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Full-Text Articles in Physics

Phase Relationships And Structural, Magnetic, And Thermodynamic Properties Of Alloys In The Pseudobinary Er5si4-Er5ge4 System, A. O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso Oct 2004

Phase Relationships And Structural, Magnetic, And Thermodynamic Properties Of Alloys In The Pseudobinary Er5si4-Er5ge4 System, A. O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The room temperature crystal structures of Er5SixGe4−x alloys change systematically with the concentration of Ge from the orthorhombic Gd5Si4-type when x=4, to the monoclinic Gd5Si2Ge2 type when 3.5⩽x⩽3.9 and to the orthorhombic Sm5Ge4 type forx⩽3. The Curie-Weiss behavior of Er5SixGe4−x materials is consistent with the Er3+ state. The compounds order magnetically below 30 K, apparently adopting complex noncollinear magnetic structures with magnetization not reaching saturation in 50 kOe magnetic fields ...


Bridgman-Grown I-Al68.9pd21.6mn9.5 Quasicrystal: Comparison Of Α, Cp, Σ, And Χ With Those For Flux-Grown Samples, Clayton A. Swenson, Thomas A. Lograsso, N. E. Anderson Jr., A. R. Ross Sep 2004

Bridgman-Grown I-Al68.9pd21.6mn9.5 Quasicrystal: Comparison Of Α, Cp, Σ, And Χ With Those For Flux-Grown Samples, Clayton A. Swenson, Thomas A. Lograsso, N. E. Anderson Jr., A. R. Ross

Ames Laboratory Publications

Thermal expansivity (α, 1–300 K), heat capacity (CP, 1–108 K), electrical conductivity (σ, 1–300 K) and magnetic susceptibility (χ, 1–300 K) data have been obtained for a Bridgman-grown single grain i-Al68.9Pd21.6Mn9.5 quasicrystal (BR) for direct comparison with data previously published for a flux-grown single grain sample [ Phys. Rev. B 65 184206 (2002)], and present σ, χ and CP data for a second flux-grown sample described in an earlier publication [ Philos. Mag. B 79 1673 (1999)]. Fortuitously, comparative analyses show these samples to have essentially the same ...


Elastic Constants Of Ni-Mn-Ga Magnetic Shape Memory Alloys, Marcelo Stipcich, Lluís Mañosa, Antoni Planes, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso, C. Stassis Aug 2004

Elastic Constants Of Ni-Mn-Ga Magnetic Shape Memory Alloys, Marcelo Stipcich, Lluís Mañosa, Antoni Planes, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso, C. Stassis

Ames Laboratory Publications

We have measured the adiabatic second order elastic constants of two Ni-Mn-Ga magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant C′ has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structural ...


Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder Aug 2004

Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder

Materials Science and Engineering Publications

The electrical transport properties of semiconducting AlMgB14films deposited at room temperature and 573K are reported in this letter. The as-deposited films are amorphous, and they exhibit high n-type electrical conductivity, which is believed to stem from the conduction electrons donated by Al, Mg, and/or Fe impurities in these films. The film deposited at 573K is less conductive than the room-temperature-deposited film. This is attributed to the nature of donor or trap states in the band gap related to the different deposition temperatures.


Magnetostriction And Elasticity Of Body Centered Cubic Fe100−Xbex Alloys, A. E. Clark, M. Wun-Fogle, J. B. Restorff, Thomas A. Lograsso, G. Petculescu Jun 2004

Magnetostriction And Elasticity Of Body Centered Cubic Fe100−Xbex Alloys, A. E. Clark, M. Wun-Fogle, J. B. Restorff, Thomas A. Lograsso, G. Petculescu

Ames Laboratory Conference Papers, Posters, and Presentations

Magnetostriction measurements from 77 K to room temperature on oriented (100) and (110) disk samples of Fe93.9Be6.1 and Fe88.7Be11.3 reveal substantial increases in λ100compared to iron. For the 11.3% alloy, λ100=110 ppm, a sixfold increase above that of α-Fe. For the 6.1% alloy, λ100=81 ppm, ∼40% and ∼170% greater than λ100 of comparable Fe–Ga and Fe–Al alloys, respectively, for H=15 kOe. Large differences exist between the values of λ100 and λ111 (λ100>0, λ111 ...


Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles Jun 2004

Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The system Gd5(SixGe1−x)4 for 0.4⩽x⩽0.5 has been shown to have an unusual first order, coupled magnetic-structural phase transformation at the Curie temperature. Above the transformation temperature Tc, the material is paramagnetic with a monoclinic structure; below Tc, it is ferromagnetic with an orthorhombic structure. Another unusual feature of this phase transformation is that an applied magnetic field can increase Tc by 5 K per tesla. In this study, the magnetic-structural transformation in single crystalGd5Si2Ge2 was triggered by holding the sample at ...


Giant Magnetostriction Behavior At The Curie Temperature Of Single Crystal Gd5(Si0.5ge0.5)4, M. Han, David C. Jiles, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel Jun 2004

Giant Magnetostriction Behavior At The Curie Temperature Of Single Crystal Gd5(Si0.5ge0.5)4, M. Han, David C. Jiles, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Conference Papers, Posters, and Presentations

We report results of thermal expansion (TE) and magnetostriction (MS) measurements on a single crystal sample of Gd5(Si0.5Ge0.5)4 prepared by the Bridgman method. TE and MS were measured along the c axis by the strain gauge method and the temperature was controlled using a closed cycle helium refrigerator. From the TE measurements the magnetic structural phase transition temperature was found to be 259.5 K on cooling and 261.5 K on heating. The abrupt change in strain and the temperature hysteresis indicate that it is a first order transition. MS measurements ...


Reversible Spin-Flop And Irreversible Metamagneticlike Transitions Induced By A Magnetic Field In The Layered Gd5ge4 Antiferromagnet, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel, Vitalij K. Pecharsky Apr 2004

Reversible Spin-Flop And Irreversible Metamagneticlike Transitions Induced By A Magnetic Field In The Layered Gd5ge4 Antiferromagnet, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel, Vitalij K. Pecharsky

Ames Laboratory Publications

Temperature and magnetic field dependencies of the magnetization of single crystal Gd5Ge4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ∼8.4kOe is applied along the cdirection, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd3+ ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd5Ge4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of ...


Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch Mar 2004

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Ames Laboratory Publications

Reflectance difference (RD) spectra for the ab plane of the single crystals of Gd5Si2Ge2and bc planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the bc planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the ...