Crystal Structure Dependence of Antiferromagnetic Coupling in FE/SI Multilayers

ABSTRACTRecent reports of temperature dependent antiferromagnetic coupling in Fe/Si multilayers have motivated the generalization of models describing magnetic coupling in metal/metal multilayers to metal/insulator and metal/semiconductor layered systems. Interesting dependence of the magnetic properties on layer thickness and temperature are predicted. We report measurements that show the antiferromagnetic (AF) coupling observed in Fe/Si multilayers is strongly dependent on the crystalline coherence of the silicide interlayer. Electron diffraction images show the silicide interlayer has a CsCl structure. It is not clear at this time whether the interlayer is a poor metallic conductor or a semiconductor so the relevance of generalized coupling theories is unclear.

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Rules for Understanding and Designing Novel Molecule-Based Rare-Earth Magnetic Compounds

MRS Proceedings ◽

10.1557/proc-755-dd1.6 ◽

2002 ◽

Vol 755 ◽

Cited By ~ 4

Author(s):

Lindsay E. Roy ◽

Timothy Hughbanks

Keyword(s):

Rare Earth ◽

Perturbation Methods ◽

Magnetic Coupling ◽

Model System ◽

Qualitative Approach ◽

Antiferromagnetic Coupling ◽

Ferromagnetic Coupling ◽

Magnetic Ground State ◽

Metal Metal ◽

Low Dimensional

ABSTRACTResults of SDFT calculations were used to construct and check features of a generally applicable qualitative approach to understanding magnetic coupling in rare-earth-rich compounds. Using fragments based on structures of metal-rich lanthanide compounds, we have investigated molecular and low-dimensional extended structures, including Gd3I6(OPH3)12, Gd6I12Co(OPH3)6, and Gd2Cl3. Open-d-shell clusters facilitate strong ferromagnetic coupling whereas in the closed-d-shell systems prefer antiferromagnetic coupling. The f-d exchange interaction, mediated by spin polarization of both filled and partially-filled metal-metal bonding orbitals, was described for the model system Gd3I6(OPH3)12n+ using basic perturbation methods. This method has been successful for predicting the magnetic ground state for models of Gd[Gd6I12Fe] and Gd2Cl3.

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Synthese, Magnetismus und Kristallstruktur des trinuklearen Cu(II)-Komplexes [(LCu)2Cu(H2O)](ClO4)2 · 2 H2O (L = 4,7-Bis(2-hydroxybenzyl)-1-oxa-4,7-diazacyclononan) / Synthesis, Magnetism and Crystal Structure of the Trinuclear Cu(II)-Complex [(LCu)2Cu(H2O)](ClO4)2 · 2H2O (L = 4,7-Bis(2-hydroxybenzyl)-1-oxa-4,7-diazacyclononane)

Zeitschrift für Naturforschung B ◽

10.1515/znb-1991-1106 ◽

1991 ◽

Vol 46 (11) ◽

pp. 1489-1495 ◽

Cited By ~ 2

Author(s):

Claus Flaßbeck ◽

Karl Wieghardt ◽

Bernhard Nuber ◽

Johannes Weiss

Keyword(s):

Crystal Structure ◽

Magnetic Susceptibility ◽

Ground State ◽

Acetone Solution ◽

Antiferromagnetic Coupling ◽

Temperature Dependent

The trinuclear copper(II) complex [(LCu)2Cu(H2O)](ClO4)2·2H2O (L = 4,7-bis(2-hydroxybenzyl)-1-oxa-4,7-diazacyclononane) has been synthesized and its crystal structure has been determined. From temperature dependent magnetic susceptibility measurements strong intramolecular antiferromagnetic coupling of the spins has been detected yielding an S = 1/2 ground state. The trinuclear species dimerizes in acetone solution to yield {[(CuL)2Cu]2}(ClO4)4 which has an S = O ground state.

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Crystal Structure and Magnetic Properties of a (μ-Hydroxo)(μ-acetato) Dicopper(II) Complex

Zeitschrift für Naturforschung B ◽

10.1515/znb-2000-0702 ◽

2000 ◽

Vol 55 (7) ◽

pp. 561-566 ◽

Cited By ~ 8

Author(s):

E. Kavlakoglu ◽

A. Elmali ◽

Y. Elerman ◽

H. Fuess

Keyword(s):

Crystal Structure ◽

Magnetic Properties ◽

Magnetic Susceptibility ◽

Antiferromagnetic Coupling ◽

Monoclinic Space Group ◽

Helium Temperature ◽

Temperature Dependent ◽

Bridging Ligands ◽

Square Planar ◽

Super Exchange Interaction

[Cu2(L)(O2CMe)] · H2O (L = 1,3-Bis(2-Hydroxy-1-napthylideneamino)propan-2-ol) was synthesized and its crystal structure determined. (C27H23N2O5Cu2).H2O , monoclinic, space group P21/c, a = 11.795(3), b = 17.988(5), c = 12.005(6) Å, β = 109.99(3)°, V = 2393(2) Å3, Z = 4. Two copper(II) ions in a square-planar coordination are bridged by alkoxide and acetate oxygen atoms to form a dinuclear unit. The metal coordination sphere is four-coordinate, planar with an NO3 donor set. The dihedral angle between the two coordination planes is 6.34(9)°. The copper(II) centers are separated by 3.492(2) Å and weakly antiferromagnetically coupled (-2J = 163.6 cm-1 ), which follows from temperature-dependent magnetic susceptibility measurements in the temperature range 4.6 to 310 K. The Cu-O-Cu angle is 133.5(1)° in the super-exchange pathway. The weak antiferromagnetic coupling of the complex is interpreted in terms of countercomplementary effects of the different bridging ligands which participate in the super-exchange interaction. The magnetic moment at 310 K is ca. 2.7 B. M., but 0.2 B. M. at 4.6 K. The magnetic susceptibility is at a maximum near 140 K and decreases rapidly as the temperature is lowered to liquid helium temperature.

