bluuebunny/crossref_metadata_2025 huggingface dataset:
Repressuring Improves Production in Mapiri Field
Authors: Clarke G.J.
Published: December 2007

Early production history of the U2 sand, Mapiri field, indicated that solution gas drive was the predominant producing mechanism, and by mid–1954 the reservoir pressure had dropped from the original 4,100 psi to below 3,000 psi for a production of approximately 3.25 million bbl, or 11 per cent of the oil initially in place. At this time it was predicted that the ultimate recovery by primary depletion would be only 5.9 million bbl or 19.6 per cent. Repressuring by gas injection was then initiated, and the reservoir pressure was raised to the original value of 4,100 psi by the end of 1957. It is planned to maintain the reservoir pressure at this level until depletion, at which time it is estimated that the recovery will be 32.4 per cent or 9,725,000 bbl, an increase of 3,825,000 bbl over recovery by primary depletion.

The performance to date has followed closely that predicted in 1954, and has indicated that gas has reentered solution in the oil leg, and that a sharp flood front has been formed. GOR's are consequently close to the solution ratio, and no serious channelling or gas breakthrough has occurred.

Introduction

Among the few major reservoirs in the Mapiri field, the U2 sand (Fig. 1), which lies at an average depth of 10,200 ft, was recognized at an early date as having good possibilities for a future gas injection project. This formation is a channel-type sand of Miocene-Oligocene age, in which the channel runs roughly north-south with the net sand thickness exceeding 60 feet in the center. The average thickness is 23.5 ft. Near the edges the thickness drops rapidly, being virtually unproducible in areas with less than 10 ft of net sand. The oil leg has a closure of about 600 ft and the water-oil contact is shown at an average depth of 9,450 ft below MSL.

Sand Characteristics

The sand is a fine to coarse-grained sandstone, hard, quartzitic and massive with some secondary cementation. It is heterogeneous with variations in vertical and horizontal permeability, and individual lenses vary widely in thickness. The porosity varies considerably both vertically and horizontally and the weighted average for the reservoir is approximately 12 per cent.
No effect of human chorionic gonadotropin treatment due to threatened abortion in early pregnancy for birth outcomes
Authors: Czeizel Andrew , Dudás István , Gidai János , Horváth-Puhó Erzsébet
Published: December 2007

Human chorionic gonadotropin (HCG) is used parenterally for treatment of threatened abortions and repeated spontaneous abortion in pregnant women. No controlled epidemiological studies of preterm birth and low birthweight newborns in pregnant women with HCG treatment have been published while the results of animal investigations were controversial. The data of 97 pregnant women with HCG treatment in the second and third months of pregnancy due to threatened abortion and/or previous spontaneous abortion(s) was compared with the data of other 38,054 pregnant women in the population-based large data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities. There was no difference in mean gestational age at delivery and birth weight, in addition the rate of preterm birth and low birthweight newborns. Parenteral HCG treatment in the early pregnancy due to threatened abortion did not associate with a higher risk for preterm births or low birthweight newborns. However, a higher occurrence of gestational diabetes was found in pregnant women with HCG treatment and there was a slight male excess among newborn infants (p=0.06).
Tabacco use in smokeless and smoking forms and its effect on periodontal health in India
Authors: Jacob Vimal , Vellappally Sajith , Smejkalova Jindra , Rajkumar Krishnan , Cermakova Eva , Fiala Zdenek , Somanathan Rakesh , Shriharsha Pilathadka
Published: December 2007

The aim of the present study was to establish the relationship between tobacco use and periodontal health in an adult sample in India. A cross-sectional population-based study was conducted in a province of southern India. A total of 805 subjects between the ages of 30 and 69 years were interviewed, and clinical examinations were made by three cooperating dentists. The examiners recorded oral mucosal findings, gingivitis, and the Community Periodontal Index of Treatment Needs index using a WHO-621 Trinity probe. Among the 805 participants, 72% were males and 28% were females. Among regular smokers, 98% were males and 2% were females. In the studied population, 64.6% visited the dentist only when they had some dental problems. Oral mucosal findings were present more in of the regular smokers and chewing tobacco users than in the non-consumers. The maximum findings from six sextants indicate that non-consumers exhibited higher rates of healthy periodontium and bleeding on probing but lower rates of pockets than tobacco consumers. The present analysis shows that tobacco use exerts a strong and chronic effect on periodontium and oral mucosa and reduces bleeding on probing.
Fulminant Wegener’s granulomatosis with multiorgan dysfunction
Authors: Sinkovic Andreja , Pahor Artur
Published: December 2007

Fulminant cases of Wegener’s granulomatosis (WG) with severe lung and kidney dysfunction may resemble pneumonia with sepsis and multiorgan dysfunction. Increased serum levels of antineutrophyl citoplasmic autoantibodies (c-ANCA) and proteinase 3 antibodies (PR3) confirm the correct diagnosis and are essential to start early immunosupressive treatment to improve the outcome. With the emphasis on diagnostic dilemmas, we present a 61-year old patient with fulminant WG, resembling pneumonia with sepsis and multiorgan dysfunction. After antibiotics and supportive measures increased serum levels of c-ANCA and PR3 confirmed the suspicion of WG and adequate immunosupressive treatment improved the patient’s condition. We concluded that it is important to include vasculitis in the differential diagnosis of unexplained multiorgan dysfunction, because only early adequate immunosuppressive therapy in combination with other resuscitation measures improves survival.
What Makes Professional Development Effective? Strategies That Foster Curriculum Implementation
Authors: Penuel William R. , Fishman Barry J. , Yamaguchi Ryoko , Gallagher Lawrence P.
Published: December 2007

This study uses a sample of 454 teachers engaged in an inquiry science program to examine the effects of different characteristics of professional development on teachers’ knowledge and their ability to implement the program. The authors analyzed results from a survey of teachers served by 28 professional development providers within a hierarchical linear modeling framework. Consistent with findings from earlier studies of effective professional development, this study points to the significance of teachers’ perceptions about how coherent their professional development experiences were for teacher learning and program implementation. The authors also found that the incorporation of time for teachers to plan for implementation and provision of technical support were significant for promoting program implementation in the program.
Preparing High-Quality Teachers: Views From the Classroom
Authors: Zientek Linda Reichwein
Published: December 2007

Every child has the right to a highly qualified teacher, yet as a nation we are reluctant to empirically investigate how teacher preparation programs are succeeding. Results from the present study suggested that (a) traditionally certified (TC) teachers felt better prepared than non–traditionally certified (NTC) teachers on communicating, planning, and using instructional strategies; (b) NTC teachers’ positive mentoring and prior classroom experiences in conjunction with the overall less positive mentoring experiences of TC teachers may have minimized differences; (c) novice teachers did not feel prepared on items related to multicultural curriculum or assessing student learning; and (d) prior classroom experiences, first year support, and program components were important, but instruction on teaching standards was of particular importance for NTC teachers.
Plant functional group composition and large‐scale species richness in European agricultural landscapes
Authors: Liira Jaan , Schmidt Torsten , Aavik Tsipe , Arens Paul , Augenstein Isabel , Bailey Debra , Billeter Regula , Bukáček Roman , Burel Françoise , De Blust Geert , De Cock Raphaël , Dirksen Jolanda , Edwards Peter J. , Hamerský Roman , Herzog Felix , Klotz Stefan , Kühn Ingolf , Le Coeur Didier , Miklová Pavlina , Roubalova Martina , Schweiger Oliver , Smulders Marinus J.M. , van Wingerden Walter K.R.E. , Bugter Rob , Zobel Martin
Published: December 2007

Question:Which are the plant functional groups responding most clearly to agricultural disturbances? Which are the relative roles of habitat availability, landscape configuration and agricultural land use intensity in affecting the functional composition and diversity of vascular plants in agricultural landscapes?

Location:25 agricultural landscape areas in seven European countries.

Methods:We examined the plant species richness and abundance in 4 km × 4 km landscape study sites. The plant functional group classification was derived from the BIOLFLOR database. Factorial decomposition of functional groups was applied.

Results:Natural habitat availability and low land use intensity supported the abundance and richness of perennials, sedges, pteridophytes and high nature quality indicator species. The abundance of clonal species, C and S strategists was also correlated with habitat area. An increasing density of field edges explained a decrease in richness of high nature quality species and an increase in richness of annual graminoids. Intensive agriculture enhanced the richness of annuals and low nature quality species.

Conclusions:Habitat patch availability and habitat quality are the main drivers of functional group composition and plant species richness in European agricultural landscapes. Linear elements do not compensate for the loss of habitats, as they mostly support disturbance tolerant generalist species. In order to conserve vascular plant species diversity in agricultural landscapes, the protection and enlargement of existing patches of (semi‐) natural habitats appears to be more effective than relying on the rescue effect of linear elements. This should be done in combination with appropriate agricultural management techniques to limit the effect of agrochemicals to the fields.
Plant phenology, leaf traits and leaf litterfall of contrasting life forms in the arid Patagonian Monte, Argentina
Authors: Campanella M. Victoria , Bertiller Mónica B.
Published: December 2007

Question: Do coexisting plant life forms differ in overall phenology, leaf traits and patterns of leaf litterfall?

Location: Patagonian Monte, Chubut Province, Argentina.

Methods: We assessed phenology, traits of green and senesced leaves and the pattern of leaf litterfall in 12 species of coexisting life forms (perennial grasses, deciduous shrubs, evergreen shrubs).

Results: We did not identify differences in phenology, leaf traits and patterns of leaf litterfall among life forms but these attributes contrasted among species. Independent of the life form, the maintenance of green leaves or vegetative growth during the dry season was mostly associated with leaves with high leaf mass per area (LMA) and high concentration of secondary compounds. Low LMA species produced low litterfall mass with low concentration of secondary compounds, and high N concentration. High LMA species produced the largest mass of leaf litterfall. Accordingly, species were distributed along two main dimensions of ecological variation, the dimension secondary compounds in leaves ‐ length and timing of the vegetative growth period (SC ‐ VGP) and the dimension leaf mass per area ‐ leaf litterfall mass (LMA ‐ LLM).

Conclusions: Phenology, leaf traits and leaf litterfall varied among species and overlapped among life forms. The two dimensions of ecological variation among species (SC ‐ VGP, LMA ‐ LLM) represent distinct combinations of plant traits or strategies related to resource acquisition and drought tolerance which are reflected in the patterns of leaf litterfall.
Wind dispersal of alpine plant species: A comparison with lowland species
Authors: Tackenberg Oliver , Stöcklin Jürg
Published: December 2007

Question: The prominent role of wind dispersal in alpine habitats has been recognized early but has rarely been quantified. The aim of this study is to compare wind dispersal under alpine and lowland conditions and to analyse whether differences are caused by species traits, e.g. terminal velocity of seeds (Vterm) or weather conditions.

Location and Methods: We characterized wind dispersal potential of > 1100 Central European species using measured Vterm To quantify the habitat effect on wind dispersal, we measured meteorological key‐parameters and simulated dispersal distance spectra of nine selected species under typical alpine conditions (foreland of the Scaletta‐glacier, Switzerland) and typical lowland conditions (grassland in Bad Lippspringe, Germany).

Results: Lowland species had higher Vterm compared to alpine species. However, this difference is absent when only species of species of open habitats are concerned. The meteorological measurements showed that the alpine habitat was mainly characterized by higher frequency and strength of updrafts. The simulations showed that under alpine conditions long distance dispersal occurred much more frequent.

Conclusions: More than 50 % of the alpine species have a fair chance to be dispersed by wind over long distances, while this proportion is less than 25 % for species from open habitats in the lowland. The more prominent role of wind dispersal in alpine habitats is mainly a result of differences in environmental conditions, namely more intense vertical turbulence in the alpine habitat, and does not result from prominent differences in plant traits, namely Vterm, between alpine and lowland species.
Opposite responses of vascular plant and moss communities to changes in humus form, as expressed by the Humus Index
Authors: Lalanne Arnault , Bardat Jacques , Lalanne‐Amara Fouzia , Gautrot Thierry , Ponge Jean‐François
Published: December 2007

Question:

Does the distribution of plant species found in forests correlate with variation in the Humus Index (based on a ranking of humus forms) and, if so, do the species exhibit different responses according to phyletic lineages?

Location:

Paris Basin, France, with a temperate Atlantic climate

Methods:

Mosses and vascular plants (herbs, ferns) were inventoried in two broad‐leaved forests with contrasting soil conditions, where 15 and 16 sites were investigated, respectively. Variety of stand age and prevailing soil conditions were analysed in 5 plots and 20 sub‐plots in a grid at each site. Mantel tests were used to estimate correlations between the Humus Index and plant species richness, taking into account spatial autocorrelation.

Results:

The local (plot, sub‐plot) species richness of moss communities increased with the Humus Index, i.e. when humus forms shifted from mull to moder. The reverse phenomenon was observed in vascular communities. The opposite response of these two plant groups could be explained by opposite strategies for nutrient capture which developed in the course of their evolutionary history.

Conclusions:

Although not necessarily causative, the Humus Index predict fairly well changes in species richness which occur in forest vegetation, provided that phyletic lineages and geographical position are taken into consideration.
Intraoperative magnetic resonance imaging in pituitary macroadenoma surgery: an assessment of visual outcome
Authors: Jones Jesse , Ruge John
Published: December 2007

✓Pituitary macroadenomas most frequently present with visual loss. Although transsphenoidal surgery remains the treatment of choice for patients with neurological manifestations, there have been several advances in its implementation over the last 5 years. Intraoperative magnetic resonance (MR) imaging has emerged as a novel quality control measure, with the potential to guide the surgeon to tumor remnants concealed from the operating microscope. Investigators have reported enhanced resections when using intraoperative MR imaging, leading to complete tumor removal in a larger proportion of cases. Further debulking of unresectable lesions may also prove beneficial in delaying symptom recurrence and facilitating radiotherapy, where distance between the tumor and optic chiasm is an important predictor of visual outcome. However, confirmation of such advantages is complicated by the fact that most macroadenomas are both indolent and hormonally silent, necessitating years of follow-up. Experienced pituitary surgeons will operate as safely with intraoperative MR imaging as without it, perhaps due to a balance between more elaborate resections and better visualization. Intraoperative MR imaging represents a new technique applied to an old problem in tumor surgery: complete, safe resection.
Theory of Magnetic Phase Transitions
Authors: Landau David P.
Published: December 2007

The current state of theoretical understanding of magnetic phase transitions is reviewed. General concepts, including critical exponent relations, scaling, and universality are presented. Several ‘characteristic’ models are described and results from mean‐field (Landau) theory, renormalization group, and various numerical approaches are presented for phase diagrams and exponent values.
Theory of Magnetocrystalline Anisotropy and Magnetoelasticity in Transition‐metal Systems
Authors: Wu Ruqian
Published: December 2007

