scholarly journals Magnetic Structure of CoO

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1513
Author(s):  
Ekkehard Krüger
Keyword(s):  
Fermi Level ◽  
Magnetic Structure ◽  
Mott Insulator ◽  
Spin Axis ◽  
Monoclinic Distortion ◽  
Spin Arrangement ◽  
Oxygen Atoms

The paper reports evidence that the multi-spin-axis magnetic structure proposed in 1964 by van Laar is realized in antiferromagnetic CoO. This tetragonal spin arrangement produces both the strong tetragonal and the weaker monoclinic distortion experimentally observed in this material. The monoclinic distortion is proposed to be a “monoclinic-like” distortion of the array of the oxygen atoms, comparable with the rhombohedral-like distortion of the oxygen atoms recently proposed to be present in NiO and MnO. The monoclinic-like distortion has no influence on the tetragonal magnetic structure, which is generated by a special nonadiabatic atomic-like motion of the electrons near the Fermi level. It is argued that it is this atomic-like motion that qualifies CoO to be a Mott insulator.

scholarly journals Der Antiferromagnetismus des Ferritins bei Messungen der magnetischen Suszeptibilität im Temperaturbereich von 4,2 bis 300°K

1965 ◽  
Vol 20 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Georg Schoffa
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Structure ◽  
Magnetic Moment ◽  
Exchange Constant ◽  
Antiferromagnetic Exchange ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Temperature Range ◽  
Experimental Values ◽  
Oxygen Atoms

Measurements of magnetic susceptibility in the temperature range 4.2-300°K show that ferritin is antiferromagnetic with a Néel temperature of 20° ± 3°K. The theory of J. S. SMART for antiferromagnetic exchange between iron atoms clustered in groups of two (“isolated clusters”) gives the best agreement between theoretical and experimental values. The antiferromagnetic exchange constant is J/k=- 4.8 (°K). Reduced magnetic moment for µeff =3.85 μB is due to the transfer of two electrons from oxygen atoms to ferric atoms caused on the cation-anion-cation superexchange. Some models of superexchange are discussed. Antiferromagnetism and superexchange are possibly caused on the cubic magnetic structure of iron-oxygen micelles in ferritin.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Electronic States near the Fermi Level in the Antiferromagnetic and Ferromagnetic Spinels of Zn 1− x Cu x Cr 2 Se 4 ; 0.0 ≤ x ≤ 1.0

2002 ◽  
Vol 75 (4-5) ◽  
pp. 359-371
Author(s):  
M. Hidaka ◽  
N. Tokiwa ◽  
M. Yoshimura ◽  
H. Fujii ◽  
Jae-Young Choi ◽  
...  
Keyword(s):  
Fermi Level ◽  
Electronic States

Catalytic CO Oxidation on Unreconstructed Cu(110) by Reactive As-Adsorbed Oxygen Atoms below 230 K

1996 ◽  
Vol 100 (3) ◽  
pp. 1048-1054 ◽  
Author(s):  
Tsuyoshi Sueyoshi ◽  
Takehiko Sasaki ◽  
Yasuhiro Iwasawa
Keyword(s):  
Co Oxidation ◽  
Adsorbed Oxygen ◽  
Catalytic Co Oxidation ◽  
Oxygen Atoms

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

1H-NMR study of Mott insulator κ -(ET)2Cu2(CN)3with isotropic triangular lattice

2004 ◽  
Vol 114 ◽  
pp. 377-378 ◽  
Author(s):  
Y. Shimizu ◽  
K. Miyagawa ◽  
K. Oda ◽  
K. Kanoda ◽  
M. Maesato ◽  
...  
Keyword(s):  
1H Nmr ◽  
Triangular Lattice ◽  
Mott Insulator ◽  
Nmr Study
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