Abstract: A data set of room temperature magnetic parameters for several iron oxides and sulphides was compiled from the available literature. The aim was to propose the most effective methods for assessing mineralogy, concentration and domain state within environmental magnetic studies. Establishing the magnetic mineralogy is essential for a correct interpretation of concentration and grain-size indicative parameters. Hematite and in particular goethite are recognised by their high (remanent) coercivities. The ratio of saturation remanent magnetisation to susceptibility is suited for assessing mineralogy; for low coercivity minerals, high values of the ratio are indicative of pyrrhotite. Greigite and maghemite both have intermediate ratios, while very low values suggest the presence of (titano)magnetite. From the concentration-dependent parameters mass specific susceptibility, saturation remanent magnetisation and susceptibility of anhysteretic remanent magnetisation, susceptibility displayed the least grain-size dependence. Therefore, it is perhaps the best indicator of concentration, under the proviso of uniform mineralogy and when paramagnetic and diamagnetic contributions are taken into consideration. All minerals showed a decrease in coercivity and remanence ratios with increasing grain size for sizes larger than one micrometer. In contrast, the coercivity of goethite showed an increase with grain size. Assessment of domain state was complicated by very small and large grains displaying similar magnetic properties.

Abstract: Ferromagnetism with T c > 350 K is observed in the diluted magnetic semiconductor Ni 2 + :ZnO synthesized from solution. Whereas colloidal Ni 2 + :ZnO nanocrystals are paramagnetic, their aggregation gives rise to robust ferromagnetism. The appearance of ferromagnetism is attributed to the increase in domain volumes and the generation of lattice defects upon aggregation. The unusual temperature dependence of the magnetization coercivity is discussed in terms of a temperature-dependent exchange interaction involving paramagnetic Ni 2 + ions.

Abstract: The f-electronic structures of the ground states of anionic bis(phthalocyaninato)lanthanides, [Pc2Ln]- (Pc = dianion of phthalocyanine, Ln = Tb3+, Dy3+, Ho3+, Er3+, Tm3+, or Yb3+), are determined. Magnetic susceptibilities of the powder samples of [Pc2Ln]TBA (TBA = tetra-n-butylammonium cation) in the range 1.8−300 K showed characteristic temperature dependences which resulted from splittings of the ground-state multiplets. NMR signals for the two kinds of protons on the Pc rings at room temperature were shifted to lower frequency with respect to the diamagnetic Y complex in Ln = Tb, Dy, and Ho cases, and to higher frequency in Er, Tm, and Yb cases. The ratios of the paramagnetic shifts of the two positions were near constant in the six cases. This indicates that the shifts are predominantly caused by the magnetic dipolar term, which is determined by the anisotropy of the magnetic susceptibility of the lanthanide ion. Using a multidimensional nonlinear minimization algorithm, we determined a set of ligand...

Abstract: Manganese is an element with outstanding structural and magnetic properties. While most metallic elements adopt a simple crystal structure and order magnetically---if at all---in a simple ferromagnetic or antiferromagnetic configuration, the stable phase of manganese at ambient conditions, paramagnetic $\ensuremath{\alpha}\ensuremath{-}\mathrm{Mn},$ adopts a complex crystal structure with 58 atoms in the cubic cell. At a N\'eel temperature of ${T}_{N}=95\mathrm{K},$ a transition to a complex noncollinear antiferromagnetic phase takes place. The magnetic phase transition is coupled to a tetragonal distortion of the crystalline structure. In this paper we present an ab initio spin-density functional study of the structural and magnetic properties of $\ensuremath{\alpha}\ensuremath{-}\mathrm{Mn}.$ It is shown that the strange properties of Mn arise from conflicting tendencies to simultaneously maximize according to Hund's rule the magnetic spin moment and the bond strength, as expected for a half-filled d band. Short interatomic distances produced by strong bonding tend to quench magnetism. The crystal structure of $\ensuremath{\alpha}\ensuremath{-}\mathrm{Mn}$ is essentially a consequence of these conflicting tendencies---it may be considered as a topologically close-packed intermetallic compound formed by strongly magnetic (MnI, MnII) and weakly magnetic (MnIII) or even nearly nonmagnetic (MnIV) atoms. The noncollinear magnetic structure is due to the fact that the MnIV atoms arranged on triangular faces of the coordination polyhedra are not entirely nonmagnetic---their frustrated antiferromagnetic coupling leads to the formation of a local spin structure reminiscent of the N\'eel structure of a frustrated triangular antiferromagnet. Consequently, also the other magnetic moments are rotated out of their collinear orientation. The calculated crystalline and magnetic structures are in good agreement with experiment. However, it is suggested that the magnetism leads to a splitting of the crystallographically inequivalent sites into a larger number of magnetic subgroups than deduced from the magnetic neutron diffraction data, but in accordance with NMR experiments. In a companion paper, the properties of the other polymorphs of Mn and their relative stability will be discussed.

Abstract: A massive magnetic-field-induced structural transformation in ${\mathrm{G}\mathrm{d}}_{5}{\mathrm{G}\mathrm{e}}_{4}$, which occurs below 30 K, was imaged at the atomic level by uniquely coupling high-resolution x-ray powder diffraction with magnetic fields up to 35 kOe. In addition to uncovering the nature of the magnetic field induced structural transition, our data demonstrate that the giant magnetocaloric effect, observed in low magnetic fields, arises from the amplification of a conventional magnetic entropy-driven mechanism by the difference in the entropies of two phases, borne by the concomitant structural transformation.

Abstract: 1. Review of basic magnetostatics 2. Magnetization and magnetic materials 3. Atomic origins of magnetism 4. Diamagnetism 5. Paramagnetism 6. Interactions in ferromagnetic materials 7. Ferromagnetic domains 8. Antiferromagnetism 9. Ferrimagnetism 10. Anisotropy 11. Magnetic data storage 12. Magneto-optics and magneto-optic recording 13. Magnetic semiconductors Solutions to problems.

Abstract: In this paper we have applied the full-potential linearized muffin tin orbital method and the tight-binding linearized muffin tin orbital method to investigate in detail the electronic structure and magnetism of a series of half-Heusler compounds XMZ with X = Fe,Co,Ni, M = Ti,V,Nb,Zr,Cr,Mo,Mn and Z = Sb,Sn. Our detailed analysis of the electronic structure using various indicators of chemical bonding suggests that covalent hybridization of the higher-valent transition element X with the lower-valent transition element M is the key interaction responsible for the formation of the d–d gap in these systems. However, the presence of the sp-valent element is crucial to provide stability to these systems. The influence of the relative ordering of the atoms in the unit cell on the d–d gap is also investigated. We have also studied in detail some of these systems with more than 18 valence electrons which exhibit novel magnetic properties, namely half-metallic ferro- and ferrimagnetism. We show that the d–d gap in the paramagnetic state, the relatively large X–Sb hybridization and the large exchange splitting of the M atoms are responsible for the half-metallic property of some of these systems.

Abstract: We determine the spin susceptibility in a two-dimensional electron system in GaAs/AlGaAs over a wide range of low densities from 2 X 10 9 cm - 2 to 4 X 10 1 0 cm - 2 . Our data can be fitted to an equation that describes the density dependence as well as the polarization dependence of the spin susceptibility. It can account for the anomalous g factors reported recently in GaAs electron and hole systems. The paramagnetic spin susceptibility increases with decreasing density as expected from theoretical calculations.

Abstract: We investigate the possibility of observing the anomalous Hall effect in paramagnetic two-dimensional systems. We apply the semiclassical equations of motion to carriers in the conduction and valence bands of wurtzite and zinc-blende quantum wells in the exchange field generated by magnetic impurities and we calculate the anomalous Hall conductivity based on the Berry phase corrections to the carrier velocity. We show that under certain circumstances, this conductivity approaches one-half of the conductance quantum. We consider the effect of an external magnetic field and show that for a small enough field the theory is unaltered.

Abstract: The electrochemical, photochemical and chemical control of the magnetic properties in molecular compounds is described. The preparation of various thin films of CrCr and FeFe Prussian blue on a conducting electrode allowed us to control the magnetic properties by varying the oxidation state of the component metals. The magnetic properties of CrCr Prussian blue show that the critical temperature and coercive field can be drastically modified by electrochemical treatment. That is, the compound, CrII1.29CrIII0.14[CrIII(CN)6] has ferrimagnetic properties with Tc (critical temperature) = 240 K and Hc (coercive field) = 25 G, while the reduced form, KCrII1.29CrIII0.14[CrII(CN)6], has Tc = 100 K and Hc = 220 G. Similarly, it was found that the critical temperature of FeFe Prussian blue shifts continuously from paramagnetic to magnetic with Tc = 12 K. These changes can be expressed as K4FeII4[FeII(CN)6]3 (paramagnetic) ←→ FeIII4[FeII(CN)6]3 (ferromagnetic, Tc = 4.5 K) + 4 K+ + 4e− and FeIII4[FeII(CN)6]3 (ferromag...

