Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session J7: CM.2 Phase Transitions: Structural Transitions I |
Hide Abstracts |
Chair: C.S. Yoo, Washington State University Room: Grand Crescent |
Tuesday, July 9, 2013 11:00AM - 11:15AM |
J7.00001: Pressure-induced phase transformation of In$_{2}$Se$_{3}$ Anya Rasmussen, Samuel Teklemichael, Elham Mafi, Yi Gu, Matthew McCluskey Phase-change memory, with fast read-write speeds and small dimensions, will soon replace flash memory in our cell phones and tablets. This type of memory relies on phase change materials like indium selenide, In$_{2}$Se$_{3}$, a III-VI semiconductor that exists in multiple crystalline phases. To achieve controlled switching between phases, it is important to understand both the thermal and elastic properties of In$_{2}$Se$_{3}$. Using synchrotron x-ray diffraction and a diamond-anvil cell, a pressure-induced phase transition in powder In$_{2}$Se$_{3}$ from the $\alpha $ phase to $\beta $ phase was discovered at 0.7 GPa. This pressure is an order of magnitude lower than phase-transition pressures in most semiconductors. Raman spectroscopy experiments confirm this result. The bulk moduli are reported for both $\alpha $ and $\beta $ phases, and the $c/a$ ratio for the $\beta $ phase is shown to have a nonlinear dependence on pressure. [Preview Abstract] |
Tuesday, July 9, 2013 11:15AM - 11:30AM |
J7.00002: High pressure study of group-IV clathrate by XRD and Raman scattering Tetsuji Kume, Shigeo Sasaki Group-IV clathrates, which are open-structured Si, Ge, and Sn cage-like compounds, have attracted increasing attention because of their potential applications for thermoelectric devices due to the behavior of phonon-glass and electron-crystal. One of the keys for the intriguing properties is so called rattling vibrations of guests. The direct observation of the rattling is important for understanding of the clathrate properties. Furthermore, the systematic observations of the rattling vibrations as a function of the cage size controlled by pressure are very significant to investigate the guest-host interaction. The pressurization also throws light on the structural stability of the clathrate, which is improved by the guest atoms. The clathrate structure with sp$^{3}$ network is preserved up to very high pressure. Instead of the structural change, the doped Si clathrates undergo an isostructural phase transition. This paper is concerned with the structural stabilities under high pressure and the rattling vibrations of the guest as a function of the cage size, investigated for various semiconductor clathrates (Sr$_{8}$Ga$_{16}$Ge$_{30}$, Eu$_{8}$Ga$_{16}$Ge$_{30}$ and so on) by means of Raman and XRD experiments. On the basis of the recent data, the guest-host interaction is discussed. [Preview Abstract] |
Tuesday, July 9, 2013 11:30AM - 11:45AM |
J7.00003: Pressure effect on the isostructural transition in RNiAl compounds (R$=$Tb and Gd) Jiri Prchal, Milan Klicpera, Petr Dolezal, Jiri Kastil, Martin Misek, Pavel Javorsky TbNiAl and GdNiAl belong to a large group of compounds crystallizing in the hexagonal ZrNiAl-type of structure. Within recent years, physics of the discontinuity in the temperature or composition dependence of the lattice parameters (a and c) observed in several compounds of this family of intermetallics has been of particular interest. These materials have in common a specific ``forbidden'' value of the c/a ratio. This conclusion has been corroborated by ab initio calculations [1]. Although the dramatic structure change is hardly observable in the temperature dependence of the specific heat, it is accompanied with a clear change of the effective magnetic moment, change of the crystal field energy spectra [2] and namely with increasing amount of mechanical defects in the sample. TbNiAl as a representative of such behavior, exhibits a first-order structural transition at low temperatures around 100K [3]. We have for the first time studied this structural step upon application of hydrostatic pressure on both -- poly- and monocrystal of TbNiAl and a polycrystalline GdNiAl, in which the structural step appears still higher - around 240K. Our experimental observation of an unusually rapid decrease of the critical temperature with pressure will be discussed in terms of differences in the strength of the inter- and intraplanar chemical bonding in this type of structure. [1] J. Prchal et al., Phys. Rev. B 77 (2008) 134106. [2] P. Javorsky et al., J Magn. Magn. Mat. 317 (2007) e400. [3] J. Prchal et al., Physica B 378-380 (2006) 1102. [Preview Abstract] |
