6,959 research outputs found
An {\it ab initio} study of the magnetic and electronic properties of Fe, Co, and Ni nanowires on Cu(001) surface
Magnetism at the nanoscale has been a very active research area in the past
decades, because of its novel fundamental physics and exciting potential
applications. We have recently performed an {\it ab intio} study of the
structural, electronic and magnetic properties of all 3 transition metal
(TM) freestanding atomic chains and found that Fe and Ni nanowires have a giant
magnetic anisotropy energy (MAE), indicating that these nanowires would have
applications in high density magnetic data storages. In this paper, we perform
density functional calculations for the Fe, Co and Ni linear atomic chains on
Cu(001) surface within the generalized gradient approximation, in order to
investigate how the substrates would affect the magnetic properties of the
nanowires. We find that Fe, Co and Ni linear chains on Cu(001) surface still
have a stable or metastable ferromagnetic state. When spin-orbit coupling (SOC)
is included, the spin magnetic moments remain almost unchanged, due to the
weakness of SOC in 3 TM chains, whilst significant orbital magnetic moments
appear and also are direction-dependent. Finally, we find that the MAE for Fe,
and Co remains large, i.e., being not much affected by the presence of Cu
substrate.Comment: 4 pages, 2 figure
A method to define a minimum-phase transfer function within the bounded region of phase-gain specifications
Method to define minimum phase transfer function within bounded region of phase gain specifications at several discrete frequencie
Magnetic moment and magnetic anisotropy of linear and zigzag 4{\it d} and 5{\it d} transition metal nanowires: First-principles calculations
An extensive {\it ab initio} study of the physical properties of both linear
and zigzag atomic chains of all 4 and 5 transition metals (TM) within the
GGA by using the accurate PAW method, has been carried out. All the TM linear
chains are found to be unstable against the corresponding zigzag structures.
All the TM chains, except Nb, Ag and La, have a stable (or metastable) magnetic
state in either the linear or zigzag or both structures. Magnetic states appear
also in the sufficiently stretched Nb and La linear chains and in the largely
compressed Y and La chains. The spin magnetic moments in the Mo, Tc, Ru, Rh, W,
Re chains could be large (1.0 /atom). Structural transformation
from the linear to zigzag chains could suppress the magnetism already in the
linear chain, induce the magnetism in the zigzag structure, and also cause a
change of the magnetic state (ferromagnetic to antiferroamgetic or vice verse).
The calculations including the spin-orbit coupling reveal that the orbital
moments in the Zr, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir and Pt chains could be
rather large (0.1 /atom). Importantly, large magnetic anisotropy
energy (1.0 meV/atom) is found in most of the magnetic TM chains,
suggesting that these nanowires could have fascinating applications in
ultrahigh density magnetic memories and hard disks. In particular, giant
magnetic anisotropy energy (10.0 meV/atom) could appear in the Ru, Re,
Rh, and Ir chains. Furthermore, the magnetic anisotropy energy in several
elongated linear chains could be as large as 40.0 meV/atom. A
spin-reorientation transition occurs in the Ru, Ir, Ta, Zr, La and Zr, Ru, La,
Ta and Ir linear chains when they are elongated. Remarkably, all the 5 as
well as Tc and Pd chains show the colossal magnetic anisotropy (i.e., it is
impossible to rotate magnetization into certain directions). Finally, the
electronic band structure and density of states of the nanowires have also been
calculated in order to understand the electronic origin of the large magnetic
anisotropy and orbital magnetic moment as well as to estimate the conduction
electron spin polarization.Comment: To appear in Phys. Rev.
Review of Fouseki, K. 2015. Dispute Management in Heritage Conservation: The Case of in situ Museums.