Abstract: The electronic structure of an isolated oxygen vacancy in SrTiO3 has been investigated with a variety of ab initio quantum mechanical approaches. In particular we compared pure density functional theory ~DFT! approaches with the Hartree-Fock method, and with hybrid methods where the exchange term is treated in a mixed way. Both local cluster models and periodic calculations with large supercells containing up to 80 atoms have been performed. Both diamagnetic ~singlet state! and paramagnetic ~triplet state! solutions have been considered. We found that the formation of an O vacancy is accompanied by the transfer of two electrons to the 3d(z 2 ) orbitals of the two Ti atoms along the Ti-Vac-Ti axis. The two electrons are spin coupled and the ground state is diamagnetic. New states associated with the defect center appear in the gap just below the conduction band edge. The formation energy computed with respect to an isolated oxygen atom in the triplet state is 9.4 eV.

Abstract: A phase control by photoirradiation is successfully achieved in a spin-Peierls system of the organic radical crystal, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which exhibits optical and magnetic bistability around room temperature with a large hysteresis loop. A nanosecond laser pulse is found to induce a transition from a diamagnetic low-temperature phase to a paramagnetic high-temperature phase both inside (296 K) and outside (11 K) the hysteresis loop. Comparison of the excitation energy dependence between transition efficiency and photoconductivity suggests that the photoinduced transition is driven by suppression of the spin-Peierls instability by the accumulation of photocarriers.

Abstract: Research in the area of molecule-based magnets is rapidly expanding, owing, in part, to numerous breakthroughs in the past decade.[1] The preparation of solid-state architectures of varying dimensionalities from specifically tailored paramagnetic building blocks has proven to be very successful, and also clearly multidisciplinary. Materials science and supramolecular chemistry efforts have joined forces with classical organic and inorganic chemistry in the design of solid-state materials whose magnetic properties rival, and sometimes even exceed, those of classic inorganic solids.[2] The moleculebased strategy allows for the preparation of unusual materials that cannot otherwise be obtained, for example, materials that combine two or more physical properties in the same compound[3] or molecules with magnetic bistability.[4] The solid-state structures of the majority of molecule-based magnetic materials consist of extended networks of paramagnetic metal ions held in close proximity by bridging ligands that allow for magnetic exchange. The dimensionality of the system dictates the overall magnetic properties and can be controlled by the use of capping ligands[5] or templating counterions.[6] Unfortunately, few ligands are capable of mediating sufficiently strong magnetic interactions between metal ions such that bulk magnetic ordering can occur. Apart from monoatomic ligands (such as oxide or halide bridges), the most effective bridging groups with respect to magnetic exchange interactions are cyanide,[7] dicyanamide,[8] and oxalate.[9] Common features of these ligands are that they contain only a small number of atoms, and that they offer a p as well as a s pathway for magnetic superexchange interactions. Organic radicals have also been successfully applied

Abstract: We show how nuclear magnetic spin-lattice relaxation dispersion of $^{1}\mathrm{H}$ water can provide a direct reliable value of the specific surface area of a cement-based material. The remarkable features of the relaxation dispersion support an interpretation in terms of coupled solid-liquid relaxation at pore interfaces, surface diffusion, and nuclear paramagnetic relaxation. The measurement is sufficiently fast to be applied continuously during the progressive hydration and setting of the material. This method is relevant to other chemically reactive porous media in chemical engineering and oil recovery.

Abstract: High-Tc copper oxides of the La2−xSrxCuO4 family show a very clear case of competition between antiferromagnetic order and superconductivity. Magnetic order can, however, coexist with superconductivity, and the experimental evidence for frozen magnetic moments in superconducting samples is reviewed here. The primary characteristics of the magnetic order are summarized and some open questions are outlined, particularly concerning the intrinsic or extrinsic nature of this order around x=0.12.

Abstract: A novel tetranuclear copper(II) complex containing alternating μ 1 , 1 -azido and monophenoxo bridges has been synthesized and characterized by spectroscopic methods, X-ray single-crystal analysis, and variable-temperaturemagnetic measurements. The magnetic behavior, investigated in the temperature range 2-300 K, indicates that the interactions between copper ions are antiferromagnetic in nature for both azido and phenoxo bridges. The temperature dependence of the magnetic susceptibility was fitted with J 1 = -12.8 cm - 1 , J 2 = -10 cm - 1 , g = 2.171, 2.1% paramagnetic component, and negligible temperature-independent paramagnetism (5 x 10 - 8 ). At variance with the earlier reports of these types of complexes containing a μ 1 , 1 -azido group, the end-on double-azido-bridged copper(II) center in this complex shows an antiferromagnetic interaction.

