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Magnetic Behavior (magnetic + behavior)

Distribution by Scientific Domains
Chemistry57%
Physics and Astronomy21%
Polymers and Materials Science17%

Selected Abstracts

Nanocrystalline Electroplated Cu,Ni: Metallic Thin Films with Enhanced Mechanical Properties and Tunable Magnetic Behavior

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010
Eva Pellicer
Abstract Nanocrystalline 3,µm thick Cu1,xNix (0.45,,,x,,,0.87) films are electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates, from a citrate- and sulphate-based bath containing sodium lauryl sulphate and saccharine as additives. The films exhibit large values of reduced Young's modulus (173,<,Er,<,192,GPa) and hardness (6.4,<,H,<,8.2,GPa), both of which can be tailored by varying the alloy composition. The outstanding mechanical properties of these metallic films can be ascribed to their nanocrystalline nature,as evidenced by X-ray diffraction, transmission electron microscopy, and atomic force microscopy,along with the occurrence of stacking faults and the concomitant formation of intragranular nanotwins during film growth. Due to their nanocrystalline character, these films also show very low surface roughness (root mean square deviation of around 2,nm). Furthermore, tunable magnetic properties, including a transition from paramagnetic to ferromagnetic behavior, are observed when the Ni percentage is increased. This combination of properties, together with the simplicity of the fabrication method, makes this system attractive for widespread technological applications, including hard metallic coatings or magnetic micro/nano-electromechanical devices. [source]

Titelbild: [An(H2O)9](CF3SO3)3 (An=U,Cm, Cf): Exploring Their Stability, Structural Chemistry, and Magnetic Behavior by Experiment and Theory (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 36 2010
36/2010)
Empfindlich und doch stabil: Einfach hergestellte und sehr gut lösliche Actinoid(III)-Salze sind als Vorstufen für eine Actinoidkomplexchemie von großem Interesse. P. Lindqvist-Reis et,al. schildern in der Zuschrift auf S.,6487,ff., wie [An(H2O)9]3+(CF3SO3)3 -Salze (An=U,Cm, Cf) direkt aus wässriger Lösung erhalten werden können , ein bemerkenswertes Ergebnis angesichts der extremen Oxidationsempfindlichkeit von UIII - und NpIII -Salzen. Sie diskutieren außerdem den Einsatz dieser Salze als Modelle für hydratisierte An3+ -Ionen in Lösung. [source]

[An(H2O)9](CF3SO3)3 (An=U,Cm, Cf): Exploring Their Stability, Structural Chemistry, and Magnetic Behavior by Experiment and Theory,

ANGEWANDTE CHEMIE, Issue 36 2010
Christos Apostolidis Dr.
Lanthanoid-artig: Röntgenbeugung und DFT-Studien ergaben, dass die Ionen [An(H2O)9]3+ der Actinoide U3+,Cf3+ in Kristallen ihrer Triflatsalze dieselbe Struktur und elektrostatische Bindung wie ihre Lanthanoid-Gegenstücke La3+,Eu3+ aufweisen. Zudem zeigte sich, dass die Neunfachkoordination in Lösung bei den leichteren Elementen weitgehend erhalten ist (siehe Bild). [source]

ChemInform Abstract: Unique Crystal Structure and Anomalous Magnetic Behavior of Quaternary U2ScB6C3.

CHEMINFORM, Issue 48 2008
V. H. Tran
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Preparation, Crystal Structure and Magnetic Behavior of New Double Perovskites Sr2B,UO6 with B,: Mn, Fe, Ni, Zn.

CHEMINFORM, Issue 4 2008
R. M. Pinacca
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Single-Crystal Structure and Magnetic Behavior of a Molecule-Based Ferrimagnet Mn[Mn0.2Cr0.8(CN)6]×4H2O.

CHEMINFORM, Issue 28 2007
Xiao-Ping Shen
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Peculiar Magnetic Behavior of the TbCu3Mn4O12 Complex Perovskite.

CHEMINFORM, Issue 50 2005
J. Sanchez-Benitez
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Crystal Structure, Magnetic Behavior and Valence State of Ytterbium in the Yb4Ni10+xGa21-x Phase.

CHEMINFORM, Issue 17 2003
L. Vasylechko
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

ChemInform Abstract: Magnetic Behavior of DyFe4Ge2 and ErFe4Ge2 Studied by 57Fe, 161Dy and 166Er Moessbauer Spectroscopy.

