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The elastic constants C(11),C(12) and C(44) of U, Np, Pu, and Am telluride single crystals have been obtained by Brillouin scattering from the measured sound velocities in prominent crystallographic directions. In case of the U chalcogenides also by ultrasound techniques. The Cauchy pressure, the Poisson ratio, the anisotropy ratio, the bulk modulus and the Debye temperature have been derived from these data.

U and Pu telluride have a negative C(12) implying intermediate valence. AmTe has a very low bulk modulus, but a positive C(12). It is extremely soft, with a very low sound velocity. For AmTe also the LO and TO phonon frequencies could be determined. The elastic data point to a divalent Am state. The optical reflectivity of the light actinide tellurides (and sometimes of all chalcogenides) has been measured between UV and infrared wavelengths, in the case of AmTe down to the far infrared.

The plasma edge of the free carriers has been determined, which yields the ratio of n/m. Together with the gamma value of the specific heat and magnetic data a consistent proposal for the electronic structure of the light actinide chalcogenides can be given. Thus, the Pu chalcogenides are intermediate valent and represent the high-pressure phase of the corresponding Sm chalcogenides. AmTe, as judged by the electronic, optic and magnetic properties seems to be in the 5f(7) configuration, i.e. divalent Am, but with a narrow, half-filled (24meV) wide 5f band, about 0.1 eV below the bottom of the 6d conduction band. We thus propose a new kind of unhybridized heavy fermion. Also AmTe seems to represent a high-pressure phase of EuTe. Te.

Additional information

Authors: WACHTER P, Laboratorium f³r Festk÷prerphysik, ETH Z³rich (CH);FILZMOSER, Laboratorium f³r Festk÷prerphysik, ETH Z³rich (CH);REBIZANT J, European Institute for Transuranium Elements, Karlsruche (DE)
Bibliographic Reference: An article published in: Physica B (2001) pp.199-223
Availability: An article published in: Physica B (2001) pp.199-223
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