VOLUME DEPENDENCE OF VANADIUM MAGNETISM

1993 ◽  
Vol 07 (24n25) ◽  
pp. 1611-1618
Author(s):  
M.E. ELZAIN
Keyword(s):  
Crystal Size ◽  
Local Density ◽  
Magnetic Hyperfine Field ◽  
Local Magnetic Moment ◽  
General Shape ◽  
First Order ◽  
Atom Clusters ◽  
Discrete Variational Method ◽  
Spin Polarized ◽  
Local Properties

The first principle discrete variational method in the spin polarized local density approximation is used to calculate the local properties of 15 atom clusters representing variable crystal size bcc vanadium. Four distinct magnetic configurations are recognized as the lattice constant varies from 5.4 to 8.4 (a.u). At the lowest end, the clusters are paramagnetic (PM) whereas at the upper end, clusters are ferromagnetic (FM). In between, antiferromagnetic couplings prevail. The local magnetic moment increases, in a fashion not unlike second order transitions, from zero in the PM range to nonzero in the AFM region. Transitions between other phases are first order. The systematics of these transitions are ascribed to the general shape of the density of states. The contact magnetic hyperfine field, charge density, and 3d partial occupations at the central sites are also calculated.

Electronic Structure and Magnetic State of TiSe2 Doped with Cr by Means of Intercalation or Substitution of Ti

2010 ◽  
Vol 168-169 ◽  
pp. 380-383 ◽  
Author(s):  
A.S. Shkvarin ◽  
A.I. Merentsov ◽  
Y.M. Yarmoshenko ◽  
N.A. Skorikov ◽  
A.N. Titov
Keyword(s):  
Magnetic State ◽  
Local Density ◽  
Local Magnetic Moment ◽  
Host Lattice ◽  
Local Density Of States ◽  
Half Metallic ◽  
Spin Polarized ◽  
Band Spectra ◽  
Grown Structure ◽  
Good Agreement

Solid solutions 1T-CrxTi1-xSe2 (x = 0-0,83) were synthesized. Single crystals in the concentration range x = 0-0.69 were grown. Structure of these materials was studied on single- and polycrystalline samples. It was determined that chromium atoms substitute for titanium atoms in the TiSe2 host lattice. XPS measurements of the core levels together with the resonance valence band spectra of the 1T-CrxTi1-xSe2, as well as absorption spectra of Ti and Cr were performed. According to the experimental XAS data and multiplet atomic calculation, titanium and chromium atoms have oxidation numbers of +4 and +3, respectively. The local magnetic moment of about 3 eV is detected at Cr atoms. A transition into the spin glass state is observed. The modeling calculations of chromium local density of states were carried out. These results are in a good agreement with the experimental ones and suggest that 3d density of electronic states of chromium that substitutes for titanium in the host lattice is spin polarized and has a half-metallic character.

THE MAGNETISM OF 3D IMPURITIES IN ALKALI METALS

1995 ◽  
Vol 09 (26) ◽  
pp. 3421-3428
Author(s):  
M. E. ELZAIN ◽  
A. A. YOUSIF
Keyword(s):  
Magnetic Moment ◽  
Alkali Metals ◽  
Local Density ◽  
Magnetic Hyperfine Field ◽  
Local Magnetic Moment ◽  
Exchange Splitting ◽  
Magnetic Exchange ◽  
Alkali Atoms ◽  
Positive Valence ◽  
3D Impurities

Cluster calculation of the spin local magnetic moment of Fe in alkali metals is performed. A large Fe moment is retained, independent of the cluster size, even under relatively large compressions. The Fe 3d majority sub-band for both E g and T 2g symmetries are full, indicating a larger magnetic exchange splitting than the crystal field, as has been confirmed by direct computation. The 3d local density of states at the Fe site is found to consist of a single narrow, structureless peak independent of the alkali matrix; however, a small split appears in the minority sub-band in the case of Li and under compression in other metals. The bond order between the 3d atom and the neighboring alkali atoms is found to be vanishingly small for the majority electrons whereas the minority electrons retain a large value. The magnetic hyperfine field at the Fe site, due to the spin contact term, is found to be positive in spite of the large local moment. This is attributed to the cancellation resulting from the large positive valence contribution. The local magnetic moment and exchange splitting at 3d impurities in Na show a maximum at Cr and their ratio, which gives the exchange integral, increases from about 0.7 eV /µ B at Sc to about 0.9 eV /µ B at Ni. The Stoner type criterion is consistent with the retained local magnetic moment.