CHEMINFORM, Issue 32 2001
P. C. M. Gubbens
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Unusual Magnetism of an Unsymmetrical Trinickel Chain

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2008
F. Albert Cotton
Abstract An extended metal atom chain (EMAC) compound with an unsymmetrical trinickel core and the formula [Ni3(dpa)4(CH3CN)](PF6)2·2CH2Cl2 (1·2CH2Cl2, dpa is the anion of 2,2,-dipyridylamine) has the central Ni atom in an essentially square-planar configuration. Besides having four equatorial nitrogen atoms, the two terminal metal centers have axial interactions that are notably different with one having a strongly bound acetonitrile molecule with a Ni(3),N(3) distance of 2.108(5) Å while the other unit has a very weak interaction with an axial PF6 anion [Ni(1)···F(1) separation of 2.690 Å]. In these outer units, the Ni(3) atom is pulled out of the idealized plane of the four equatorial nitrogen atoms by 0.239 Å, while in the one with an axial PF6 anion the metal atom is pulled from the plane of the equatorial nitrogen atoms by only 0.097 Å. In 1 there are two unpaired electrons and an S = 1 state prevails from ca. 25 to 300 K. This magnetic behavior differs considerably from that of symmetrical trinickel EMACs with two strongly pyramidal terminal nickel atoms. A discussion of the effect of various axial ligands on the geometry of the terminal nickel atoms is provided. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis, Structure and Magnetic Properties of a Novel Linear CuII -Trimer Complex

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005
Vladimir Pashchenko
Abstract A new hexanuclear copper(II) sandwich complex based on two 10-membered macrocyclic phenylsiloxanolate ligands, {Cu6[(C6H5SiO2)5]2(OH)2(C10H8N2)2}·4(DMF)·3(H2O) (1), was synthesized and characterized by single-crystal X-ray diffraction and measurements of the magnetic susceptibility and isothermal magnetization. The cluster compound crystallizes in the triclinic system, space group P (No. 2), with a = 14.925(3) Å, b = 16.745(2) Å, c = 23.053(3) Å, , = 83.079(9)°, , = 84.836(13)°, , = 65.019(17)°, and Z = 2. The unit cell contains two identical molecules, each consisting of six interacting Cu2+ (S = 1/2) ions. Within the molecule, the six Cu2+ ions are arranged in two almost linear, parallel trimers. While pairs of oxygen atoms link the Cu2+ ions within the trimers, single oxygen atoms residing at the ends of the trimers provide the strongest intertrimer bonds. Magnetic measurements reveal an antiferromagnetic intratrimer exchange interaction, J/kB = 85 K, as the dominant magnetic coupling of the complex. By introducing a weak antiferromagnetic intertrimer coupling, J,/kB = 3.5 K, a satisfactory description of the magnetic behavior over a wide range of temperature and magnetic field is obtained. The departure of the model curves from the data at the lowest available temperature indicates the presence of additional, weak intra - and/or intermolecular interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Unusual Lattice-Magnetism Connections in MnBi Nanorods

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Kyongha Kang
Abstract Lattice parameter, particle size, and thermal expansion results obtained from high-temperature synchrotron transmission X-ray diffraction are reported for magnetostructual NiAs-type MnBi nanorods embedded in a Bi matrix. The structural data are consistent with elevated-temperature magnetic measurements that indicate a first-order nanorod Curie transition at 520,K, significantly depressed from the bulk MnBi Curie temperature of 633,K. The data suggest that the unit cell volume dependence of the magnetic behavior,also known as the volume exchange striction,of the MnBi compound is the determining factor underlying this phenomenon. The results imply that materials with magnetostructural transitions of technological interest may be altered by strain effects to tailor the interatomic distances towards the critical transition values. [source]

MnII(TCNE)3/2(I3)1/2,A 3D Network-Structured Organic-Based Magnet and Comparison to a 2D Analog

ADVANCED MATERIALS, Issue 23 2010
Kevin H. Stone
MnII(TCNE)3/2(I3)1/2 and MnII(TCNE)[C4(CN)8]1/2 [tetracyanoethylene (TCNE)] are organic-based magnets with 3D and 2D extended network structures with vastly different magnetic behavior. They have similar ferrimagnetic coupled layers of MnII(TCNE),, with different interlayer couplings, which lead, respectively, to net ferrimagnetic (Tc,=,171,K) and antiferromagnetic (Tc,=,68,K) order. [source]

Co3O4 Nanoboxes: Surfactant-Templated Fabrication and Microstructure Characterization,

ADVANCED MATERIALS, Issue 8 2006
T. He
Co3O4 nanoboxes (see figure), prepared by a template-synthesis process and composed of compactly assembled cuboid Co3O4 nanocrystals, are reported. Heterogeneous nucleation and interparticle coarsening growth of the nanocrystals is proposed as the formation mechanism. These nanoboxes are characterized by their unexpected magnetic behavior, and may lead to the possibility of novel metal oxide hierarchical structures. [source]

