High-pressure ground state of SmB6: electronic conduction and long range magnetic order

High-pressure 149Sm nuclear forward scattering of synchrotron radiation and specific heat measurements have been performed on the intermediate valent Kondo insulator SmB6. The results show that at a critical pressure p(c) approximately = 6 GPa, where the charge gap closes, a first order transition occurs to a magnetically ordered state, which shows typical features of trivalent samarium compounds. The similarity with SmS stresses the role of local correlations and gives important insight into the debate on the local or itinerant character of the f electrons in heavy fermion systems.     

Low-energy excitations in polyvinyl chloride: Raman scattering and thermal properties

The low-energy excitations of a very fragile glass-former (in the sense of Angell), poly(vinyl chloride), have been studied by low-frequency Raman scattering and by measurements of the low-temperature heat capacity and thermal conductivity. Two different samples were investigated : one with a crystallinity of about 15%, the other quenched and amorphous, as measured by small-angle neutron scattering. The boson peak in Raman scattering was observed in both samples even at room temperature. A clear correspondance between the Raman boson peak, the excess of heat capacity and the plateau of thermal conductivity was shown. It is confirmed that the boson peak or the heat capacity excess are relatively small in this very fragile glass-former. However it is deduced that the high concentration of tunnelling systems in the amorphous sample is the result of a rapid quenching rather than an intrinsic property of fragile glass-formers.     

Groups in the class semigroups of valuation domains

It is shown that the isomorphy classes of the ideals of a valuation domain form a Clifford semigroup, and the structure of this semigroup is investigated. The group constituents of this Clifford semigroup are exactly the quotients of totally ordered complete abelian groups, modulo dense subgroups. A characterization of these groups is obtained, and some realization results are proved when the skeleton of the totally ordered group is given. The authors are members of GNSAGA of CNR. This research was supported by Ministero dell'Università e della Ricerca Scientifica e Tecnologica, Italy.     

On two-generated modules over valuation domains

Archiv der Mathematik -     

Thermodynamic properties of the gadolinium gallium garnet, Gd3Ga5O12, between 0.05 and 25 K

The specific heat, the entropy, the thermal conductivity and the diffusivity of Gd₃Ga₅O₁₂ have been measured in the presence of an applied magnetic field. Calculations have been performed in order to explain simultaneously all these results within the framework of a simple molecular field theory. The agreement is good above 5 K and at low temperatures the deviations may be explained by the limitations of the simple model.