Progresses of the first principles determinations of magnetocrystalline anisotropy of transition metal systems are reviewed in this chapter. It is clear that modern density functional approaches can provide reliable predictions for magnetic anisotropy energies of transition metal elements in different environments. The physical pictures extracted from theoretical data are indispensable for manipulations of magnetic anisotropy needed for technological applications. The present status of theoretical capability for studies of magnetostriction is also discussed.
Theory of Magnetocrystalline Anisotropy and Magnetoelasticity in 4
f
and 5
f
Metals
Authors: Johansson Børje , Brooks Michael S.S.
Published: December 2007

The origins and consequences of magnetocrystalline anisotropy energy (MAE) and magnetoelastic coupling in terms of the electronic structure of 4f and 5f elements are reviewed. In the heavy rare‐earth metals, the large molecular fields dominate and the MAE arises primarily from the crystalline electric field (CEF) with modifications due to the magnetostriction. In lighter rare earths, the molecular fields can be small and the MAE energy may then be dominated by multipolar interactions. The light actinide metals do not order magnetically, however, compounds of light actinide metals have a rich variety of magnetic ordering strongly influenced by the MAE energy and magnetoelastic effects, with CEF and multipolar interactions frequently being of the same order as exchange interactions.
Magnetism of Low‐dimensional Systems: Theory
Authors: Blügel Stefan , Bihlmayer Gustav
Published: December 2007

The article discusses the ground‐state properties of low‐dimensional magnets from the viewpoint of the electronic structure theory. The results presented arose from first‐principles calculations based on the material‐specific density‐functional theory. The focus lies on ultrathin films, wires, chains, and clusters with ferromagnetic, antiferromagnetic, and complex noncollinear magnetic phases. We discuss which systems become magnetic in low dimensions, their respective values for the spin and orbital magnetic moments, the magnetic ground‐state structures, and the magnetic anisotropy determining the orientation of the magnetization as well as how these properties are altered by respective substrates. The emphasis of the article lies in the development of the physical intuition by discussing the chemical trend of the properties of these magnets. Case studies of benchmark systems such as the magnetic surface alloy c(2 × 2)‐MnCu/Cu(100), Ni/Cu(100), which exhibits a magnetic reorientation transition, Fe/W(110), or Co chains on Pt(111) are discussed in more detail. A brief introduction to the basic concepts, notions, models, and theory is given, in order to provide a framework in which the surprising and partly peculiar results can be understood and interpreted. This includes the density‐functional theory, the Heisenberg model, the dipolar and magnetocrystalline anisotropy, the Dzyaloshinsky–Moriya interaction, the Stoner model, the role of the coordination number for the appearance of magnetism, and the estimation of the critical temperature.
Molecular Magnets: Phenomenology and Theory
Authors: Pederson Mark R. , Baruah Tunna
Published: December 2007

One special class of molecular magnets may be characterized as a finite array of exchange‐coupled transition metal ions that are held in place by ligands. Depending upon the relative strength of the exchange‐coupling and the spin‐orbit interactions, two different types of collective excitations can emerge as the low‐energy excitations. When spin‐orbit interactions are negligible, the lowest excitations are generally highly correlated and are associated with changes in spin‐coupling. Such systems may be described within a Heisenberg Hamiltonian. A description of how to calculate parameters for such a Hamiltonian is presented in this work. However, the phenomenon now referred to as resonant tunnelling of magnetization (RTM) occurs when the exchange coupling is sufficiently strong that the electronic ground state of the molecule may be well idealized as a single Ising‐like configuration of spin‐ordered metal centers. Within this idealization the spin‐orbit energy depends upon axis of spin‐quantization and the magnetic behavior can be described in terms of a simple anisotropy Hamiltonian. In this work we review these points through discussions of two nanostructures which here are respectively referred to as the V
15
spin molecular magnet and the Mn
12
‐Acetate anisotropic molecular magnet. The distinctions between these two classes are reviewed. In particular we emphasize that more complicated collective behaviors may occur in cases with either low‐energy electronic excitations or for cases where a decoupling of the kinetic‐exchange and spin‐orbit interaction energies does not occur. For the latter idealized case, it is still somewhat remarkable that the anisotropy Hamiltonians of many of the AMM may be computationally determined from second‐order perturbative analyses of the collinear spin‐ordered state within an all‐electron density‐functional formalism. The primary emphasis of this work is to provide many details related to the perturbative derivation of the Hamiltonian for an AMM. A combination of analytic and computational techniques are used in the derivation.
Interplay of Superconductivity and Magnetism
Authors: Takahashi Saburo , Maekawa Sadamichi
Published: December 2007

The interplay between superconductivity and ferromagnetism in superconductor/ferromagnet structures are discussed. One of the novel phenomena due to the proximity effect in the structures is a damped oscillation of the Cooper‐pair wavefunction in ferromagnets, leading to ferromagnetic Josephson π junctions. It is demonstrated that the π junctions are used as quantum bit (qubit) in quantum computing. Andreev reflection at superconductor/ferromagnet point contacts provides a powerful method for probing the spin‐polarization of various ferromagnets. Spin injection in hybrid nanostructures allows the electrical control of the interplay of superconductivity and magnetism.
Magnetization Dynamics Including Thermal Fluctuations: Basic Phenomenology, Fast Remagnetization Processes and Transitions Over High‐energy Barriers
Authors: Berkov Dmitri V.
Published: December 2007