scholarly journals Magnetism in Iron-Zirconium Systems

1996 ◽  
Vol 1 (1) ◽  
pp. 47
Author(s):  
M.E. Elzain ◽  
A.D. Al-Yousif ◽  
A.M. Gismelseed
Keyword(s):  
Hyperfine Field ◽  
Charge Density ◽  
Magnetic Moment ◽  
Local Density ◽  
Occupation Number ◽  
Zirconium Alloys ◽  
Local Magnetic Moment ◽  
Interstitial Site ◽  
Discrete Variational Method ◽  
Contact Charge Density

The discrete variational method is used to solve the Khon-Sham equation in the spin-polarized local density approximation for Fe-Zr and Fe-Zr-H clusters, representing iron-zirconium and hydrogenated iron-zirconium alloys. The local  magnetic moment and hyperfine field at the Fe site were found to decrease, whereas the contact charge density and occupation number were found to increase with Zr contents. The Zr site in clusters with high Fe contents acquires a negative magnetic moment. When H is trapped at an interstitial site next-neighboring an Fe atom, the magnetic moment and hyperfine field are enhanced, while the contact charge density is reduced. ‘The opposite occurs when H occupies a neighboring interstitial site to Fe. For Zr atoms the local magnetic moment is found to become less negative with H at the neighboring position. We conclude from this calculation that H is trapped in Fe-Zr systems at positions which are nearest to Zr and next-nearest to Fe atoms.

Magnetic Properties of Embedded Rh Clusters in Ni Matrix

1995 ◽  
Vol 384 ◽  
Author(s):  
Zhi-Qiang Li ◽  
Yuichi Hashi ◽  
Jing-Zhi Yu ◽  
Kaoru Ohno ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Functional Formalism ◽  
Rhodium Clusters ◽  
Spin Polarized ◽  
Local Density Functional

ABSTRACTThe electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

Electronic bonding characteristics of hydrogen in bcc iron: Part I. Interstitials

1996 ◽  
Vol 11 (9) ◽  
pp. 2206-2213 ◽  
Author(s):  
Yoshio Itsumi ◽  
D. E. Ellis
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Lattice Relaxation ◽  
Experimental Result ◽  
Functional Formalism ◽  
Discrete Variational Method ◽  
Bcc Iron ◽  
Bond Strengths ◽  
Bonding Characteristics ◽  
Structure Calculations

Electronic structure calculations were carried out for bcc iron (Fe) clusters with or without hydrogen (H), and also involving a vacancy, using the self-consistent Discrete Variational method (DV-Xα) within the local density functional formalism. Bonding characteristics investigated show the following: (i) Interstitial H notably decreases interatomic Fe–Fe bond strengths, but acts over a small distance (within 0.3 nm). (ii) In the perfect Fe lattice field, interstitial H feels a repulsive force at any site. As a result of lattice relaxation, volume expansion may be expected. (iii) H in combination with a vacancy prefers a position shifted from the octahedral site toward the vacancy. This is fairly consistent with an experimental result.

scholarly journals Magnetic Collapse and the Behavior of Transition Metal Oxides: FeO at High Pressures

1997 ◽  
Vol 499 ◽  
Author(s):  
R. E. Cohen ◽  
Y. Fei ◽  
R. Downs ◽  
I. I. Mazin ◽  
D. G. Isaak
Keyword(s):  
Transition Metal Oxides ◽  
High Pressures ◽  
Local Density ◽  
Hexagonal Phase ◽  
Spin Transition ◽  
Generalized Gradient ◽  
Augmented Plane Wave ◽  
First Order ◽  
First Order Transition ◽  
Linearized Augmented Plane Wave

ABSTRACTLinearized augmented plane wave (LAPW) results are presented for FeO at high pressures using the Generalized Gradient Approximation (GGA) to study the high-spin low-spin transition previously predicted by LAPW with the Local Density Approximation (LDA) and Linear Muffin Tin Orbital (LMTO-ASA) methods within the GGA. We find a first-order transition at a pressure of about 105 GPa for the cubic lattice, consistent with earlier LAPW results, but much lower than obtained with the LMTO. The results are generally consistent with recent Mössbauer experiments that show a transition at about 100 GPa. We also discuss the origin of the transition, and show that it is not due to electrostatic crystal-field effects, but is rather due to hybridization and band widening with pressure. Examination of experimental data and computations suggest that the high pressure hexagonal phase of FeO is likely a polytype between the B8 NiAs and anti-B8 AsNi structures. The former is predicted to be an antiferromagnetic metal, and the latter an antiferromagnetic insulator. Implications for geophysics are discussed.

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