From Hollow to Dense Spheres: Control of Dipolar Interactions by Tailoring the Architecture in Colloidal Aggregates of Superparamagnetic Iron Oxide Nanocrystals,

ADVANCED MATERIALS, Issue 6 2004
P. Tartaj
The synthesis of spherical colloidal aggregates (see Figure) of superparamagnetic iron oxide nanocrystals with different packing fractions is reported. Using a mean-field model, the magnitude of dipolar interactions between nanomagnets has been correlated with differences in their assembly. The results could help understanding of the magnetic behavior of magnetic liposomes and hollow capsules, which are promising for drug delivery. [source]

Magneto-dielectric properties of the Y3Fe5O12 and Gd3Fe5O12 dielectric ferrite resonator antennas

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008
P. B. A. Fechine
Abstract The main objective of this work was to study the magnetic and dielectric properties of Y3Fe5O12 and Gd3Fe5O12 garnets resonator antennas obtained from a new procedure in the solid state ceramic technique. These ferrite resonator antennas (FRAs) had the ability to change their characteristics as a function of the applied magnetic field. The Y3Fe5O12 resonator was able to increase the antenna frequency range with application of external magnetic field. Some of the properties of dielectric resonator antennas (DRAs) can be actively controlled by using low-loss ferrite materials. When unbiased, these ferrite resonator antennas (FRAs) exhibit similar behavior to DRAs. However, when a DC magnetic bias is applied, the tensor nature of the ferrite permeability is invoked, and various parameters can be controlled electronically. We also studied the magnetic behavior of the antennas and did a numerical study of the gain and directivity of the ferrite resonator antennas. These results can be important to develop wideband third-generation (3G) cellular phones and other wireless products. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2852,2857, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23824 [source]

Approximation of magnetic behavior of complex nanomagnetic materials, using the "P " curves for structural characterization of magnetic suspensions

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
N. C. Popa
Abstract The "P " curves for the structural characterization of magnetic nanoparticles suspensions (complex fluids, complex powders, complex composite materials, or living biological materials having magnetic properties) are the graphical representation of the first derivative (relative to the magnetic field strength H) of the magnetization curve relative to its saturation magnetization. In the case of the above materials, the magnetic properties are conferred to various carrier liquids by artificially integrating in their structure ferromagnetic particles of different sizes. The magnetic properties are usually shown by the hysteresis curve. The structure can be seen by (electronic) micrography. The P curves offer another possibility to determine the structure of the magnetic component of a complex fluid by numerical analysis of the magnetization curve experimentally obtained. Starting from these P curves, the paper presents the possibility to approximate the magnetic behavior of these complex nanomagnetic materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Relation between Mössbauer spectroscopy and geometrical frustration factors in MCr1.9857Fe0.02O4 (M = Co, Zn)

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007
Kang Ryong Choi
Abstract In order to elucidate the role of Cr ions in MCr2O4(M = Co, Zn) exhibiting geometrically frustration and multiferroic property, we have substituted a small amount of Fe ions for Cr sites and investigated the magnetic behavior of Fe ions with Mössbauer spectroscopy. The crystal structure was found to be single-phase cubic spinel with space group of Fd3m. The lattice constants a0 and the internal structural parameter (x) of the oxygen were determined to be 8.340, 8.331 Å and 0.261 and 0.260, respectively. The Mössbauer absorption spectra at 4.2 K show that the well-developed two sextets are superposed with small difference of hyperfine fields(Hhf). The hyperfine fields of CoCr1.9857Fe0.02O4 and ZnCr1.9857Fe0.02O4 were determined to be 490 , 480 kOe and 460 , 450 kOe, respectively. Isomer shift values (,) of the two sextets are found to be 0.33 , 0.35 mm/s relative to those of Fe metal, which are consistent with the high spin Fe3+ charge state. From the results of Mössbauer measurement, it is suggested that Cr3+ ions have two different magnetic sites, and there is a correlation between hyperfine fields and degree of magnetic geometrical frustration. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electronic structure and magnetic properties of Fe3C with 3d and 4d impurities