Career mobility in a global era: advances in managing expatriation and repatriation
The surge of interest in expatriation and repatriation within the broader discourse on labor mobility of professionals and high-skilled labor, human capital development and the theory and practice of people management, serves as the backdrop to this paper. We propose that expatriation and repatriation be framed in the context of global careers and embedded in the wider social-economic environment of globalization through the lens of a career ecosystem theory. We chart the evolution of scholarly publications on career mobility over the past four decades and highlight current trends, in particular the emergence of self-initiated expatriation as a pivotal change in the direction of expatriation studies and derived practice. We assess the rigor of empirical findings, weigh theoretical underpinnings, offer a research agenda for future research and outline managerial implications
The Effect of Ultrafiltration on Protein Quality of Skimmilk and Cottage Cheese
Protein quality in freeze-dried skimmilk (SM), regular cottage cheese (RCC), retentate (Ret) and cottage cheese made from ultrafiltrated skimmilk (UFCC) were evaluated by chemical (amino acid score) and biological methods. Biological evaluation was at 5, 8 and 11% protein level in growing rats by measuring biological value (BV), net protein utilization (NPU) and nitrogen efficiency for growth (NEG) over a 14-day period. A 28-day protein efficiency ratio (PER) was determined on the same products at 10% protein level. Effects of added lactose on PER of retentate, regular and UFCC were also evaluated. The most limiting amino acids were cystine + methionine. Amino acid score for Animal Nutrition Research Council (ANRC) reference casein, SM, RCC, Ret and UFCC was 0.72, 0.91, 0.87, 0.91 and 0.98 respectively according to Food and Agricultural Organization/World Health Organization (FAO/WHO) pattern and 0.45, 0.56, 0.54, 0.57 and 0.61 respectively according to whole egg pattern. PER was 2.7, 3.0, 2.7, 3.1 and 2.8 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. PER for retentate and skimmilk were significantly different from the cottage cheese. No significant difference in protein quality was obtained when the products were fed at 5, 8 and 11% levels. Average BV was 93, 91, 91, 95 and 94 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. Average NPU was 87, 84, 83, 85 and 85 for ANRC reference casein, SM. RCC, Ret and UFCC respectively. Average NEG values were 66, 73, 70 77 and 73 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. PER values were 2.7, 3.0, 2.7, 3.1 and 2.8 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. Addition of lactose to a level equal to that in skimmilk reduced the PER value of RCC, Ret and UFCC by about 4%, 6% and 4% respectively. Though no significant difference in protein quality of the products were obtained, there was a tendency of ultrafiltration to increase protein quality
Tunable temperature induced magnetization jump in a GdVO3 single crystal
We report a novel feature of the temperature induced magnetization jump
observed along the a-axis of the GdVO3 single crystal at temperature TM = 0.8
K. Below TM, the compound shows no coercivity and remanent magnetization
indicating a homogenous antiferromagnetic structure. However, we will
demonstrate that the magnetic state below TM is indeed history dependent and it
shows up in different jumps in the magnetization only when warming the sample
through TM. Such a magnetic memory effect is highly unusual and suggesting
different domain arrangements in the supposedly homogenous antiferromagnetic
phase of the compound.Comment: 17 pages, 8 Figure
Magnetic anisotropy and spin-spiral wave in V, Cr and Mn atomic chains on Cu(001) surface: First principles calculations
Recent ab intio studies of the magnetic properties of all 3d transition
metal(TM) freestanding atomic chains predicted that these nanowires could have
a giant magnetic anisotropy energy (MAE) and might support a spin-spiral
structure, thereby suggesting that these nanowires would have technological
applicationsin, e.g., high density magnetic data storages. In order to
investigate how the substrates may affect the magnetic properties of the
nanowires, here we systematically study the V, Cr and Mn linear atomic chains
on the Cu(001) surface based on the density functional theory with the
generalized gradient approximation. We find that V, Cr, and Mn linear chains on
the Cu(001) surface still have a stable or metastable ferromagnetic state.
However, the ferromagnetic state is unstable against formation of a
noncollinear spin-spiral structure in the Mn linear chains and also the V
linear chain on the atop sites on the Cu(001) surface, due to the frustrated
magnetic interactions in these systems. Nonetheless, the presence of the
Cu(001) substrate does destabilize the spin-spiral state already present in the
freestanding V linear chain and stabilizes the ferromagnetic state in the V
linear chain on the hollow sites on Cu(001). When spin-orbit coupling (SOC) is
included, the spin magnetic moments remain almost unchanged, due to the
weakness of SOC in 3d TM chains. Furthermore, both the orbital magnetic moments
and MAEs for the V, Cr and Mn are small, in comparison with both the
corresponding freestanding nanowires and also the Fe, Co and Ni linear chains
on the Cu (001) surface.Comment: Accepted for publication in J. Phys. D: Applied Physic
Resonant Subband Landau Level Coupling in Symmetric Quantum Well
Subband structure and depolarization shifts in an ultra-high mobility
GaAs/Al_{0.24}Ga_{0.76}As quantum well are studied using magneto-infrared
spectroscopy via resonant subband Landau level coupling. Resonant couplings
between the 1st and up to the 4th subbands are identified by well-separated
anti-level-crossing split resonance, while the hy-lying subbands were
identified by the cyclotron resonance linewidth broadening in the literature.
In addition, a forbidden intersubband transition (1st to 3rd) has been
observed. With the precise determination of the subband structure, we find that
the depolarization shift can be well described by the semiclassical slab plasma
model, and the possible origins for the forbidden transition are discussed.Comment: 4 pages, 2 figure
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