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Full-Text Articles in Physics

Linear Thermal Expansivity (1–300 K), Specific Heat (1–108 K), And Electrical Resistivity Of The Icosahedral Quasicrystal I-Al61.4cu25.4fe13.2, Clayton A. Swenson, Thomas A. Lograsso, A. R. Ross, N. E. Anderson Jr. Nov 2002

Linear Thermal Expansivity (1–300 K), Specific Heat (1–108 K), And Electrical Resistivity Of The Icosahedral Quasicrystal I-Al61.4cu25.4fe13.2, Clayton A. Swenson, Thomas A. Lograsso, A. R. Ross, N. E. Anderson Jr.

Ames Laboratory Publications

Linear thermal expansivity (α, 1–300 K), heat capacity (Cp, 1–108 K), and electrical resistivity (ρ, 1–300 K) measurements are reported for single grain i-Al61.4Cu25.4Fe13.2 quasicrystals as a function of sample processing. While ρ(T) is sensitive to sample treatment, both Cp and α are relatively insensitive (to a few percent) except at the lowest temperatures (below 4 K), where an inverse correlation between ρ and the electronic Cp coefficient γ appears to exist. Dispersion effects (deviations from Debye-like behavior) in both Cp and the lattice ...


Bulk Termination Of The Quasicrystalline Fivefold Surface Of Al70pd21mn9, Z. Papadopolos, G. Kasner, J. Ledieu, E. J. Cox, N. V. Richardson, Q. Chen, R. D. Diehl, Thomas A. Lograsso, A. R. Ross, R. Mcgrath Nov 2002

Bulk Termination Of The Quasicrystalline Fivefold Surface Of Al70pd21mn9, Z. Papadopolos, G. Kasner, J. Ledieu, E. J. Cox, N. V. Richardson, Q. Chen, R. D. Diehl, Thomas A. Lograsso, A. R. Ross, R. Mcgrath

Ames Laboratory Publications

The structure of the Al70Pd21Mn9 surface has been investigated using high-resolution scanning tunneling microscopy. From two large fivefold terraces on the surface in a short decorated Fibonacci sequence, atomically resolved surface images have been obtained. One of these terraces carries a rare local configuration in the form of a ring. The location of the corresponding sequence of terminations in the bulk model M of icosahedral i-AlPdMn based on the three-dimensional tiling T*(2F) of an F phase has been estimated using this ring configuration and the requirement from low-energy electron diffraction work of Gierer et ...


Structural Studies Of Fe0.81ga0.19 By Reciprocal Space Mapping, D. Viehland, Jiefang Li, Thomas A. Lograsso, A. R. Ross, Manfred Wuttig Oct 2002

Structural Studies Of Fe0.81ga0.19 By Reciprocal Space Mapping, D. Viehland, Jiefang Li, Thomas A. Lograsso, A. R. Ross, Manfred Wuttig

Ames Laboratory Publications

Reciprocal lattice mapping has been performed on Fe0.81Ga0.19 crystals by ω–ω/2θ, Ψ–ϕ, and ω–ϕ scans. A strong elongation of the 〈001〉c peak was found along the〈110〉c direction. ω scans revealed short lateral correlation lengths ξ along 〈110〉cand strong diffuse scattering along the 〈001〉c. Multiple domains with monoclinic symmetry (angle ∼190°) were observed by Ψ–ϕ and ω–ϕ scans on the (001)c face, and were also tilted with respect to each other. The results show an average cubic structure with orthorhombic structural modulations, and ...


Morphological Evolution Of The Fivefold Surface Of I-Alpdmn Quasicrystals, Giovanni Cappello, Joël Chevrier, Frank Schmithüsen, Andreas Stierle, Vincenzo Formoso, Fabio Comin, Marc De Boissieu, Michel Boudard, Thomas A. Lograsso, Cynthia J. Jenks, Dwight Delaney May 2002

Morphological Evolution Of The Fivefold Surface Of I-Alpdmn Quasicrystals, Giovanni Cappello, Joël Chevrier, Frank Schmithüsen, Andreas Stierle, Vincenzo Formoso, Fabio Comin, Marc De Boissieu, Michel Boudard, Thomas A. Lograsso, Cynthia J. Jenks, Dwight Delaney

Ames Laboratory Publications

Morphology of the fivefold symmetric quasicrystal surface of AlPdMn was investigated by x-ray reflectivity and by x-ray diffraction. X-ray experiments revealed two different morphologies depending on the surface preparation. Sputtering and annealing up to 900 K, under UHV conditions, produced a rough and facetted quasicrystal surface. These features were confirmed by atomic force microscopy and scanning tunnel microscopy measurements. We also observed that an annealing above 900 K induces a rapid and irreversible transition toward a flat surface.


Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles May 2002

Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles

Center for Nondestructive Evaluation Publications

A relationship between the parameters of a hysteretic-stochastic process model of the Barkhausen effect (BE) and the microstructural features of a series of ferritic/pearlitic steel samples has been identified. The root-mean-square values and pulse height distributions of the experimental and modeled BE signals showed similar dependence on the pearlite content. The correlation length parameter ξ of the model, which represents the range of interaction of domain walls with pinning sites, was found to obey ξ=AVfDf+BVpDp where Vf(Vp)and Df(Dp) are the volume fraction and grain size of ferrite (pearlite).


Quadrupolar And Dipolar Contributions To X-Ray Magnetic Circular Dichroism At The Tb L3,2 Edges: Experiment Versus Theory, H. Wende, Z. Li, A. Scherz, G. Ceballos, K. Baberschke, A. Ankudinov, J. J. Rehr, F. Wilhelm, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso May 2002

Quadrupolar And Dipolar Contributions To X-Ray Magnetic Circular Dichroism At The Tb L3,2 Edges: Experiment Versus Theory, H. Wende, Z. Li, A. Scherz, G. Ceballos, K. Baberschke, A. Ankudinov, J. J. Rehr, F. Wilhelm, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

We investigate the x-ray magnetic circular dichroism (XMCD) at the L3,2 edges using a single crystal of Tb as a prototype system for a one-element magnet in order to ascertain the multipolar nature of the features in the dichroic spectra. The high resolution of the experimental data allows for a clear identification of the dipolar (E1: 2p→5d) and quadrupolar (E2: 2p→4f) transitions. On the basis of ab initio calculations we developed a simple procedure to extract the quadrupolar part by subtracting the derivative of the spin-averaged absorption spectra from the ...


Temperature And Stress Dependencies Of The Magnetic And Magnetostrictive Properties Of Fe0.81ga0.19, R. A. Kellogg, Alison B. Flatau, A. E. Clark, M. Wun-Fogle, Thomas A. Lograsso May 2002

Temperature And Stress Dependencies Of The Magnetic And Magnetostrictive Properties Of Fe0.81ga0.19, R. A. Kellogg, Alison B. Flatau, A. E. Clark, M. Wun-Fogle, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

It was recently reported that the addition of nonmagnetic Ga increased the saturation magnetostriction (λ100) of Fe over tenfold while leaving the rhombohedral magnetostriction (λ111) almost unchanged. To determine the relationship between the magnetostriction and the magnetization we measured the temperature and stress dependence of both the magnetostriction and magnetization from −21 °C to +80 °C under compressive stresses ranging from 14.4 MPa to 87.1 MPa. For this study a single crystal rod of Fe0.81Ga0.19 was quenched from 800 °C into water to insure a nearly random distribution of Ga atoms ...


Magnetostriction Of Ternary Fe–Ga–X Alloys (X=Ni,Mo,Sn,Al), J. B. Restorff, M. Wun-Fogle, A. E. Clark, Thomas A. Lograsso, A. R. Ross, Deborah L. Schlagel May 2002

Magnetostriction Of Ternary Fe–Ga–X Alloys (X=Ni,Mo,Sn,Al), J. B. Restorff, M. Wun-Fogle, A. E. Clark, Thomas A. Lograsso, A. R. Ross, Deborah L. Schlagel

Ames Laboratory Publications

Investigations were made into the effect of small additions of Ni, Mo, Sn, as well as larger additions of Al on the magnetostriction of single crystal Fe100−xGax alloys (x≅13). The Fe–Ga and Fe–Al systems are seemingly unique among the Fe-based alloys in having very large magnetostrictions in spite of Ga and Al being nonmagnetic. In this paper, we show how additions of Ni, Mo, Sn, and Al affect λ100 and λ111 of the binary Fe–Ga alloys. We substituted small amounts of Ni into a binary Fe–Ga alloy in an ...


Magnetothermal Properties Of Single Crystal Dysprosium, A. S. Chernyshov, A. M. Tishin, Karl A. Gschneidner Jr., A. O. Pecharsky, Vitalij K. Pecharsky, Thomas A. Lograsso Jan 2002

Magnetothermal Properties Of Single Crystal Dysprosium, A. S. Chernyshov, A. M. Tishin, Karl A. Gschneidner Jr., A. O. Pecharsky, Vitalij K. Pecharsky, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

The magnetocaloric properties (the adiabatic temperature change) of the high purity single crystalline dysprosium have been measured directly over the temperature range from 78 to 220 K in magnetic fields from 0 to 14 kOe applied along the easy magnetization direction (a-axis). These results are in good to excellent agreement, except for two regions (105 to 127 K, and 179 to 182 K), with the previous magnetocaloric effect data reported on lower purity dysprosium samples. The magnetic phase diagram of Dy has been refined based on the results of these measurements and two new high magnetic field phases have ...