This chapter is devoted to general problems arising as a result of numerical simulations of dynamical remagnetization properties taking into account thermal fluctuations. After a short introduction to the dissipation treatment in micromagnetics, we proceed with the detailed analysis of difficulties emerging when thermal fluctuations are included in the micromagnetic equation of motion, converting this deterministic differential equation into a stochastic one. Special attention is paid to thermal noise correlations, which can appear as a consequence of the discretization of a continuous micromagnetic problem. We conclude with a brief review of numerical methods developed for the study of the transitions over high‐energy barriers, that is, in the situation where standard Langevin dynamics fails due to prohibitively large computational times.
Classical Spin Models
Authors: Nowak Ulrich
Published: December 2007

Classical spin models bridge the gap between a full electronic description of a magnetic material and conventional micromagnetism, where magnetic properties are calculated on the basis of a continuum theory for the energy of the system under consideration. Since spin models take into account magnetic configurations on an atomic level, they make it possible to investigate ferromagnets as well as antiferromagnets or even heterostructures composed of both of them. While well‐established methods exist for the calculation of thermal equilibrium properties, the investigation of thermally activated spin dynamics is a newer field of research which is currently developing.

One goal of this review is to give an overview on numerical approaches related to classical spin systems, where the most established methods are either a numerical solution of the Landau–Lifshitz–Gilbert equation with Langevin dynamics or Monte Carlo simulations. Special emphasis is laid on the relation between these two methods and on the possibility to quantify the steps of a Monte Carlo procedure in terms of realistic time intervals. Furthermore, as typical applications of these numerical techniques, this overview includes a description of thermally activated magnetization switching in cylindrical geometries as well as an introduction to the simulation of exchange bias.
Nonlinear Magnetization Dynamics in Nanomagnets
Authors: Serpico Claudio , Bertotti Giorgio , Mayergoyz Isaak D. , d'Aquino Massimiliano
Published: December 2007

Landau–Lifshitz–Gilbert dynamics is investigated for uniformly magnetized particles subject to constant, pulsed, and circularly polarized applied fields. The Landau–Lifshitz–Gilbert equation is treated as a nonlinear dynamical system on the unit sphere. The equilibria and the phase portraits of this dynamical system, the nature of conservative (precessional) dynamics, and the nature of dissipation are discussed. Conservative Landau–Lifshitz dynamics is studied in detail and analytical expressions are derived for this dynamics in terms of elliptic functions. Then the problem of magnetization switching is studied in detail. Damping and precessional switchings of magnetization in spheroidal particles are discussed for rectangular field pulses, and expressions for critical fields and pulse durations are derived. The phenomenon of ringing, which occurs as the final stage of magnetization switching, is analytically studied using the averaging technique. The final section is devoted to the study of Landau–Lifshitz–Gilbert dynamics in uniformly magnetized particles with rotationally invariant properties, subject to a circularly polarized external field. By using geometric and topological considerations, exact uniform‐mode solutions of the full nonlinear dynamics are obtained for arbitrary values of the excitation conditions. The stability of these solutions is investigated and the conditions leading to periodic or quasiperiodic motions of the magnetization are established. Finally the problem of ferromagnetic resonance is treated using the developed analytical techniques.
Magnetic Properties of Systems of Low Dimensions
Authors: Allenspach Rolf
Published: December 2007

The topic of low‐dimensional ferromagnetism is presented by means of examples: three specific systems illustrate phase transitions, domain patterns, and domain walls. Stripe‐domain phases and their transformations are described in ultrathin, perpendicularly magnetized Fe/Cu films, and related to two‐dimensional phase transitions. The domain patterns in small elements are discussed in stepped Co/Cu(001), an in‐plane‐magnetized system with tunable anisotropy. A wealth of different domain patterns is observed, exhibiting a distinct size and thickness dependence. A microscopic investigation of domain walls that are confined to small elements and pinned at constrictions is performed in Fe
20
Ni
80
. The wall types and profiles are found to deviate strongly from those encountered in extended films. A comparison with micromagnetic simulations leads to insight into the energetics driving these modifications.
Domain Wall Propagation in Magnetic Wires
Authors: Ono Teruo
Published: December 2007

Experimental aspects of the domain wall (DW) propagation in magnetic nanowires are reviewed. In the first part, after an introduction of the detection technique of the DW propagation by using the giant magnetoresistance effect, the DW propagation by an external magnetic field including DW velocity measurements is described. In the second half, direct observation of the DW motion induced by an electrical current is presented. Magnetic force microscopy (MFM) is used to show that a single domain wall can be displaced back and forth by positive and negative pulsed‐currents.
Nonlinear Multidimensional Spin‐wave Excitations in Magnetic Films
Authors: Demokritov Sergej O. , Slavin Andrei N.
Published: December 2007

