The Fermi hole and the exchange parameter inXαtheory

1976 ◽  
Vol 14 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. S. Gopinathan ◽  
M. A. Whitehead ◽  
R. Bogdanović
Keyword(s):  
Exchange Parameter ◽  
Fermi Hole

Twinned olivenite from Cap Garonne, Mine du Pradet – structure and magnetic behavior

2020 ◽  
Vol 235 (1-2) ◽  
pp. 7-13
Author(s):  
Jutta Kösters ◽  
Christian Paulsen ◽  
Frank Stegemann ◽  
Birgit Heying ◽  
Valérie Galéa-Clolus ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystals ◽  
Cluster Model ◽  
Spin Exchange ◽  
Magnetic Behavior ◽  
Exchange Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Cluster ◽  
Antiferromagnetic Spin

AbstractSystematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/kB = 157(3) K.

The origins of the colours of natural yellow, blue, and green sapphires

1972 ◽  
Vol 25 (7) ◽  
pp. 1371 ◽  
Author(s):  
J Ferguson ◽  
PE Fielding
Keyword(s):  
Temperature Dependence ◽  
Absorption Spectra ◽  
Excited States ◽  
Exchange Parameter ◽  
Nearest Neighbour ◽  
Electronic Excitations ◽  
Heisenberg Exchange ◽  
Synthetic Crystals

An analysis of the absorption spectra of natural yellow sapphires shows that the absorption is due to single Fe3+ ions and pairs of ions Fe3+-O2--Fe3+. Assignments of all levels from the 4G, 4P, and 4D have been made as well as four simultaneous electronic excitations of a pair of ions. The temperature dependence of the intensity of the pair absorption shows that one pair is mainly involved, probably the fourth- nearest neighbour pair. The value of the Heisenberg exchange parameter (J Sa. Sb) lies in the range 30-40 K. Estimates of this parameter for various excited states have been made. Synthetic yellow sapphires have spectra which duplicate the natural specimens. Blue and green natural sapphires have, in addition to the bands present in the spectra of yellow sapphires, spectra with bands at 17800 (┴C), 14200 (//c), 11500 (┴C), and 10000 om-1 (//c). The first two can be linked to Fe,Ti pairs and the evidence favours the nearest neighbour pair Ti4+-O2?Fe2+ for the 17800 cm-1 band and possibly the first neighbour pair for the 14200 cm-1 band. The second two can be produced in synthetic crystals by growth from fluoride-containing flux and the evidence supports an explanation involving second-nearest neighbour pairs Fe2+- O2--Fe3+ for the 11500 cm-1 absorption and first neighbours for the 10000 om-1 absorption.

Origin of Hund’s multiplicity rule in singly excited helium: Existence of a conjugate Fermi hole in the lower spin state

2011 ◽  
Vol 83 (3) ◽  
Author(s):  
Tokuei Sako ◽  
Josef Paldus ◽  
Atsushi Ichimura ◽  
Geerd H. F. Diercksen
Keyword(s):  
Spin State ◽  
Lower Spin ◽  
Fermi Hole ◽  
Excited Helium ◽  
Lower Spin State

scholarly journals The complexity-stability hypothesis in plant gas exchange under water deficit

2005 ◽  
Vol 17 (4) ◽  
pp. 363-373 ◽  
Author(s):  
Gustavo M. Souza ◽  
Steven M Pincus ◽  
José Alberto F. Monteiro
Keyword(s):  
Gas Exchange ◽  
Water Deficit ◽  
Temporal Dynamics ◽  
Approximate Entropy ◽  
Exchange Parameter ◽  
Gas Exchange Parameters ◽  
Gas Exchanges ◽  
Respiratory Dynamics ◽  
Net Assimilation ◽  
Exchange Parameters

We hypothesized that more complex, i.e. irregular, temporal dynamics and a more interconnected overall network supports greater stability to gas exchange parameters (herein, CO2 net assimilation and transpiration) in plants under water deficit. To test this hypothesis two genotypes of Phaseolus vulgaris were subjected to a period of absence of irrigation, and subsequent rewatering to achieve recovery. Gas exchanges parameters were measured each 10 s during 6 h to obtain time series to evaluate complexity by Approximate Entropy (ApEn) calculations, and network connectance in each water regime. Notably, the Jalo Precoce genotype showed significantly more stability than the Guarumbé genotype under system perturbation, coincident with greater irregularity in each gas exchange parameter and greater overall connectance for Jalo Precoce. This conclusion is consistent with other observations of greater homeostasis in more complex networks, seen in broad contexts such as cardiac rhythms and respiratory dynamics

Structure of the Fermi hole at surfaces

1988 ◽  
Vol 37 (2) ◽  
pp. 745-754 ◽  
Author(s):  
Manoj K. Harbola ◽  
Viraht Sahni
Keyword(s):  
Fermi Hole

MAGNETISATION AND MAGNETORESISTANCE OF Ho2Co17

1993 ◽  
Vol 07 (01n03) ◽  
pp. 802-805
Author(s):  
F.E. KAYZEL ◽  
R.J. RADWAŃSKI ◽  
L.T. TAI ◽  
K. BAKKER ◽  
J.J.M. FRANSE
Keyword(s):  
Magnetic Structure ◽  
Magnetization Curve ◽  
High Field ◽  
Spin Exchange ◽  
Exchange Parameter ◽  
Hexagonal Cell ◽  
Abrupt Decrease ◽  
Single Crystalline ◽  
Easy Direction ◽  
Transition Field

High field magnetisation measurements up to 38 T have been performed on a newly grown single-crystalline Ho2Co17 sample along the main crystallographic directions of the hexagonal cell. The magnetization curve along the easy direction (b-axis) exhibits a metamagnetic-like transition at 23.6 T whereas for the a-axis a similar transition occurs at 31.4 T. The transitions are extremely sharp - much sharper than in previously grown crystals. The transitions are understood as a moment-flip transition associated with the formation of a non-collinear magnetic structure in this ferrimagnetic compound. From the transition-field value the 3d-4f spin-exchange parameter has been derived. Both of these transitions are seen in the magnetoresistance as an abrupt decrease of the resistance.

SPECIFIC HEAT OF UPd2Al3

1993 ◽  
Vol 07 (01n03) ◽  
pp. 38-41 ◽  
Author(s):  
R. J. RADWAŃSKI ◽  
J. J. M. FRANSE
Keyword(s):  
Magnetic Properties ◽  
Energy Level ◽  
Specific Heat ◽  
Ground State ◽  
Exchange Parameter ◽  
State Function ◽  
Hexagonal Symmetry ◽  
Energy Level Scheme ◽  
Schottky Type ◽  
Good Agreement

Particularities in the specific heat of UPd 2 Al 3, a λ-type of peak with a maximum at 14.5 K and a Schottky-type of peak with a broad maximum at 55 K, has been attributed to the 5f-subsystem of the U atoms. The U-5f contribution has been found to be described surprisingly well within a single-ion Hamiltonian that includes the charge multipolar (CMP) interactions and the antiferromagnetic (AF) exchange interaction between the U 3+ ions. The AF exchange parameter and the full set of the CMP parameters associated with the hexagonal symmetry have been evaluated. The energy-level scheme (ELS) of this Kramers ion is constructed. The ground-state function Γ8 of the 5f 3 electrons is highly anisotropic. This state results from higher-order charge multipolar interactions. Magnetic properties resulting from this scheme including the metamagnetic-like transition at 18 T, the strongly-reduced value for the U-ion moment and its field dependence are found to be in good agreement with experimental observations.

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