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Full-Text Articles in Physics

Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel Aug 2006

Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Publications

The temperature (4.2–90 K), ac magnetic field (1.25–50 Oe), frequency (5–125 Hz), and bias dc magnetic field (0–10 kOe) dependencies of the real and imaginary components of the ac magnetic susceptibility, and the temperature (4.2–250 K) and dc magnetic field(0.1–50 kOe) dependencies of the dc magnetic susceptibility and magnetization of a(Dy0.5Er0.5)Al2 single crystal have been studied. Isothermal magnetization measurement in a dc magnetic field indicates that (Dy0.5Er0.5)Al2 orders ferromagnetically at 37 K. The ac ...


Spectroscopic Ellipsometry Study Of Optical Anisotropy In Gd5si2ge2 And Comparison With Reflectance Difference Spectra, Joong Mok Park, David W. Lynch, S. J. Lee, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Tsokol, J. E. Snyder, David C. Jiles Jan 2006

Spectroscopic Ellipsometry Study Of Optical Anisotropy In Gd5si2ge2 And Comparison With Reflectance Difference Spectra, Joong Mok Park, David W. Lynch, S. J. Lee, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Tsokol, J. E. Snyder, David C. Jiles

Ames Laboratory Publications

The complex dielectric functions of single crystals of Gd5Si2Ge2 were obtained using spectroscopic ellipsometry (SE) in the photon energy range of 1.5–5.0 eV at room temperature. Reflectance difference (RD) spectra for the a‐b and b‐c planes of single crystals of Gd5Si2Ge2 were derived from these dielectric functions and compared to those obtained from reflectance difference spectroscopy (RDS) at near-normal incidence. The two experimental RD spectra from SE and RDS agreed well. The in-plane optical anisotropy of the sample is mainly due to intrinsic bulk properties ...


Small Sealed Ta Crucible For Thermal Analysis Of Volatile Metallic Samples, Y. Janssen, M. Angst, Kevin W. Dennis, Paul C. Canfield, R. William Mccallum Jan 2006

Small Sealed Ta Crucible For Thermal Analysis Of Volatile Metallic Samples, Y. Janssen, M. Angst, Kevin W. Dennis, Paul C. Canfield, R. William Mccallum

Ames Laboratory Publications

Differential thermal analysis on metallic alloys containing volatile elements can be highly problematic. Here we show how measurements can be performed in commercial, small-sample equipment without modification. This is achieved by using a sealed Ta crucible, easily fabricated from Ta tubing and sealed in a standard arc furnace. The crucible performance is demonstrated by measurements on a mixture of Mg and MgB2, after heating up to 1470°C. We also show data, measured on an alloy with composition Gd40Mg60, that clearly show both the liquidus and a peritectic and are consistent with published phase-diagram data.


Versatile And Compact Capacitive Dilatometer, G. M. Schmiedeshoff, A. W. Lounsbury, D. J. Luna, S. J. Tracy, A. J. Schramm, S. W. Tozer, V. F. Correa, S. T. Hannahs, T. P. Murphy, E. C. Palm, A. H. Lacerda, Sergey L. Bud'ko, Paul C. Canfield, J. L. Smith, J. C. Lashley, J. C. Cooley Jan 2006

Versatile And Compact Capacitive Dilatometer, G. M. Schmiedeshoff, A. W. Lounsbury, D. J. Luna, S. J. Tracy, A. J. Schramm, S. W. Tozer, V. F. Correa, S. T. Hannahs, T. P. Murphy, E. C. Palm, A. H. Lacerda, Sergey L. Bud'ko, Paul C. Canfield, J. L. Smith, J. C. Lashley, J. C. Cooley

Ames Laboratory Publications

We describe the design, construction, calibration, and operation of a relatively simple differential capacitive dilatometer suitable for measurements of thermal expansion and magnetostriction from 300 to below 1K with a low-temperature resolution of about 0.05Å. The design is characterized by an open architecture permitting measurements on small samples with a variety of shapes. Dilatometers of this design have operated successfully with a commercial physical property measurement system, with several types of cryogenic refrigeration systems, in vacuum, in helium exchange gas, and while immersed in liquid helium(magnetostriction only) to temperatures of 30mK and in magnetic fields to 45T.


Three-Dimensional Metallic Photonic Crystals Fabricated By Soft Lithography For Midinfrared Applications, Jae-Hwang Lee, Chang-Hwan Kim, Yong-Sung Kim, Kai-Ming Ho, Kristen P. Constant, Cha-Hwan Oh Jan 2006

Three-Dimensional Metallic Photonic Crystals Fabricated By Soft Lithography For Midinfrared Applications, Jae-Hwang Lee, Chang-Hwan Kim, Yong-Sung Kim, Kai-Ming Ho, Kristen P. Constant, Cha-Hwan Oh

Materials Science and Engineering Publications

We present an efficient method of fabricating freestanding three-dimensional metallic photonic crystals using soft lithography. Low cost and ease of fabrication are achieved through gold sputter deposition on a freestanding woodpile polymer template. We compare experimental results to theoretical calculations for tetragonal and face-centered-tetragonal structures as a function of the number of layers. The photonic crystals behave like full metallic structures with a photonic band edge at a wavelength of 3.5μm. The rejection rates of the structures are about 10dB/layer.


Tribological Properties Of Quasicrystals: Effect Of Aperiodic Versus Periodic Surface Order, Jeong Young Park, D. F. Ogletree, M. Salmeron, R. A. Ribeiro, Paul C. Canfield, Cynthia J. Jenks, Patricia A. Thiel Jan 2006

Tribological Properties Of Quasicrystals: Effect Of Aperiodic Versus Periodic Surface Order, Jeong Young Park, D. F. Ogletree, M. Salmeron, R. A. Ribeiro, Paul C. Canfield, Cynthia J. Jenks, Patricia A. Thiel

Chemistry Publications

We investigated the nanoscale tribological properties of a decagonal quasicrystal using a combination of atomic force microscopy and scanning tunneling microscopy in ultrahigh vacuum. This combination permitted a variety of in situ measurements, including atomic-scale structure, friction and adhesion force, tip-sample current, and topography. We found that thiol-passivated tips can be used for reproducible studies of the tip-quasicrystal contact while nonpassivated probes adhere irreversibly to the clean quasicrystalline surface causing permanent modifications. The most remarkable results were obtained on the twofold surface of the Al-Ni-Co decagonal quasicrystal where atoms are arranged periodically along the tenfold axis and aperiodically in the ...