Spin‐wave excitations provide a basis for the description of spatial and temporal magnetization distributions in magnetic samples under the general assumption that the total length of the magnetization vector is locally conserved. The magnetization dynamics in this case results in the precession of the magnetization vector and is described by the well‐known Landau–Lifshitz torque equation. Linear plane waves of magnetization (or spin waves) corresponds to a spatially nonuniform solution of this equation for relatively small precession angles. For larger precession angles the intrinsic nonlinearity of the Landau–Lifshitz equation should be taken into account, and a new basis of intrinsicallynonlinearspin‐wave excitations—multidimensional quasistable nonlinear spin‐wave packets formed as a result of the nonlinear interaction between the individual plane spin waves—should be used. In magnetic films, such intrinsic nonlinear spin‐wave excitations are the one‐dimensional spin‐wave solitons and two‐dimensional spin‐wave bullets. These nonlinear excitations can be experimentally studied and visualized by means of the space‐ and time‐resolved Brillouin light‐scattering technique. This chapter gives a brief description of the theory of nonlinear spin waves in magnetic films based on the classical Hamiltonian formalism, and a short summary of the experimental methods used for the investigation of spin‐wave processes. The description of different methods of excitation of nonlinear spin‐wave modes is given, and the examples of experimental investigations of bright, dark, spatial, and temporal one‐dimensional spin‐wave solitons, and the two‐dimensional propagating spin‐wave bullets are presented. A novel type of symmetry‐breaking Möbius solitons generated in a magnetic active ring with parametric pumping, as well as the standing evanescent spin‐wave bullet generated by spin‐polarized current in thin metallic films are also discussed. The chapter gives an overview of the recent experimental achievements in the field of nonlinear spin‐wave dynamics in magnetic films and relates these achievements to the progress in the general field of nonlinear wave dynamics.
Investigation of Domains and Dynamics of Domain Walls by the Magneto‐optical
K
err‐effect
Authors: Schäfer Rudolf
Published: December 2007

Kerr microscopy allows to image magnetic domains and magnetization processes in an optical polarization microscope. The method is based on the magneto‐optical Kerr effect, that is, the rotation of plane‐polarized light in dependence of the magnetization direction on reflection from a nontransparent sample. By means of an analyzer, this rotation is converted into a (in general weak) domain contrast that can be enhanced by digital image processing. Kerr microscopy is the most versatile domain imaging method with several advantages: (i) By digital enhancement, domain contrast can be seen on virtually all kinds of ferro‐ and ferrimagnetic materials. (ii) The Kerr effect is directly sensitive to the magnetization vector whose direction can also quantitatively be measured (at least in soft magnetic materials). (iii) There is no restriction in specimen size and shape, and samples can easily be manipulated during observation. (iv) Arbitrary magnetic fields can be applied, so that nucleation and magnetization processes can be observed in real time. (v) Kerr microscopy offers the potential of high‐speed observation of dynamic processes. (vi) The magneto‐optical information depth is some 10 nm in metals. This makes it possible to separately image the domains in multilayer structures. Drawbacks are (i) a limited lateral resolution to some tenths of a micrometer and (ii) the restriction to the imaging of surface domains in bulk materials. In this article, the possibilities of Kerr microscopy for the investigation of domains and domain dynamics are reviewed together with physical and technological fundamentals.
Magnetization‐induced Second Harmonic Generation
Authors: Kirilyuk Andrei , Rasing Theo
Published: December 2007

The magnetization‐induced effects in the nonlinear optical response of magnetic media—magnetization‐induced second‐harmonic Generation (MSHG)—lead to very strong and novel nonlinear magneto‐optical (MO) phenomena that appear to be very sensitive to magnetic interface properties. This surface/interface sensitivity of MSHG in combination with the very large MO effects has led to a fast development of this technique over the past decade. On the one hand, an extreme sensitivity of MSHG to the electronic and magnetic structure of clean surfaces has been successfully demonstrated. On the other hand, the penetration depth of light allows one to use this sensitivity to study buried interfaces in multilayer systems. Further experimental developments of the MSHG technique, like space‐ and time resolution as well as magnetization sensitive sum frequency generation, appear to be promising as well.
Investigation of Spin Waves and Spin Dynamics by Optical Techniques
Authors: Hillebrands Burkard , Hamrle Jaroslav
Published: December 2007

This review describes the current state of the art of optical techniques used to study the magnetization dynamics in ferromagnetic materials. Most optical techniques provide a spatial resolution defined by the wavelength limit of the used light. The techniques can be roughly divided into the two classes (a) frequency‐scale techniques such as Brillouin light scattering and Kerr effect ferromagnetic resonance and (b) timescale techniques such as time‐resolved, stroboscopic Kerr effect magnetometry. These techniques are presented and illustrated with selected experiments.
High‐energy Surface Spin Waves Studied by Spin‐polarized Electron Energy Loss Spectroscopy
Authors: Etzkorn Markus , Anil Kumar Parameswaran Sarala , Kirschner Jürgen
Published: December 2007

