5,030 research outputs found
Grinding as an approach to the production of high-strength, dispersion-strengthened nickel-base alloys
Mechanical process produces dispersion-strengthened metal alloys. Power surface contamination during milling is removed by a cleaning method that involves heating thin shapes or partially-compacted milled powder blends in hydrogen to carefully controlled temperature schedules
Magnetic phase diagram of the iron pnictides in the presence of spin-orbit coupling: Frustration between and magnetic phases
We investigate the impact of spin anisotropic interactions, promoted by
spin-orbit coupling, on the magnetic phase diagram of the iron-based
superconductors. Three distinct magnetic phases with Bragg peaks at
and are possible in these systems: one (i.e. orthorhombic)
symmetric stripe magnetic phase and two (i.e. tetragonal) symmetric
magnetic phases. While the spin anisotropic interactions allow the magnetic
moments to point in any direction in the phase, they restrict the
possible moment orientations in the phases. As a result, an interesting
scenario arises in which the spin anisotropic interactions favor a phase,
but the other spin isotropic interactions favor a phase. We study this
frustration via both mean-field and renormalization-group approaches. We find
that, to lift this frustration, a rich magnetic landscape emerges well below
the magnetic transition temperature, with novel , , and mixed
- phases. Near the putative magnetic quantum critical point, spin
anisotropies promote a stable Gaussian fixed point in the renormalization-group
flow, which is absent in the spin isotropic case, and is associated with a
near-degeneracy between and phases. We argue that this frustration
is the reason why most phases in the iron pnictides only appear inside
the phase, and discuss additional manifestations of this frustration in
the phase diagrams of these materials.Comment: 21 pages, 19 figures, published versio
Emergent magnetic degeneracy in iron pnictides due to the interplay between spin-orbit coupling and quantum fluctuations
Recent experiments in iron pnictide superconductors reveal that, as the
putative magnetic quantum critical point is approached, different types of
magnetic order coexist over a narrow region of the phase diagram. Although
these magnetic configurations share the same wave-vectors, they break distinct
symmetries of the lattice. Importantly, the highest superconducting transition
temperature takes place close to this proliferation of near-degenerate magnetic
states. In this paper, we employ a renormalization group calculation to show
that such a behavior naturally arises due to the effects of spin-orbit coupling
on the quantum magnetic fluctuations. Formally, the enhanced magnetic
degeneracy near the quantum critical point is manifested as a stable Gaussian
fixed point with a large basin of attraction. Implications of our findings to
the superconductivity of the iron pnictides are also discussed.Comment: 6 pages, 2 figures, published versio
Enhanced nematic fluctuations near an antiferromagnetic Mott insulator and possible application to high- cuprates
Motivated by the widespread experimental observations of nematicity in
strongly underdoped cuprate superconductors, we investigate the possibility of
enhanced nematic fluctuations in the vicinity of a Mott insulator that displays
N\'eel-type antiferromagnetic order. By performing a strong-coupling expansion
of an effective model that contains both Cu- and O- orbitals on the
square lattice, we demonstrate that quadrupolar fluctuations in the
-orbitals inevitably generate a biquadratic coupling between the spins of
the -orbitals. The key point revealed by our classical Monte Carlo
simulations and large- calculations is that the biquadratic term favors
local stripe-like magnetic fluctuations, which result in an enhanced nematic
susceptibility that onsets at a temperature scale determined by the effective
Heisenberg exchange . We discuss the impact of this type of nematic order on
the magnetic spectrum and outline possible implications on our understanding of
nematicity in the cuprates.Comment: 11 pages, 4 figures; includes Supplemental Material (14 pages, 4
figures
Universal collisionless transport of graphene
The impact of the electron-electron Coulomb interaction on the optical
conductivity of graphene has led to a controversy that calls into question the
universality of collisionless transport in this and other Dirac materials.
Using a lattice calculation that avoids divergences present in previous nodal
Dirac approaches, our work settles this controversy and obtains results in
quantitative agreement with experiment over a wide frequency range. We also
demonstrate that dimensional regularization methods agree, as long as the
scaling properties of the conductivity and the regularization of the theory in
modified dimension are correctly implemented. Tight-binding lattice and nodal
Dirac theory calculations are shown to coincide at low energies even when the
non-zero size of the atomic orbital wave function is included, conclusively
demonstrating the universality of the optical conductivity of graphene.Comment: 4+ pages,4 figures; includes Supplemental Material (18 pages, 2
figures
Production and processing of Cu-Cr-Nb alloys
A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling
Woman in the Mirror; Precious Child of God or Just a Rib?
This thesis entitled, “Woman in the Mirror: Precious Child of God, or Just a Rib?” is based on a request from colleagues to create a curriculum as a companion piece to the Rev. Dr. Kevin Frederick’s curriculum, “Men in the Mirror: Orienting Our Lives Toward a Christ-Centered Masculinity.” The curriculum will be used by pastors and pastoral counselors working with women who struggle with self-esteem and/or are victims of domestic violence. This thesis explores the problem that some women seem to lack a clear understanding of their position in the kingdom of God. Looking at how women understood God, their identity as followers of Jesus Christ, and how they live their faith in their identity, this thesis used qualitative research and a triangulation of a questionnaire, an inventory tool and interviews with women. The results of the research provided the data necessary to create the content for the curriculum
Antechamber facilitates loading and unloading of vacuum furnace
Antechamber facilitates the use of a furnace in which materials are heat treated in a high vacuum or a gas atmosphere. It has a high vacuum pumping system, a means for backfilling with a selected gas, an access door, glove ports, and a motor driven platform
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