Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session B5: Material Growth and Characterization I |
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Chair: Micky Holcomb, West Virginia University Room: Waterfront Hotel Wharf AB |
Saturday, October 24, 2015 3:30PM - 3:42PM |
B5.00001: La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ interfaces examined by synchrotron x-rays Jinling Zhou, Vu Thanh Tra, Shuai Dong, Robbyn Trappen, Matthew A. Marcus, Catherine Jenkins, Charles Frye, Evan Wolfe, Ryan White, Srinivas Polisetty, Jiunn-Yuan Lin, James LeBeau, Ying-Hao Chu, Mikel Barry Holcomb Magnetoelectric coupling is a coupling effect between the magnetic and electric orders of matter. Magnetoelectric interfaces between La0.7Sr0.3MnO3 (LSMO)/PbZr0.2Ti0.8O3 (PZT) thin films have been investigated by valence sensitive x-ray absorption spectroscopy. Mn valence depth profile was obtained by taking advantage of the depth sensitivity of the measurement methods. The interfacial Mn valence was found to be smaller than in the bulk, where PZT polarization played a role. Mn valence gradually increased to a relatively constant value as PZT transits from monodomain to polydomain along the PZT thickness gradient. Mn valence consistently became larger/smaller when PZT was poled away from/towards LSMO. These research results are consistent with the charge modulated interfacial magnetoelectric coupling mechanism and may shine light on creating magnetoelectric coupled interfaces. [Preview Abstract] |
Saturday, October 24, 2015 3:42PM - 3:54PM |
B5.00002: Excitations of an Ising Ferromagnet in a Transverse Magnetic Field at Quantum Criticality Ivelisse M. Cabrera, Jordan D. Thompson, Radu Coldea, Dharmalingam Prabhakaran, Robert I. Bewley, Tatiana Guidi The Ising chain in a transverse magnetic field is one of the best-known theoretical models for a continuous quantum phase transition. In this model, a magnetic field transverse to the Ising spin axis drives the system from a spontaneously ordered phase to a quantum paramagnetic phase, where very distinct magnetic excitations are expected on each side of the quantum phase transition. The mechanism driving this phase transition has long been predicted to involve the closing of the spin gap, or minimum excitation energy, at the quantum critical point, where a characteristic linear dispersion is expected at low energies. We report single-crystal neutron scattering measurements that unveil how the magnetic order and excitations evolve in the very close proximity of the quantum critical point in the quasi-1D Ising chain ferromagnet CoNb$_2$O$_6$. Near criticality, we observe an essentially gapless spectrum with an almost perfectly-linear dispersion along the chain direction. To our knowledge, this is the first time that essentially-gapless, linearly dispersive excitations have been observed in the very close proximity of a transverse field-tuned quantum critical point. [Preview Abstract] |
Saturday, October 24, 2015 3:54PM - 4:06PM |
B5.00003: Depth dependent atomic valence determination by synchrotron techniques Robbyn Trappen, Mikel Holcomb, Jinling Zhou, Ying-Hao Chu, Vu Tra We investigate the layer-dependent atomic valence in magnetoelectric La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures. X-ray absorption spectroscopy measurements were taken in both bulk-sensitive fluorescence yield and surface-sensitive total electron yield mode to determine the Mn valence. These measurements were taken at the Advanced Light Source at Lawrence Berkeley National Labs. The experimentally measured valence is modeled and compared with theory to determine the layer-by-layer atomic valence. [Preview Abstract] |
Saturday, October 24, 2015 4:06PM - 4:18PM |
B5.00004: \textbf{Geometric Magnetic Frustration in Li}$_{\mathrm{\mathbf{3}}}$\textbf{Mg}$_{\mathrm{\mathbf{2}}}$\textbf{OsO}$_{\mathrm{\mathbf{6}}}$\textbf{ Studied with Muon Spin Relaxation} J. P. Carlo, S. Derakshan, J. E. Greedan Geometric frustration manifests when the spatial arrangement of ions inhibits magnetic order. Typically associated with antiferromagnetically (AF)-correlated moments on triangular or tetrahedral lattices, frustration occurs in a variety of structures and systems, resulting in rich phase diagrams and exotic ground states. As a window to exotic physics revealed by the cancellation of normally dominant interactions, the research community has taken great interest in frustrated systems. One family of recent interest are the rock-salt ordered oxides A$_{\mathrm{5}}$BO$_{\mathrm{6}}$, in which the B sites are occupied by magnetic ions comprising a network of interlocked tetrahedra, and nonmagnetic ions on the A sites control the B oxidation state through charge neutrality. Here we will discuss studies of Li$_{\mathrm{3}}$Mg$_{\mathrm{2}}$OsO$_{\mathrm{6}}$ using muon spin relaxation ($\mu $SR), a highly sensitive local probe of magnetism. Previous studies of this family included Li$_{\mathrm{5}}$OsO$_{\mathrm{6}}$, which exhibits AF order below 50K with minimal evidence for frustration, and Li$_{\mathrm{4}}$MgReO$_{\mathrm{6}}$, which exhibits glassy magnetism. Li$_{\mathrm{3}}$Mg$_{\mathrm{2}}$RuO$_{\mathrm{6}}$, meanwhile, exhibits long-range AF, with the ordering temperature suppressed by frustration. But its isoelectronic twin, Li$_{\mathrm{3}}$Mg$_{\mathrm{2}}$OsO$_{\mathrm{6}}$ (5$d^{\mathrm{3}}$ vs. 4$d^{\mathrm{3}})$ exhibits very different behavior, revealed by $\mu $SR to be a glassy ground state below 12K. Understanding why such similar systems exhibit diverse ground-state behavior is key to understanding the nature of geometric magnetic frustration. [Preview Abstract] |
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