In this chapter, studies of high wave‐vector spin waves at surfaces are discussed. At present, the only technique that allows experimental access to this type of spin waves is spin‐polarized electron energy loss spectroscopy (SPEELS). In this experiment, a beam of spin‐polarized, monochromatic electrons is scattered from a magnetic sample. The scattered electrons are analyzed with respect to their wave vector and energy transfer to the sample. The excitation of spin waves results in specific loss features in the SPEEL spectra, as is shown on the example of three different systems, fcc Co on Cu(001), hcp Co on W(110), and tetragonal distorted thin Fe films on Co/Cu(001). In all three systems, the spin waves show a pronounced dispersion, that is, a dependence of the spin‐wave energy on the wave vector, which allows conclusions about the exchange interaction at the topmost surface layers. The spin‐wave loss features in the spectra also show a large intrinsic width that results from the strong damping of these excitations by the decay into electron–hole pairs. In this chapter, the results obtained by SPEELS are also compared to data measured by complementary experimental techniques and recent theoretical calculations.
Chemical Synthesis of Monodisperse Magnetic Nanoparticles
Authors: Wang Chao , Sun Shouheng
Published: December 2007

This chapter reviews briefly the recent advance in chemical synthesis of monodisperse magnetic nanoparticles. It covers mainly the syntheses of metallic Co, Fe, ferrite MFe
2
O
4
(M = Fe, Co, Mn), alloy FePt, CoFe, core/shell structured FePt/Fe
3
O
4
, and dumbbell‐like Au–Fe
3
O
4
nanoparticles. The unique magnetic properties observed from these nanoparticles are also described. Shape‐controlled synthesis and assembly of iron oxide and FePt nanoparticles are outlined as two examples to demonstrate that shape can be used to induce texture in a self‐assembled superlattice array.
Nanoimprint Technology for Patterned Magnetic Nanostructures
Authors: Chou Stephen Y.
Published: December 2007

This chapter describes the principle of nanoimprint lithography, different nanoimprint forms and their relative merits and shortcomings, key factors in nanoimprinting (masks, materials, pressing methods and imprinting pressure uniformity, material dispensing methods, vacuum, mold separation), examples of nanoimprinting in magnetic nanostructure fabrication, control of magnetic structure properties by patterning, the principle of quantized magnetic disks (QMDs) (patterned magnetic media), and the fabrication and commercial future of QMDs. The invention and development of QMDs and nanoimprint are intertwined, and this history is briefly discussed. The chapter is primarily based on author's own research in the field in the last 16 years.
Ultrafast Magnetodynamics with Lateral Resolution: A View by Photoemission Microscopy
Authors: Dürr Hermann A. , Schneider Claus M.
Published: December 2007

The rapidly increasing information density required of modern magnetic data storage devices raises the question of the fundamental limits in bit size and writing speed. Magnetic‐field‐induced magnetization reversal down to picosecond timescales depends on magnetic pulse shape and strength as well as on the sample magnetic properties and dimensions. Optical control of magnetization dynamics is possible on a subpicosecond timescale. This chapter gives an overview of how the combination of magnetic microscopy with lateral resolution down to ∼10 nm and synchrotron/laser light sources with pulses ranging form 50–0.1 ps can address the relevant dynamical processes in magnetic materials.
Soft Magnetic Bulk Glassy and Bulk Nanocrystalline Alloys
Authors: Inoue Akihisa , Makino Akihiro , Bitoh Teruo
Published: December 2007

Soft magnetic bulk glassy alloys have been synthesized in a variety of alloy systems by the copper mold casting process for 10 years since 1995. Their typical alloy systems are classified into five groups, that is (i) Fe(Al, Ga)metalloid, Fe(Cr, Mo)Gametalloid, and FeGametalloid, (ii) (Fe, Co)(Zr, Hf, Nb, Ta)B, (iii) (Fe, C)LnB, (iv) Fe(Cr, Mo, W)CB, and (v) (Fe, Co)BSi(Zr, Nb). The Fe‐ and Co‐based soft magnetic glassy alloys exhibit a large supercooled liquid region beyond 50 K before crystallization. The bulk glassy alloys have been produced in a thickness range of up to 6 mm by the copper mold casting method. In addition, the application of the consolidation technique using the viscous flow phenomenon of the Fe(Al, Ga)metalloid alloys caused the formation of fully dense bulk glassy alloys (BGAs) with rather good soft magnetic properties. The combination of good soft magnetic properties, high glass‐forming ability (GFA), and good workability into a bulk form holds promise for future development as a new type of soft magnetic material.
Rare‐earth Transition‐metal Magnets
Authors: Rodewald Werner
Published: December 2007

Most of the SmCo or NdFeB magnets are produced by powder metallurgy in a large variety of shapes. The basic production processes and their impact on the magnetic properties are reported. Alternative production routes and the achieved magnetic properties are reviewed.

The magnetization of rare‐earth transition‐metal (RE–TM) magnets and the different coercivity mechanisms are presented in order to assist in proper application.

Commercial NdFeB magnets can be operated at temperatures up to 230 °C. Owing to the higher Curie temperatures, sintered SmCo5magnets can be applied up to 250 °C, standard Sm2(Co,Cu,Fe,Zr)17magnets up to 350 °C, and newly developed Sm2(Co,Cu,Fe,Zr)17magnets even up to 550 °C. The basic features, which determine the temperature stability of RE–TM magnets, are discussed in detail.

