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Full-Text Articles in Physics

Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield Dec 2012

Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield

Ames Laboratory Publications

We present heat capacity, c-axis thermal expansion and pressure-dependent, low-field, temperature-dependent magnetization for pressures up to ∼12 kbar, data for KFe2As2 single crystals. Tc decreases under pressure with dTc/dP≈−0.10 K/kbar. The inferred uniaxial, c-axis, pressure derivative is positive, dTc/dpc≈0.11 K/kbar. The data are analyzed in comparison with those for overdoped Fe-based superconductors. Arguments are presented that superconductivity in KFe2As2 may be different from the other overdoped, Fe-based materials in the 122 family.


Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-Gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu Oct 2012

Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-Gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu

Ames Laboratory Publications

Topological insulators, a new quantum state of matter, create exciting opportunities for studying topological quantum physics and for exploring spintronic applications due to their gapless helical metallic surface states. Here, we report the observation of weak anti-localization and quantum oscillations originated from surface states in Bi2Se2Te crystals. Angle-resolved photoemission spectroscopy measurements on cleaved Bi2Se2Te crystals show a well-defined linear dispersion without intersection of the conduction band. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model and the extracted phase coherent length shows a power-law dependence with temperature ( ∼T−0.44), indicating the presence of the surface states. More ...


X-Ray Diffuse Scattering Measurements Of Chemical Short-Range Order And Lattice Strains In A Highly Magnetostrictive Fe0.813ga0.187 Alloy In An Applied Magnetic Field, Yingzhou Du, Mianliang Huang, Thomas A. Lograsso, Robert J. Mcqueeney Jun 2012

X-Ray Diffuse Scattering Measurements Of Chemical Short-Range Order And Lattice Strains In A Highly Magnetostrictive Fe0.813ga0.187 Alloy In An Applied Magnetic Field, Yingzhou Du, Mianliang Huang, Thomas A. Lograsso, Robert J. Mcqueeney

Ames Laboratory Publications

The rapid growth of the magnetostriction coefficient of ferromagnetic Fe1−xGax alloys that occurs at a composition range from 0


Structural Properties And Relative Stability Of (Meta)Stable Ordered, Partially Ordered, And Disordered Al-Li Alloy Phases, Aftab Alam, Duane D. Johnson Apr 2012

Structural Properties And Relative Stability Of (Meta)Stable Ordered, Partially Ordered, And Disordered Al-Li Alloy Phases, Aftab Alam, Duane D. Johnson

Ames Laboratory Publications

We resolve issues that have plagued reliable prediction of relative phase stability for solid solutions and compounds. Due to its commercially important phase diagram, we showcase the Al-Li system because historically density-functional theory (DFT) results show large scatter and limited success in predicting the structural properties and stability of solid solutions relative to ordered compounds. Using recent advances in an optimal basis-set representation of the topology of electronic charge density (and, hence, atomic size), we present DFT results that agree reasonably well with all known experimental data for the structural properties and formation energies of ordered, off-stoichiometric partially ordered, and ...


Temperature Dependence Of Magnetoelastic Properties Of Fe100−Xsix (5 < X < 20), G. Petculescu, P. K. Lambert, A. E. Clark, K. B. Hathaway, Qingfeng Xing, Thomas A. Lograsso, J. B. Restorff, M. Wun-Fogle Feb 2012

Temperature Dependence Of Magnetoelastic Properties Of Fe100−Xsix (5 < X < 20), G. Petculescu, P. K. Lambert, A. E. Clark, K. B. Hathaway, Qingfeng Xing, Thomas A. Lograsso, J. B. Restorff, M. Wun-Fogle

Ames Laboratory Conference Papers, Posters, and Presentations

Tetragonal magnetostriction (λγ,2) and elastic constants (c′, c44, and c11) for Fe100−xSixwere measured as a function of temperature (T). Compositions corresponding to the disordered A2 (x = 5), ordered D03 (x = 19.8), and mixed (x = 11.6) phases, were investigated. The magnetoelastic coupling (−b1) was determined for 77 < T < 300 K and compared with those of Fe-Ga, Fe-Ge, and Fe-Al. Both λγ,2(T) and −b1(T) of Fe-Si behave similarly to those of Fe-Ge, while other notable differences exist between the measured properties of Fe-Si and those of the other three alloys. Due to the early establishment of short ...


Coexistence Of Charge-Density Wave And Ferromagnetism In Ni2mnga, S. W. D'Souza, Abhishek Rai, J. Nayak, M. Maniraj, R. S. Dhaka, S. R. Barman, Deborah L. Schlagel, Thomas A. Lograsso, Aparna Chakrabarti Feb 2012

Coexistence Of Charge-Density Wave And Ferromagnetism In Ni2mnga, S. W. D'Souza, Abhishek Rai, J. Nayak, M. Maniraj, R. S. Dhaka, S. R. Barman, Deborah L. Schlagel, Thomas A. Lograsso, Aparna Chakrabarti

Ames Laboratory Publications

We demonstrate the existence of a charge-density-wave (CDW) associated with an incommensurate periodic lattice distortion on Ni2MnGa surface in the ferromagnetic state. Our temperature-dependent photoemission spectra provide compelling evidence of a pseudogap at the Fermi level for TCDW ⩽ 270 K that appears at the onset of the premartensite phase and persists in the martensite phase. While the width of the pseudogap is about 25 meV, a spectral weight transfer is observed over a much wider energy range that is associated with the CDW.


Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu Jan 2012

Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu

Ames Laboratory Publications

This paper presents a comparative study on the tetragonal magnetostriction constant,λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ∼10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus ...