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 Timeofflight measurements (1)
 Manganese Alloys (1)
 Nd2Fe17Mn (1)
 Xerography (1)
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 Doping (additives) (1)
 Bond Length (1)
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 Nd2Fe17Si (1)
 Silicon Alloys (1)
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 Nd2Fe17XSix (1)
 Neutron Diffraction (1)
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Articles 1  16 of 16
FullText Articles in Physical Sciences and Mathematics
AngleResolved XRay Circular And Magnetic Circular Dichroisms: Definitions And Applications, Sy Y. Tong, X. Q. Guo, James G. Tobin, George Daniel Waddill
AngleResolved XRay Circular And Magnetic Circular Dichroisms: Definitions And Applications, Sy Y. Tong, X. Q. Guo, James G. Tobin, George Daniel Waddill
Physics Faculty Research & Creative Works
We introduce definitions of angleresolved xray circular dichroism (ARXCD) and magnetic xray circular dichroism (ARMXCD). As defined, the much larger effect of circular dichroism (ARXCD) is separated from the smaller magnetic (ARMXCD) effect. In all materials, ARXCD is zero along mirror planes while nonzero elsewhere. ARMXCD is nonzero only in magnetic materials. The measurement and analysis of ARMXCD allow element specific surface magnetism and surface structure as well as their interrelationship to be studied as functions of the outgoing electron's direction.
Breakdown Of LandauGinzburgWilson Theory For Certain Quantum Phase Transitions, Thomas Vojta, Dietrich Belitz, Rajesh S. Narayanan, Theodore R. Kirkpatrick
Breakdown Of LandauGinzburgWilson Theory For Certain Quantum Phase Transitions, Thomas Vojta, Dietrich Belitz, Rajesh S. Narayanan, Theodore R. Kirkpatrick
Physics Faculty Research & Creative Works
The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the LandauGinzburgWilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective longrange interaction between the spins of the form 1/r^{2d1}. It leads to unusual scaling behavior at the quantum critical point in 1 < d ≤ 3 dimensions, which is determined exactly.
Theory Of The Seebeck Coefficient In Lacro₃ And Related Perovskite Systems, D. B. Marsh, Paul Ernest Parris
Theory Of The Seebeck Coefficient In Lacro₃ And Related Perovskite Systems, D. B. Marsh, Paul Ernest Parris
Physics Faculty Research & Creative Works
We consider the Seebeck coefficient in LaCrO_{3} and related transitionmetaloxide perovskites using a model for electronic conduction based on the electronic structure of the 3d orbitals of the Bsite transitionmetal cations. Relations for the Seebeck coefficient are presented for those perovskite systems in which electronic conduction is through the t_{2g} states of the Bsite transitionmetal cations. High and lowtemperature limits for the Seebeck coefficient are identified for the cases of both strong and weak magnetic coupling between electron spins. In these high and lowtemperature limits, the Seebeck coefficient is determined as a function of carrier concentration. Results are ...
HigherOrder Binding Corrections To The Lamb Shift Of 2p States, Ulrich D. Jentschura, Krzysztof Pachucki
HigherOrder Binding Corrections To The Lamb Shift Of 2p States, Ulrich D. Jentschura, Krzysztof Pachucki
Physics Faculty Research & Creative Works
We present an improved calculation of higherorder corrections to the oneloop selfenergy of 2P states in hydrogenlike systems with small nuclear charge Z. The method is based on a division of the integration with respect to the photon energy into a high and a lowenergy part. The highenergy part is calculated by an expansion of the electron propagator in powers of the Coulomb field. The lowenergy part is simplified by the application of a FoldyWouthuysen transformation. This transformation leads to a clear separation of the leading contribution from the relativistic corrections and removes higherorder terms. The method is applied to ...
Neutron Diffraction Structural Study Of Ce₂Fe₁₇₋ₓGaₓ, H. Luo, Z. Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow
Neutron Diffraction Structural Study Of Ce₂Fe₁₇₋ₓGaₓ, H. Luo, Z. Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow
Physics Faculty Research & Creative Works
Six samples of Ce_{2}Fe_{17x}Ga_{x} with nominal Ga content x equal to 0, 0.3, 0.5, 0.7, 1.0, 2.0 have been studied by powder neutron diffraction at room temperature. Both crystalline and magnetic refinements have been carried out. All six samples adopt the Th_{2}Zn_{17}type rhombohedral structure. The only additional phase found is αiron. Gallium atoms are found to have high affinity for the iron 18h site, and are absent from the 9d and 18f sites. The Ga substitution for Fe leads to an expansion of both the a ...
Relation Between ChargeDipole Interactions And The Sqrt(E)Dependent Mobility In Molecularly Doped Polymers, Paul Ernest Parris
Relation Between ChargeDipole Interactions And The Sqrt(E)Dependent Mobility In Molecularly Doped Polymers, Paul Ernest Parris
Physics Faculty Research & Creative Works
Timeofflight measurements on a wide variety of molecularlydoped polymers reveal carrier mobilities that exhibit an exponential dependence on the square root of the applied electric field. Recent attempts to explain the observed field dependence have focused on the role played by spatial and energetic disorder. It as also been conjectured that the chargedipole interactions often identified as the source of energetic disorder could be of sufficient range to lead to correlations in the energies of neighboring hopping sites. We have analytically explored the effect of such correlations on high field carrier transport in random potentials, and discuss how particular features ...
ChargeDipole Model For The Universal Field Dependence Of Mobilities In Molecularly Doped Polymers, David H. Dunlap, Paul Ernest Parris, Vasudev M. Kenkre
ChargeDipole Model For The Universal Field Dependence Of Mobilities In Molecularly Doped Polymers, David H. Dunlap, Paul Ernest Parris, Vasudev M. Kenkre
Physics Faculty Research & Creative Works
Using the general result that the mobility μ, of charge carriers driven in a spatially correlated random potential by an electric field E can be expressed in terms of the Laplace transform of a particular correlation function related to the random potential, we demonstrate that the exponential dependence of μ on √E universally observed in molecularly doped polymers arises naturally from the interaction of charge carriers with randomly distributed permanent dipoles.
Binary Nucleation Kinetics. Iii. Transient Behavior And Time Lags, Barbara Ellen Wyslouzil, Gerald Wilemski
Binary Nucleation Kinetics. Iii. Transient Behavior And Time Lags, Barbara Ellen Wyslouzil, Gerald Wilemski
Physics Faculty Research & Creative Works
Transient binary nucleation is more complex than unary because of the bidimensionality of the cluster formation kinetics. To investigate this problem qualitatively and quantitatively, we numerically solved the birthdeath equations for vaportoliquid phase transitions. Our previous work [J. Chem. Phys 103, 1137 (1995)] showed that the customary saddle point and growth path approximations are almost always valid in steady state gas phase nucleation and only fail if the nucleated solution phase is significantly nonideal. The current work demonstrates that in its early transient stages, binary nucleation rarely, if ever, occurs via the saddle point. This affects not only the number ...
Neutron Diffraction Studies Of NdₙFeₘ₋ₓ₋_{Y}VₓAl_{Y} [(N,M)=(1,12), (2,17), (3,29)], Z. Hu, William B. Yelon, William Joseph James
Neutron Diffraction Studies Of NdₙFeₘ₋ₓ₋YVₓAlY [(N,M)=(1,12), (2,17), (3,29)], Z. Hu, William B. Yelon, William Joseph James
Physics Faculty Research & Creative Works
Several Nd_{n}Fe_{mxy}V_{x}Al_{y} [(n,m)=(1,12), (2,17), (3,29)] samples were prepared and analyzed using neutron powder diffraction. Rietveld analysis of the neutron diffraction data indicates that the V and Al substituents take those sites with similar environments in all three phases, as observed in our previous study of Tisubstituted compounds. It was confirmed that the diffraction data of the 3:29 compound can be better refined using the A2/m space group than using the P2_{1}/c space group. The SQUID measurements show that all samples have Curie temperatures well ...
Neutron Diffraction And Magnetic Studies Of Rfe₁₂₋ₓTₓC_{Y} (R=Y,Er; T=V,Ti,Mo) Alloys, Z. Hu, William B. Yelon, X. D. Zhang, William Joseph James
Neutron Diffraction And Magnetic Studies Of Rfe₁₂₋ₓTₓCY (R=Y,Er; T=V,Ti,Mo) Alloys, Z. Hu, William B. Yelon, X. D. Zhang, William Joseph James
Physics Faculty Research & Creative Works
RFe_{12x}T_{x}C_{y}, (R=Y,Er; T=V,Ti,Mo) alloys were prepared by rf induction melting and analyzed using neutron powder diffraction and superconducting quantum interference device (SQUID) measurements. Rietveld analysis of the neutron diffraction data indicates that V, Ti, and Mo atoms all prefer the 8i sites. The refined amount of carbon atoms found in the interstitial sites from neutron diffraction data is significantly less than the nominal carbon content. All samples have the easy direction along the c axis. The Er sublattice couples to the Fe sublattice antiferromagnetically. The average Fe site moments range ...
Site Affinity Of Substituents In Nd₂Fe₁₇₋ₓTₓ (T=Cu,Zr,Nb,Ti,V) Alloys, William B. Yelon, Z. Hu, William Joseph James, G. K. Marasinghe
Site Affinity Of Substituents In Nd₂Fe₁₇₋ₓTₓ (T=Cu,Zr,Nb,Ti,V) Alloys, William B. Yelon, Z. Hu, William Joseph James, G. K. Marasinghe
Physics Faculty Research & Creative Works
In order to understand the magnetic properties of the substituted rareearthiron alloys, it is especially important to know the location of the substitutional atoms within the iron lattice. The site distributions of some nontransitionmetal substituents in the substituted Nd_{2}Fe_{17x}T_{x} alloys have previously been reported. Here we report the site distributions of some transitionmetal substituents (Cu,Zr,Nb,Ti,V) in the Nd_{2}Fe_{17x}T_{x} alloys and compare them with those of the nontransitionmetal substituted compounds. Rietveld analysis of neutron powder diffraction data indicates that the nontransitionmetal substituents show very similar site affinity ...
FineStructure Effect For (E,2e) Collisions, Don H. Madison, V. D. Kravtsov, Stephenie J. Jones, Robert P. Mceachran
FineStructure Effect For (E,2e) Collisions, Don H. Madison, V. D. Kravtsov, Stephenie J. Jones, Robert P. Mceachran
Physics Faculty Research & Creative Works
For the case of inelastic electronatom scattering, it has been known for some time that significant spin effects may be observed even if spindependent forces on the projectile can be ignored. These spin effects result from the Pauli principle and this phenomenon has become known as the finestructure effect. Recently, the question of whether or not these same types of effects should be observed for atomic ionization has been considered and the initial indications are that significant spin asymmetries can also be expected for atomic ionization if the final ion satisfies LS coupling and the final J state of the ...
Critical Behavior Of A Quantum Spherical Model In A Random Field, Thomas Vojta, Michael Schreiber
Critical Behavior Of A Quantum Spherical Model In A Random Field, Thomas Vojta, Michael Schreiber
Physics Faculty Research & Creative Works
We consider the influence of a quenched random field on the critical behavior of a quantum spherical model at the zerotemperature quantum phase transition. We find a complete solution of the model for arbitrary translationally invariant pair interactions. It turns out that the critical behavior for zero as well as finite temperatures is dominated by static random field fluctuations rather than by quantum or thermal fluctuations. Therefore the critical behavior close to the zerotemperature quantum phase transition is identical to that close to a finitetemperature transition. The system does not show a crossover from quantum to classical behavior.
Quantum Version Of A Spherical Model: Crossover From Quantum To Classical Critical Behavior, Thomas Vojta
Quantum Version Of A Spherical Model: Crossover From Quantum To Classical Critical Behavior, Thomas Vojta
Physics Faculty Research & Creative Works
We investigate a quantum version of the spherical model which is obtained from the classical BerlinKac spherical model by a simple canonical quantization scheme. We find a complete solution of the model for shortrange as well as for longrange interactions. At finite temperatures the critical behavior is the same as in the classical spherical model whereas at zero temperature we find a quantum phase transition characterized by new critical exponents. Based on a functionalintegral representation of the partition function the free energy of the model is shown to be equivalent to that of the nonlinear σ model in the limit ...
EffectiveMedium Theory For The ElectricField Dependence Of The Hopping Conductivity Of Disordered Solids, Paul Ernest Parris, B. D. Bookout
EffectiveMedium Theory For The ElectricField Dependence Of The Hopping Conductivity Of Disordered Solids, Paul Ernest Parris, B. D. Bookout
Physics Faculty Research & Creative Works
We derive a general effectivemedium theory for describing biased diffusion on a bonddisordered lattice in the presence of an external driving field. In our theory, the effective medium associated with a disordered ddimensional lattice is characterized, for each value of the applied field, by 2d independent parameters describing, respectively, the net drift velocity v_{v} and the diffusion constant D_{vv} describing the spread of a carrier packet about its mean value, for each of the d crystal axes. The theory correctly predicts the velocity transition occurring in an exactly soluble model studied by Derrida and, in contrast to other ...
Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓTₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James
Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓTₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James
Physics Faculty Research & Creative Works
We have carried out neutron and magnetic studies on Nd_{2}Fe_{17x}T_{x} (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by ...