Sometimes, RE–TM magnets need to be operated in hot and humid climates. The RE‐rich constituents of sintered NdFeB magnets are sensitive to corrosion by oxidation and hydrogen embrittlement, which may result in a disintegration of surface layers. The corrosion stability of advanced NdFeB magnets could be improved significantly by replacing corrosion‐sensitive constituents by more noble compounds. In aggressive climates, however, NdFeB magnets need protection by proper coatings. In contrast, SmCo5or Sm2(Co,Cu,Fe,Zr)17magnets hardly suffer any corrosion in hot and humid climates.

In applications, sintered magnets may experience mechanical stress. Some mechanical properties of sintered NdFeB magnets, for instance, the compression and the bending strength, the fracture toughness, the Young's modulus, and the Vickers hardness are reviewed, depending on the average grain size.
Superparamagnetic Particles
Authors: Mørup Steen , Hansen Mikkel Fougt
Published: December 2007

The magnetic properties of nanoparticles are reviewed with special emphasis on magnetic relaxation phenomena. After an introduction to superparamagnetic relaxation phenomena, we give a brief introduction to synthesis of nanoparticles and how they can be characterized by standard techniques such as X‐ray diffraction, electron microscopy, and other techniques. We then describe how one can study magnetic relaxation phenomena in noninteracting nanoparticles by different experimental techniques such as DC and AC magnetization measurements, Mössbauer spectroscopy, and neutron scattering. Subsequently, the influence of interparticle interactions on the relaxation is discussed, and it is shown that both magnetic dipole and exchange interactions between nanoparticles can have a significant influence on the relaxation phenomena. Finally, we discuss the magnetic structure in nanoparticles and how spin canting and transverse relaxation can influence the magnetic properties of nanoparticles.
Current Status and Future Development of the Magnetic Materials Industry in China
Authors: Luo Yang
Published: December 2007

Recently, the economy in developed countries has got rid of the shadow of recession that took place during the last decade: economic recession in Japan began in the early 1990s, whereas in Europe the recession has not been as strong as expected, and the US economy has been weakened somewhat since the end of 2000. The only exception is China, where the economic boom has continued from the middle of the 1980s with a GDP growth of around 9% per year. These economic developments have had a strong impact on the structure of magnet industries in the world. Owing to the rising cost of manufacturing and a drop in the price of sales, the production of magnets in developed countries has become extremely difficult. As a consequence, western magnet manufacturers produce magnetic assemblies with higher added values, while their magnet production has been partially shifted to developing countries, including China. Product quality in China has been steadily improving during the last decade. From this point of view, Part I of this contribution deals with the macroeconomy aspects of the present and future trends.

Part II of this contribution deals with the current status and future trends of the hard magnet industry. Depending on their coercivity or their ability to keep magnetization over long times, magnets are divided into two groups: Soft magnetic materials lose their magnetic moment completely if the applied magnetic field is removed. Hard magnetic materials keep their magnetic moment over many years without applying a magnetic field. Three main types of hard magnetic materials are available: Alnico, hard ferrites, and rare‐earth magnets (SmCo, NdFeB, etc.). Along with the full dense sintered magnets, bonded magnets are also developed in China. Presently, the hard ferrites are the majority of commercially available magnets, but rare‐earth‐based magnets are developing rather fast, both qualitatively and quantitatively. Analyzing the situation of the global magnet industry more deeply and precisely, it turns out that since 1985 the structure of the global magnet industry has changed considerably: Western magnet manufacturers have started to produce downstream devices, such as higher‐valued assemblies, while their magnet production has been reduced or has shifted to developing countries, including China. In Part II, the current status and future trends of the hard magnet industry are reviewed on the basis of statistical data.
Half Metals
Authors: Venkatesan M.
Published: December 2007

The classification of half‐metals is discussed taking account of both itinerant and localized electrons. The recent developments in the search for new half‐metals in oxides, nitrides, sulfides, and Heusler alloys are presented. The different experimental techniques for measuring spin polarization are summarized. The difficulties in measuring the spin polarization directly forced the exploration of other experimental techniques to identify a half‐metal, apart from an integral spin moment, metallic conduction criteria, and band‐structure calculations. The effect of surface/interface states on half‐metallicity is reviewed as the challenges remain in controlling the composition, defects, atomic ordering both in the bulk and at the interface. The possible applications of half‐metals, ideal sources of spin‐polarized electrons, in spin electronics are outlined.
Magnetism and Quantum Criticality in Heavy‐Fermion Compounds: Interplay with Superconductivity
Authors: Stockert Oliver , Nicklas Michael , Thalmeier Peter , Gegenwart Philipp , Steglich Frank
Published: December 2007

The physics of heavy‐fermion compounds is reviewed with a special emphasis on systems located in the vicinity of quantum critical points (QCPs). After a brief introduction into the basic concepts of QCPs, this chapter mainly focuses on the experimental situation in some prototypal heavy‐fermion systems. The discussion of CeCu2Si2and CeTIn5 (T = Co, Ir, Rh), which can be described within aconventionalpicture of a QCP, is followed by a review of theoretical aspects of the different observed behavior at QCPs. However, several systems do not follow this conventional picture of a QCP, but exhibitunconventionalbehavior which is exemplified on one important member, YbRh2Si2. The experimental data are compared with existing theories.