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Crystal Structure and Magnetic Properties of a Linear Trinuclear Ni(II) Complex

Zeitschrift für Naturforschung B ◽

10.1515/znb-2001-0107 ◽

2001 ◽

Vol 56 (1) ◽

pp. 43-48 ◽

Cited By ~ 6

Author(s):

E. Kavlakoglu ◽

A. Eimali ◽

Y. Elerman ◽

R. Werner ◽

I. Svoboda ◽

...

Keyword(s):

Crystal Structure ◽

Exchange Interactions ◽

Trinuclear Complex ◽

Antiferromagnetic Coupling ◽

Temperature Dependent ◽

Nickel Ion ◽

Phenolic Oxygen ◽

Characteristic Maximum ◽

L 13 ◽

Oxygen Atoms

Abstract Linear Trinuclear Nickel(II) Complex, Super-Exchange Interactions, Antiferromagnetic Coupling [Ni3(C2H32(CH3O)2L2] [L = 13-bis(5-chlorosalicylideneamino)propan-2-ol dianion, (C2H3O2)- = acetate, (CH3OH) = methanol] was synthesized and its crystal structure was determined. It crystallizes in the monoclinic spaceeroup P21 /n with a = 12.694(2), b = 13.281 (4), c = 15.420(3) Å, β = 111.25(2)°, V = 2422.9(9) Å3 ,Z = 2 . The molecule is a "linear" trinuclear complex with nearly octahedral coordination of each nickel ion. Adjacent nickel(II) ions are bridged by the phenolic oxygen atoms of the ligands and the oxygen atoms of the acetato ligands. The coordination sphere of the terminal nickel(II) ions is completed by the oxygen atom of the methanol. Adjacent nickel(II) centers are separated by 3.043(1) Å and weakly antiferromagnetically coupled (J1 = -3 .4 cm-1). The terminal nickel(II) centers are separated by 6.086(1) Å and very weakly antiferromagnetically coupled (J2 = -0 .3 cm-1) which follows from temperature-dependent magnetic susceptibility measurements in the temperature range 4.5 to 318 K. The magnetic moment rises from 2.99 μB at 4.5 K to 5.42 μB at 318 K. In the X(T) curve no characteristic maximum was observed.

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Emergence of size induced metallic state in the ferromagnetic insulating Pr0.8Sr0.2MnO3 manganite: Breaking of surface polarons

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v8i2.1517 ◽

2015 ◽

Vol 8 (2) ◽

pp. 2084-2093 ◽

Cited By ~ 2

Author(s):

PROLOY TARAN DAS ◽

Arun Kumar Nigam ◽

Tapan Kumar Nath

Keyword(s):

Transport Properties ◽

Metallic State ◽

Temperature Dependent ◽

Metal Insulator Transition ◽

Metal Insulator ◽

System A ◽

Surface Disorder ◽

Bulk System ◽

Magnetic Transport ◽

Grain Surface

Nano-dimensional effects on electronic-, magneto-transport properties of granular ferromagnetic insulating (FMI) Pr0.8Sr0.2MnO3 (PSMO) manganite (down to 40 nm) have been investigated in details. From the electronic and magnetic transport properties, a metallic state has been observed in grain size modulation by suppressing the ferromagnetic insulating state of PSMO bulk system. A distinct metal-insulator transition (MIT) temperature around 150 K has been observed in all nanometric samples. The observed insulator to metallic transition with size reduction can be explained with surface polaron breaking model, originates due to enhanced grain surface disorder. This proposed phenomenological polaronic model plays a significant role to understand the polaronic destabilization process on the grain surface regime of these phase separated nano-mangnatie systems. Temperature dependent resistivity and magnetoresistance data in presence of external magnetic fields are investigated in details with various compatible models.

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Crystal structure and temperature-dependent properties of Na2H4Ga2GeO8 – a novel gallogermanate

Zeitschrift für Naturforschung B ◽

10.1515/znb-2020-0159 ◽

2020 ◽

Vol 75 (9-10) ◽

pp. 805-813

Author(s):

Irma Peschke ◽

Lars Robben ◽

Christof Köhler ◽

Thomas Frauenheim ◽

Josef-Christian Buhl ◽

...

Keyword(s):

Crystal Structure ◽

Decomposition Temperature ◽

Spectroscopic Techniques ◽

Charge Balance ◽

Temperature Dependent ◽

Raman Spectroscopic ◽

Debye Temperatures ◽

Diffraction Lattice ◽

Temperature Dependent Properties ◽

Balance Structure

AbstractSynthesis, crystal structure and temperature-dependent behavior of Na2H4Ga2GeO8 are reported. This novel gallogermanate crystallizes in space group I41/acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO4 (M = Ga, Ge) tetrahedra in four-ring chains, which are connected by two different (left- and right-handed) helical chains of NaO6 octahedra. Protons coordinating the oxygen atoms of the GaO4 tetrahedra not linked to germanium atoms ensure the charge balance. Structure solution and refinement are based on single crystal X-ray diffraction measurements. Proton positions are estimated using a combined approach of DFT calculations and NMR, FTIR and Raman spectroscopic techniques. The thermal expansion was examined in the range between T = 20(2) K and the compound’s decomposition temperature at 568(5) K, in which no phase transition could be observed, and Debye temperatures of 266(11) and 1566(65) K were determined for the volume expansion.

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