Anomalies in Physical Properties Related to the Stability of the B2-Phase in Ti-Ni-Co Shape Memory Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 1977-1982 ◽  
Author(s):  
Mi Seon Choi ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Martensitic Transformation ◽  
Specific Heat ◽  
Nucleation And Growth ◽  
Electronic Specific Heat ◽  
Transformation Behavior ◽  
First Order ◽  
The Stability ◽  
Specific Heat Coefficient

Martensitic transformation behavior of a series of Ti-(50-x)Ni-xCo at% alloys (x = 4, 8, 12, 16, 20) has been examined by electrical resistivity, magnetic susceptibility and specific heat measurements, in order to know the phase stability of the B2-type structure. The 4Co and 8Co alloys exhibit a typical first order B2-R-B19' transformation. The 12Co alloy probably transforms to the R-phase, but its microstructure is composed of small domains with about 10 nm in diameter, being quite different from the microstructure of a typical R-phase formed by nucleation and growth. The 16Co and the 20Co alloys do not show any martensitic transformation but anomalies of the electrical resistivity and magnetic susceptibility being similar to those of the 12Co alloy appear in these alloys. The diffuse scattering of 1/3<110> is also observed in the 16Co alloy. The Debye temperature decreases and electronic specific heat coefficient increases with increasing Co content.

Specific heat below 3 °K of a gold–zinc and a gold–indium alloy

1969 ◽  
Vol 47 (10) ◽  
pp. 1077-1081 ◽  
Author(s):  
Douglas L. Martin
Keyword(s):  
Specific Heat ◽  
Face Centered Cubic ◽  
Electronic Specific Heat ◽  
Confidence Limits ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Atomic Silver ◽  
Face Centered ◽  
Specific Heat Coefficient ◽  
Limiting Value

Face-centered-cubic alloys of gold with 10 atomic % zinc (divalent) and 10 atomic % indium (trivalent), respectively, were measured in the range 0.4 to 3.0 °K. The coefficients of the nuclear specific-heat term were 1.80 ± 0.07 μcal °K/g atom for AuZn and 1.29 ± 0.06 μcal °K/g atom for AuIn (95% confidence limits). For a gold–10 atomic % silver (monovalent) alloy (Martin 1968) the nuclear term was 0.44 μcal °K/g atom. These results show that electric field gradients in alloys are not simply proportional to the valence difference of the components, a conclusion which may be drawn from NMR results. For the AuZn alloy the electronic specific-heat coefficient (γ) is 153.4 ± 0.7 μcal/°K2 g atom and the limiting value of the Debye temperature (θ0c) is 177.0 ± 0.5 °K. For the AuIn alloy γ is 185.9 ± 0.7 μcal/°K2 g atom and θ0c is 159.1 ± 0.3 °K.

Low-temperature Properties of U2Co2InH1.9

2007 ◽  
Vol 62 (7) ◽  
pp. 977-981 ◽  
Author(s):  
Ladislav Havela ◽  
Khrystyna Miliyanchuk ◽  
Laura C. J. Pereira ◽  
Eva Šantavá
Keyword(s):  
High Pressure ◽  
Magnetic Susceptibility ◽  
Specific Heat ◽  
Low Temperatures ◽  
Magnetic Order ◽  
Parent Compound ◽  
Spin Fluctuations ◽  
High Magnetic Fields ◽  
Electronic Specific Heat ◽  
Metamagnetic Transition

Abstract U2Co2InH1.9, synthesized by high-pressure hydrogenation of U2Co2In, crystallizes in the tetragonal structure similar to the parent compound, expanded by 8.4 %. Although U2Co2In is a weak paramagnet, its hydride shows properties suggesting a proximity to the magnetic order. Its magnetic susceptibility exhibits a maximum at T = 2.4 K, ascribed to spin fluctuations. Magnetization at low temperatures goes through a metamagnetic transition between 2 - 3 T. The specific heat characteristics, with a pronounced upturn of Cp/T vs. T at low temperatures which can be fitted using an additional −T 1/2 term, resemble the behaviour of U2Co2Sn. The γ coefficient of the electronic specific heat, reaching 244 mJ mol−1 K−2, is gradually suppressed by high magnetic fields.

Hole density dependence of the low temperature electronic specific heat coefficient of La2-xSrxCaCu2O6 with weakly localized electrons

1993 ◽  
Vol 209 (4) ◽  
pp. 553-558 ◽  
Author(s):  
Takashi Nishikawa ◽  
Shin-ichi Shamoto ◽  
Masafumi Sera ◽  
Masatoshi Sato ◽  
Shigeki Ohsugi ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Density Dependence ◽  
Hole Density ◽  
Electronic Specific Heat ◽  
Specific Heat Coefficient ◽  
Localized Electrons

MAGNETIC AND STRUCTURAL PROPERTIES OF SOME ABa2Cu3O7−δ SUPERCONDUCTORS

1987 ◽  
Vol 01 (03n04) ◽  
pp. 989-992 ◽  
Author(s):  
M.T. Causa ◽  
S.M. Dutrús ◽  
C. Fainstein ◽  
G. Nieva ◽  
H.R. Salva ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Specific Heat ◽  
Powder Diffraction ◽  
Magnetic Moments ◽  
Superconducting Properties ◽  
X Ray ◽  
Structural Modifications

We report here normal and superconducting properties of ABa 2 Cu 3 O 7−δ (with A=Y, Gd, Dy, and Er) and of Fe doped YBa2Cu3O7−δ . Results from X-ray powder diffraction, electrical resistivity, magnetic susceptibility, ESR, and specific heat measurements are presented, leading to a characterization of the magnetic properties of these materials. The effect of structural modifications of the lattice on the superconducting properties and the relative insensitivity of Tc to the presence of magnetic moments is discussed.

Spin Disorder Resistivity and Electronic Specific Heat of Gd4(Co1-xCux)3 Compounds

2008 ◽  
Vol 587-588 ◽  
pp. 333-337
Author(s):  
T.M. Seixas ◽  
M.A. Salgueiro da Silva ◽  
O.F. de Lima ◽  
J. Lopez ◽  
Hans F. Braun ◽  
...  
Keyword(s):  
Specific Heat ◽  
Linear Dependence ◽  
Magnetic Moments ◽  
Spin Fluctuations ◽  
Electronic Specific Heat ◽  
Spin Disorder ◽  
Structure Changes ◽  
Thermal Disorder ◽  
Specific Heat Coefficient ◽  
Electron Band Structure

In this work, we present a study of the spin disorder resistivity ( ρm∞) and the electronic specific heat coefficient ( γ) in Gd4(Co1-xCux)3 compounds, with x = 0, 0.05, 0.10, 0.20, 0.30. The experimental results show a strongly non-linear dependence of ρm∞ on the de Gennes factor which, in similar intermetallic compounds, is usually attributed to the existence of spin fluctuations on the Co 3d bands and its amplification by the thermal disorder of the Gd magnetic moments through the Gd-Co exchange coupling. Using a novel combined analysis of ρm∞ and γ, we show, however, that only electron band structure changes are involved in the anomalous behaviour of ρm∞ and that a linear dependence of ρm∞ on the de Gennes factor is obtained when the variation of the effective mass is properly taken into account.

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