Abstract: High-oxygen-pressure annealing, cold pressing, and measurement of properties under pressure have been used to reveal and to follow in the single-valent perovskites $R{\mathrm{NiO}}_{3}$ $(R=\mathrm{lanthanide})$ a crossover from localized to itinerant electronic behavior. Cold pressing proved critical for obtaining nearly intrinsic transport properties such as electronic and thermal conductivity in polycrystalline samples not available as single crystals. Suppression of the thermal conductivity in the crossover compositions ${\mathrm{NdNiO}}_{3}$ and ${\mathrm{PrNiO}}_{3}$ suggests cooperative bond-length fluctuations in this region.

Abstract: Co-doped TiO2 (anatase) films prepared by spray pyrolysis at 500 °C are investigated for the possible existence of room temperature ferromagnetism (RTF). These films were characterized by x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy at room temperature, followed by studies of the temperature and magnetic field dependence of the magnetization by squid magnetometry. For Co doping of upto 10 at. %, no phase other than anatase could be detected, and there is no RTF in these films. Instead, the magnetic susceptibility χ fits the modified Curie–Weiss law χ=χ0+C/(T+θ), with θ≃5 K and magnitude of C consistent with Co2+ paramagnetism in Ti1−xCoxO2−x. Only for T⩽5 K, a hysteresis loop with coercivity Hc=200 Oe is observed. These observations suggest Co2+ paramagnetism, with exchange interaction becoming important for T⩽5 K in the case of 10% Co/TiO2 films.

Abstract: The magnetocaloric effect was investigated in LaFe11.7Si1.3, which undergoes a first-order transition at ∼188 K from the ferromagnetic to paramagnetic state. The magnetic entropy change upon a field increase from 0 to 5 T is as large as 29 J/kg K (212 mJ/cm3 K). The adiabatic temperature change obtained via direct measurements reaches 4 K under a field change from 0 to 1.4 T. The large values of entropy change and adiabatic temperature change confirmed the large potential of present compound LaFe11.7Si1.3 as a magnetic refrigerant in the corresponding temperature range.

Abstract: Some physical properties (such as lattice parameter, density and porosity) and magnetic properties of the system Mg 1-x Zn x Fe 2 O 4 ; where x=0,0.1,0.2,0.3,0.4,0.5and 0.6 have been studied. It was found that the lattice parameter increases with increasing the zinc concentration. The composition dependence of the physical properties is divided into two regions. The first one is for x ≤ 0.3 and the second one is for x > 0.3. From the magnetization measurements, the basic composition (MgFe 2 O 4 ) shows the lowest magnetization, while the composition of x=0.4 shows the highest one. The behaviour of magnetization M versus composition shows also two regions for x 0.3. The behaviour of M versus x was discussed in the bases of cation distribution. From the B-H loops, the remanence induction B r , saturation induction B s and the coercive force H s were determined and studied with x. The Curie temperature T c was determined from the measurements of the initial permeability μ i versus temperature. It was found T c decreases with increasing Zn-content. Also paramagnetic temperature T was determined from the behaviour of M s vs. T. In general it was found T p > T c by about 7-10 K.

Abstract: The diamagnetic square planar d8 complexes [meso-arylcorrolato]copper(III) become paramagnetic upon warming, indicative of the equilibrium between the [corrolato]copper(III) and the [corrolato]+• copper(II) forms of the complex. [meso-Triphenylcorrolato]copper(III) was structurally characterized and found to be saddled.

Abstract: This fluid can be used to create remarkable magnetic levitation and patterning effects. In magnetic levitation, a strong and spatially varying magnetic field exerts an upward force on a body that is sufficient to counteract its weight due to gravity. Here we show that this effect can be enhanced by immersing the body in cold oxygen gas, which provides a further strong and adjustable buoyancy force that allows a wide range of materials to be levitated in an open, unpressurized vessel. The buoyancy of magnetized liquid oxygen is sufficient to float even gold and platinum, suggesting that this technique could find application in mineral separation. An interesting periodic pattern is created on the surface of this pure elemental paramagnetic fluid.

Abstract: Suspensions of magnetic nanoparticles exhibit normal liquid behaviour coupled with superparamagnetic properties. This leads to the possibility to control the properties and the flow of these liquids with moderate magnetic fields. The magnetic control enables various experiments in fluid mechanics and gives rise to the development of numerous technical and medical applications. Ferrofluids and their general properties will be introduced and, as examples for the magnetic control of their flow and properties, thermomagnetic convection and magnetoviscous effects will be discussed in some detail.