Tuesday, July 9, 2013 11:45AM - 12:00PM |
J7.00004: Pressure Induced Phase Transitions of Yb: NaBi(WO$_{4})_{2}$ up to 51 GPa Hang Cui, Chunli Ma, Xiaoxin Wu, Hongyang Zhu, Hongdong Li, Qliang Cui High-pressure Raman scattering and luminescence spectra studies have been performed on Yb: NaBi(WO$_{4})_{2}$ up to 51 GPa at room temperature by using diamond anvil cell techniques. The Yb-doped single crystals of scheelite double tungstates NaBi(WO$_{4})_{2}$ have been grown by Czochralski method. High-pressure Raman scattering results indicate that Yb: NaBi(WO$_{4})_{2}$ undergoes phase transition from tetragonal (I4$_{1}$/a) to monoclinic (I2/a) symmetry at around 6.5 GPa. When the pressure reaches to 23.3 GPa, the color of sample changes from yellow to red observed by optical microscope, and the luminescence spectra is dramatically different from the previous phase, it is indicated that the energy level transition maybe occurs around this pressure. With pressure is higher than 32.1 GPa, Raman and luminescence spectra suddenly disappear and the Yb:NaBi(WO$_{4})_{2}$ ultimately transforms into amorphous state. The mechanism of various phase transitions caused by the effect of Yb-doping is still in the going work. [Preview Abstract] |
Tuesday, July 9, 2013 12:00PM - 12:15PM |
J7.00005: On the phase diagrams of the helimagnets MnSi and Cu$_2$OSeO$_3$ Sergei M. Stishov, Alla E. Petrova, V.A. Sidorov A series of resistivity measurements on a MnSi single crystal was performed at high pressures, created by a piston-cylinder device with a liquid pressure medium. The form of the resistivity curve at ambient pressure clearly indicates a first order nature of the magnetic phase transition in MnSi. Application of high pressure rapidly degrades the first order features of the phase transition. The temperature derivative of resistivity demonstrates two notable features of the phase transition that disappear on increasing pressure: a sharp peak marking the first order phase transition and a shallow maximum situated slightly above the critical temperature and pointing to prominent helical fluctuations. The current experimental data rule out any strong first order phase transition in MnSi at high pressures and low temperatures, which would prevent development of a quantum critical region. On the contrary, there should exist true quantum critical phenomena in MnSi at high pressures because a weak first order transition, if it survives at high pressures to the lowest temperatures, should not suppress the entire quantum critical region. Recently a dielectric compound Cu$_2$OSeO$_3$ possessing a cubic non-centro symmetric P2$_1$3 crystal structure, like MnSi was found to have a magnetic structure and T-H magnetic diagram similar to those of MnSi [1]. We have studied the magnetic transition in this material by means of magnetic ac-susceptibility and ac-calorimetry at nearly hydrostatic pressure up to 6 GPa. The data obtained are analyzed in hope to understand the nature of the chiral fluctuation region adjacent to the helical phase transitions. [Preview Abstract] |
Tuesday, July 9, 2013 12:15PM - 12:30PM |
J7.00006: Second harmonic generation measurements for the determination of pressure induced phase transitions Lkhamsuren Bayarjargal, Bjoern Winkler We show that optical second harmonic generation measurements can be used to efficiently delineate phase boundaries in high pressure experiments in diamond anvil cells and understand transition pathways. We have employed SHG measurements to study the pressure-induced structural phase transitions in AlN and ZnO as a function of temperature and of particle size. Furthermore, we demonstrate that pressure-induced magnetic phase transitions can be detected by this approach and show that the transition from an acentric to a centrosymmetric magnetic structure occurs in Cr$_2$O$_3$ at 10(1) GPa. The pressure dependence of the Neel temperature, d$T_N$/d$p$ = -1.0(2) K/GPa from our SHG measurements, which differs significantly from earlier results where d$T_N$/d$p$ ranged from -16 K/GPa to +15 K/GPa. Further examples, where SHG measurements have provided information on pressure induced structural phase transitions are the cases of KIO$_3$, where two transitions at 7 and 14 GPa were identified, and of ice VII, where SHG measurements do not support a proposed acentric high pressure modification. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700