(Ni1/3Sb2/3)O6 in polycrystal, single crystal and thin film samples. We found that this material is a ferrimagnet ( T c ≈ 100 K ) which possesses a very distinctive and uncommon feature in its virgin curve of the hysteresis loops. We observe that bellow 20 K it lies outside the hysteresis cycle, and this feature was found to be an indication of a microscopically irreversible process possibly involving the interplay of competing antiferromagnetic interactions that hinder the initial movement of domain walls. This initial magnetic state is overcome by applying a temperature dependent characteristic field. Above this field, an isothermal magnetic demagnetization of the samples yield a ground state different from the initial thermally demagnetized one.
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Betancourth, D., J. I. Facio, P. Pedrazzini, C. B. R. Jesus, P. G. Pagliuso, V. Vildosola, P. S. Cornaglia, D. J. García, and V. F. Correa. "Low Temperature magnetic properties of GdCoIn5." Journal of Magnetism and Magnetic Materials 374 (2015): 744–747.
Abstract: A comprehensive experimental and theoretical study of the low temperature properties of GdCoIn5 was performed. Specific heat, thermal expansion, magnetization and electrical resistivity were measured in good quality single crystals down to 4He temperatures. All the experiments show a second-order-like phase transition at 30 K probably associated with the onset of antiferromagnetic order. The magnetic susceptibility shows a pronounced anisotropy below T N with an easy magnetic axis perpendicular to the crystallographic ĉ-axis. Total energy GGA+U calculations indicate a ground state with magnetic moments localized at the Gd ions and allowed a determination of the Gd-Gd magnetic interactions. Band structure calculations of the electron and phonon contributions to the specific heat together with Quantum Monte Carlo calculations of the magnetic contributions show a very good agreement with the experimental data. Comparison between experiment and calculations suggests a significant anharmonic contribution to the specific heat at high temperature (View the MathML sourceT≳100K).
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Facio, J. I., D. Betancourth, N. R. Cejas Bolecek, G. A. Jorge, P. Pedrazzini, V. F. Correa, P. S. Cornaglia, V. Vildosola, and García D.J. "Lattice specific heat for the RMIn5 (R=Gd, La,Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction." Journal of Magnetism and Magnetic Materials 407 (2016): 406–4011.
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