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
I. R. Shein
Abstract We study the electronic structure, formation energies, and magnetic properties of cementite Fe3C doped by 3d and 4d transition metals (TM) by means of first-principles calculations. All TM elements demonstrate a preference for the substitution of the general iron position in Fe3C. We predict that early elements (Sc, Ti, V, Cr, Zr, and Nb) stabilize the cementite, while the end elements (Ni, Cu, Pd, and Ag) in the TM series sharply destabilize it. The magnetic properties of impurity atoms are found to depend strongly on their atomic numbers and the trends to ferromagnetic or antiferromagnetic coupling of impurities with Fe atoms in Fe3C coincide with the magnetic behavior of these impurities in Fe. The physical reason is a similar location of the Fermi level in the pseudogap of spin-down and almost filled spin-up Fed states in both Fe3C and Fe. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Magnetic impurities in small metal clusters

ANNALEN DER PHYSIK, Issue 9-10 2005
G.M. Pastor
Abstract Magnetic impurities in small metallic clusters are investigated in the framework of the Anderson model by using exact diagonalization and geometry optimization methods. The singlet-triplet spin gap ,E shows a remarkable dependence as a function of band-filling, cluster structure, and impurity position that can be interpreted in terms of the environment-specific conduction-electron spectrum. The low-energy spin excitations involve similar energies as isomerizations. Interesting correlations between cluster structure and magnetic behavior are revealed. Finite-temperature properties such as specific heat, effective impurity moment, and magnetic susceptibility are calculated exactly in the canonical ensemble. A finite-size equivalent of the Kondo effect is identified and its structural dependence is discussed. [source]

Cobalt Coordination and Clustering in ,-Co(OH)2 Revealed by Synchrotron X-ray Total Scattering

CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010
James
Abstract Structures of layered metal hydroxides are not well described by traditional crystallography. Total scattering from a synthesis-controlled subset of these materials, as described here, reveals that different cobalt coordination polyhedra cluster within each layer on short length scales, offering new insights and approaches for understanding the properties of these and related layered materials. Structures related to that of brucite [Mg(OH)2] are ubiquitous in the mineral world and offer a variety of useful functions ranging from catalysis and ion-exchange to sequestration and energy transduction, including applications in batteries. However, it has been difficult to resolve the atomic structure of these layered compounds because interlayer disorder disrupts the long-range periodicity necessary for diffraction-based structure determination. For this reason, traditional unit-cell-based descriptions have remained inaccurate. Here we apply, for the first time to such layered hydroxides, synchrotron X-ray total scattering methods,analyzing both the Bragg and diffuse components,to resolve the intralayer structure of three different ,-cobalt hydroxides, revealing the nature and distribution of metal site coordination. The different compounds with incorporated chloride ions have been prepared with kinetic control of hydrolysis to yield different ratios of octahedrally and tetrahedrally coordinated cobalt ions within the layers, as confirmed by total scattering. Real-space analyses indicate local clustering of polyhedra within the layers, manifested in the weighted average of different ordered phases with fixed fractions of tetrahedrally coordinated cobalt sites. These results, hidden from an averaged unit-cell description, reveal new structural characteristics that are essential to understanding the origin of fundamental material properties such as color, anion exchange capacity, and magnetic behavior. Our results also provide further insights into the detailed mechanisms of aqueous hydrolysis chemistry of hydrated metal salts. We emphasize the power of the methods used here for establishing structure,property correlations in functional materials with related layered structures. [source]

Homoleptic Organoderivatives of High-Valent Nickel(III)

CHEMISTRY - A EUROPEAN JOURNAL, Issue 41 2009
Pablo
Abstract Homoleptic perhalophenyl derivatives of divalent nickel complexes with the general formula [NBu4]2[NiII(C6X5)4] [X=F (1), Cl (2)] have been prepared by low-temperature treatment of the halo-complex precursor [NBu4]2[NiBr4] with the corresponding organolithium reagent LiC6X5. Compounds 1 and 2 are electrochemically related by reversible one-electron exchange processes with the corresponding organometallate(III) compounds [NBu4][NiIII(C6X5)4] [X=F (3), Cl (4)]. The potentials of the [NiIII(C6X5)4],/[NiII(C6X5)4]2, couples are +0.07 and ,0.11,V for X=F or Cl, respectively. Compounds 3 and 4 have also been prepared and isolated in good yield by chemical oxidation of 1 or 2 with bromine or the amminium salt [N(C6H4Br-4)3][SbCl6]. The [NiIII(C6X5)4], species have SP -4 structures in the salts 3 and 4, as established by single-crystal X-ray diffraction methods. The [NiII(C6F5)4]2, ion in the parent compound 1 has also been found to exhibit a rather similar SP -4 structure. According to their SP -4 geometry, the NiIII compounds (d7) behave as S=1/2 systems both at microscopic (EPR) and macroscopic levels (ac and dc magnetization measurements). The spin Hamiltonian parameters obtained from the analysis of the magnetic behavior of 3 and 4 within the framework of ligand field theory show that the unpaired electron is centered mainly on the metal atom, with >97,% estimated d contribution. Thermal decomposition of 3 and 4 proceeds with formation of the corresponding C6X5C6X5 coupling compounds. [source]

Is Cyclopropane Really the ,-Aromatic Paradigm?

CHEMISTRY - A EUROPEAN JOURNAL, Issue 38 2009
Wei Wu Prof.
Abstract Dewar proposed the ,-aromaticity concept to explain the seemingly anomalous energetic and magnetic behavior of cyclopropane in 1979. While a detailed, but indirect energetic evaluation in 1986 raised doubts,"There is no need to involve ,,-aromaticity',",other analyses, also indirect, resulted in wide-ranging estimates of the ,-aromatic stabilization energy. Moreover, the aromatic character of "in-plane", "double", and cyclically delocalized ,-electron systems now seems well established in many types of molecules. Nevertheless, the most recent analysis of the magnetic properties of cyclopropane (S. Pelloni, P. Lazzeretti, R. Zanasi, J. Phys. Chem. A2007, 111, 8163,8169) challenged the existence of an induced ,-ring current, and provided alternative explanations for the abnormal magnetic behavior. Likewise, the present study, which evaluates the ,-aromatic stabilization of cyclopropane directly for the first time, fails to find evidence for a significant energetic effect. According to ab initio valence bond (VB) computations at the VBSCF/cc-PVTZ level, the ,-aromatic stabilization energy of cyclopropane is, at most, 3.5,kcal,mol,1 relative to propane, and is close to zero when n -butane is used as reference. Trisilacyclopropane also has very little ,-aromatic stabilization, compared to Si3H8 (6.3,kcal,mol,1) and Si4H10 (4.2,kcal,mol,1). Alternative interpretations of the energetic behavior of cyclopropane (and of cyclobutane, as well as their silicon counterparts) are supported. [source]

Shape and Magnetic Properties of Single-Crystalline Hematite (,-Fe2O3) Nanocrystals

CHEMPHYSCHEM, Issue 9 2006
Huaqiang Cao Prof.
Unusual magnetic behavior of ,-Fe2O3: Rice- (a) and cube-shaped (b) single-crystalline ,-Fe2O3 nanostructures (see microstructure images) are obtained by a new hydrothermal reaction route. Different magnetic anisotropies are observed for the rice- and cube-shaped ,-Fe2O3 nanocrystals. This behavior offers possibilities for technological applications of ,-Fe2O3 with magnetic properties tailored by shape-controlled synthesis. [source]

Magnon energy gap and the magnetically structural symmetry in a three-layer ferrimagnetic superlattice

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006
Rong-ke Qiu
Abstract The magnon energy band in a ferrimagnetic superlattice with three layers in a unit cell is studied by employing retarded Green's functions and the spin-wave method. Two modulated energy gaps ,,13 and ,,23 are evaluated systematically, which exist in the magnon energy band along the Kx -direction perpendicular to the plane of the superlattice. It is revealed that the energy gap ,,13 has a direct relation with the symmetry among the spin quantum numbers and the interlayer exchange couplings, while the energy gap ,,23 relates to the symmetry among these spin quantum numbers only. These symmetries differ from the symmetry of crystallographic point groups. We define the magnetically structural symmetry that is dominated mainly by the magnetic parameters. The absence of the energy gap at a certain condition means that the system has a high magnetically structural symmetry. The magnetically structural symmetry of the superlattice, which is an intrinsic property, strongly affects the magnon energy band structure and thus the magnetic behaviors of the system. Furthermore, two complete bandgaps are observed to extend through the Brillouin zone (referred to as "magnonic crystal") in this superlattice system. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electron-density studies of molecular magnetic materials

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2004
Sébastien Pillet
For more than forty years, the experimental determination and analysis of electron densities have played a fundamental role in advances in the chemical bond concept. The present paper illustrates the application of this approach to the field of molecular magnetism with examples that recently appeared in the literature. Particular attention is attached to several classes of materials, purely organic free radicals, coordination compounds and organometallic complexes, which exhibit specific magnetic behaviors. It is shown to what extent the electron-density analysis can shed light on bonding aspects that are closely related to magnetic couplings. Relations between spin delocalization, spin polarization, superexchange and the characteristics of the electron density are described. The use of the topological theory of `atoms in molecules' allows the possible magnetic interaction pathways to be located and defined, especially through weak intermolecular contacts. The complementarity with polarized neutron diffraction and spin-density modeling techniques is particularly evident from the chosen examples. [source]