9,331 research outputs found
Letter from Thos. J. Henley to Chas. E. Mix with affidavits of T. M. Ames and H. L. Ford, 1858
No full textHis reply to charges against him by J. Ross Browne. Includes an extraction from his letter of April 19, 1858, and affidavits from T. M. Ames and H. L. Ford
Substantial reduction of the anisotropy in the critical current densities J cof Ni-doped CaKFe4As4single crystals by chemical and irradiation-induced disorder
No full textWe demonstrate that the anisotropy in the critical current densities, J c, of CaK(Fe1-x Ni x )4As4 (x = 0, 0.015, 0.025, and 0.030) single crystals reduces with increasing chemical and irradiation-induced disorder. The magnetic field dependences of J c are analyzed by performing magnetization measurements with H applied parallel and perpendicular to the crystallographic c-axis. The results show that undoped crystals display large anisotropies in J c due to an enhancement of the vortex pinning with H applied parallel to the crystallographic ab-planes. This anisotropy reduces substantially as Ni addition increases. Moreover, we found that random disorder introduced by proton irradiation enhances mainly the vortex pinning for H parallel to the c-axis. Consequently, using adequate fluencies, the vortex pinning at low temperatures in both undoped and doped samples becomes close to isotropic. These results make the CaKFe4As4 system promising for applications that require isotropic J c under magnetic fields.Fil: Haberkorn, Nestor Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: Xu, M.. University Of Iowa. Ames Laboratory; Estados UnidosFil: Meier, W.R.. University Of Iowa. Ames Laboratory; Estados UnidosFil: Schmidt, J.. University Of Iowa. Ames Laboratory; Estados UnidosFil: Suarez, Sergio Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: Bud'ko, S.L.. University Of Iowa. Ames Laboratory; Estados UnidosFil: Canfield, P. C.. University Of Iowa. Ames Laboratory; Estados Unido
Orbital character of the spin-reorientation transition in TbMn6Sn6
No full textFerromagnetic (FM) order in a two-dimensional kagome layer is predicted to generate a topological Chern insulator without an applied magnetic field. The Chern gap is largest when spin moments point perpendicular to the kagome layer, enabling the capability to switch topological transport properties, such as the quantum anomalous Hall effect, by controlling the spin orientation. In TbMn6Sn6, the uniaxial magnetic anisotropy of the Tb3+ ion is effective at generating the Chern state within the FM Mn kagome layers while a spin-reorientation (SR) transition to easy-plane order above TSR=310 K provides a mechanism for switching. Here, we use inelastic neutron scattering to provide key insights into the fundamental nature of the SR transition. The observation of two Tb excitations, which are split by the magnetic anisotropy energy, indicates an effective two-state orbital character for the Tb ion, with a uniaxial ground state and an isotropic excited state. The simultaneous observation of both modes below TSR confirms that orbital fluctuations are slow on magnetic and electronic time scales < ps and act as a spatially-random orbital alloy. A thermally-driven critical concentration of isotropic Tb ions triggers the SR transition.This article is published as Riberolles, S. X. M., Tyler J. Slade, R. L. Dally, P. M. Sarte, Bing Li, Tianxiong Han, H. Lane et al. "Orbital character of the spin-reorientation transition in TbMn6Sn6." Nature Communications 14, no. 1 (2023): 1-8.
DOI: 10.1038/s41467-023-38174-5.
Copyright 2023 The Author(s).
Posted with permission.
DOE Contract Number(s): AC02-07CH11358
Targeted Dy intercalation under graphene/SiC for tuning its electronic band structure
No full textMetal intercalation of graphene is a promising method to tune its electronic band structure and generate novel
electronic and topological phases. The tuning depends critically on the ability to bond the intercalated atoms at
predesigned, subsurface interlayer locations because the emerging band structure depends on metal location.We
have studied Dy intercalation under single-layer graphene (SLG) on SiC using spot profile analysis–low-energy
electron diffraction and scanning tunneling microscopy (STM). The experimental work is complemented with
density-functional theory (DFT) analysis. Because different diffraction spots originate from different subsurface
interlayer regions, it is possible to identify changes in the intercalation location by monitoring the spot intensity
as a function of growth conditions. DFT calculations of the chemical potential as a function of intercalated Dy
coverage support the variation of the stability of the intercalated phase at different intercalated locations. The
preferred location is confirmed from STM studies showing the removal of the 6 × 6 moiré corrugation at the
preferred location, observed at higher Dy coverage.This article is published as Chen, S., Y. Han, M. Kolmer, J. Hall, M. Hupalo, J. W. Evans, and M. C. Tringides. "Targeted Dy intercalation under graphene/SiC for tuning its electronic band structure." Physical Review B 107, no. 4 (2023): 045408.
DOI: 10.1103/PhysRevB.107.045408.
Copyright 2023 American Physical Society.
Posted with permission.
DOE Contract Number(s): AC02-07CH1135
Author Ben Ames Williams first met Searsmont farmer Bert McCorrison in 1918, a m
No full textAuthor Ben Ames Williams first met Searsmont farmer Bert McCorrison in 1918, a meeting which the author said had a profound impact on his professional career. McCorrison died in 1931, leaving Williams his Hardscrabble Farm in Searsmount, which became the author\u27s home until his death in 1953
Letter from Thos. J. Henley to Chas. E. Mix with other correspondences and statement, 1858
No full textEnclosed copies of letters and statements from Sub Agent H. L. Ford, Dr. Ames, and A. W. Macpherson in relation to the report of J. Ross Browne in regards to Mendocino Reservation
His+ reversions Caused in Salmonella typhimurium by different types of ionizing radiation
No full textThe yield of his+ reversions in the Ames Salmonella tester strain TA2638 has been determined for 60Co γ rays, 140 kV X rays, 5.4 keV characteristic X rays, 2.2 MeV protons, 3.1 MeV α particles, and 18 MeV/U Fe ions. Inactivation studies were performed with the same radiations. For both mutation and inactivation, the maximum effectiveness per unit absorbed dose was obtained for the characteristic X rays, which have a dose averaged linear energy transfer (LET) of roughly 10 keV/μm. The ratio of the effectiveness of this radiation to γ rays was 2 for inactivation and about 1.4 for the his+ reversion. For both end points the effectiveness decreases substantially at high LET, i.e., for the α particles and the Fe ions. The composition of the bottom and the top agar was the one recommended by Maron and Ames [Mutat. Res. 113, 173-215 (1983)] for application in chemical mutagenicity tests. The experiments with the less penetrating radiations differed from the usual protocol by utilization of a technique of plating the bacteria on the surface of the top agar. As in an earlier study [Roos et al., Radiat. Res. 104, 102-108 (1985)] greatly enhanced yields of mutations, relative to the spontaneous reversion rate, were obtained in these experiments by performing the irradiations 6 h after plating, which differs from the conventional procedure to irradiate the bacteria shortly after plating
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