Fivos Drymiotis

TUNABLE THERMAL EXPANSION BEHAVIOR IN THE INTERMETALLIC YBGAGE

We investigate the effects of carbon and boron doping on the thermal expansion of the hexagonal (P6{sub 3}/mmc) intermetallic YbGaGe. X-ray powder diffraction was used to measure the lattice constants on pure and doped (C or B at nominal levels of 0.5%) samples from T{approx}10 K to T{approx}300 K. Also measured were resistivity, specific heat, and magnetic susceptibility. While the pure YbGaGe samples exhibit positive thermal volume expansion (V{sub 300K}-V{sub 10K})/V{sub 300K}=0.94, the volume expansion in the lightly C- or B-doped samples changes slope and tends toward zero-volume expansion. Such a strong response to light doping suggests that the underlying mechanism for the reported zero-volume expansion is substitutional disorder, and not the previously proposed valence fluctuations.

Physical properties of the β-Ti6Sn5 system

The current work reports the specific heat, the resistivity and the magnetic susceptibility of both single-crystal and polycrystalline β-Ti6Sn5 at cryogenic temperatures. The effects of small additions of magnetic and non-magnetic impurities were examined. Resistivity and magnetic susceptibility measurements reveal that the undoped material is a Pauli paramagnet displaying Fermi-liquid behaviour, while ferromagnetic ordering was observed at T150K with small additions of Ce, La or Co. Analysis of the electronic specific heat γ and magnetic susceptibility gives an unexpectedly large Wilson ratio R w of 1.76, a value indicative of correlated electron behaviour. We present the general physical properties and based on the sensitivity of the magnetic properties to doping, show evidence that β-Ti6Sn5 exhibits a ground state in close proximity to a non-magnetic and magnetic phase boundary.

Suppression of the γ–α structural phase transition in Ce0.8La0.1Th0.1 by large magnetic fields

The γ –α transition in Ce0.8La0.1Th0.1 is measured as a function of applied magnetic field using both resistivity and magnetization. The γ –α transition temperature decreases with increasing magnetic field, reaching zero temperature at around 56 T. The magnetic-field dependence of the transition temperature is quantitatively reproduced by a model that invokes the field and temperature dependence of the entropy of the 4f-electron moments of the γ phase. (Some figures in this article are in colour only in the electronic version)

Suppression of the γ-α structural phase transition in Ce0.8La0.1Th0.1by large magnetic fields

The γ –α transition in Ce0.8La0.1Th0.1 is measured as a function of applied magnetic field using both resistivity and magnetization. The γ –α transition temperature decreases with increasing magnetic field, reaching zero temperature at around 56 T. The magnetic-field dependence of the transition temperature is quantitatively reproduced by a model that invokes the field and temperature dependence of the entropy of the 4f-electron moments of the γ phase. (Some figures in this article are in colour only in the electronic version)