bluuebunny/crossref_metadata_2025 huggingface dataset:
You can't have your hypothesis and test it: The importance of utilities in theories of reasoning
Authors: Poletiek Fenna H.
Published: March 2011

Mercier and Sperber's (M&S's) theory of reasoning cannot predict reasoning in the absence of an argumentative context. Applying the theory to hypothesis testing behavior, I propose that hypothesis testing is often motivated by determining the true inference and that reasoning models should account for utilities (affected by various motives, including the wish to convince) of reasoning outcomes.
True to the power of one? Cognition, argument, and reasoning
Authors: Khlentzos Drew Michael , Stevenson Bruce
Published: March 2011

While impressed by much of what Mercier & Sperber (M&S) offer through their argumentative hypothesis, we question whether the specific competencies entailed in each system are adequate. In particular, whether system 2 might not require independent reasoning capabilities. We explore the adequacy of the explanations offered for confirmation bias and the Wason selection task.
What is argument for? An adaptationist approach to argument and debate
Authors: Pietraszewski David
Published: March 2011

A consideration of selection pressures on the psychology of argument suggests that fixing the truth value of claims is not the primary criterion for argument generation or evaluation. Instead, argument psychology is designed to change representations in other minds as a way to negotiate conflicts of interest and as a way to signal social coordination.
Fiscalidad y precios en Castilla en el siglo xvii: los precios del vino en Madrid, 1606-1700
Authors: Andrés Ucendo José Ignacio
Published: March 2011

This article deals with the relations between taxation and prices levels in seventeenth century Castile through an analysis of the influence of royal and municipal taxes on the retail prices of cheap wine in Madrid between 1606 and 1700. First part describes the taxes levied on cheap wine by the Castilian Crown and the town council in Madrid. Both kinds of taxes provided the Royal and the City Treasuries with the most important part of their tax revenues. Second part analyzes how the Royal and the city authorities estimated the monetary value of the taxes and excises levied on this beverage. Lastly, third part shows that the burden of the royal and municipal taxes levied on a litre of cheap wine rose during the period. If in 1606-10 both types of taxes amounted to around 30 per cent of the retail prices of a litre of cheap wine, in the last third of the century this percentage had risen to 60-65 per cent.
KNOW ESSENTIALS: A tool for informed decisions in the absence of formal HTA systems
Authors: Mathew Joseph L.
Published: March 2011

Background: Most developing countries and resource-limited settings lack robust health technology assessment (HTA) systems. Because the development of locally relevant HTA is not immediately viable, and the extrapolation of external HTA is inappropriate, a new model for evaluating health technologies is required.

Objectives: The aim of this study was to describe the development and application of KNOW ESSENTIALS, a tool facilitating evidence-based decisions on health technologies by stakeholders in settings lacking formal HTA systems.

Methods: Current HTA methodology was examined through literature search. Additional issues relevant to resource-limited settings, but not adequately addressed in current methodology, were identified through further literature search, appraisal of contextually relevant issues, discussion with healthcare professionals familiar with the local context, and personal experience. A set of thirteen elements important for evidence-based decisions was identified, selected and combined into a tool with the mnemonic KNOW ESSENTIALS. Detailed definitions for each element, coding for the elements, and a system to evaluate a given health technology using the tool were developed.

Results and Conclusions: Developing countries and resource-limited settings face several challenges to informed decision making. Models that are relevant and applicable in high-income countries are unlikely in such settings. KNOW ESSENTIALS is an alternative that facilitates evidence-based decision making by stakeholders without formal expertise in HTA. The tool could be particularly useful, as an interim measure, in healthcare systems that are developing HTA capacity. It could also be useful anywhere when rapid evidence-based decisions on health technologies are required.
Singularities of spacelike constant mean curvature surfaces in Lorentz–Minkowski space
Authors: BRANDER DAVID
Published: March 2011

We study singularities of spacelike, constant (non-zero) mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space L3. We show how to solve the singular Björling problem for such surfaces, which is stated as follows: given a real analytic null-curve f0(x), and a real analytic null vector field v(x) parallel to the tangent field of f0, find a conformally parameterized (generalized) CMC H surface in L3 which contains this curve as a singular set and such that the partial derivatives fx and fy are given by df0/dx and v along the curve. Within the class of generalized surfaces considered, the solution is unique and we give a formula for the generalized Weierstrass data for this surface. This gives a framework for studying the singularities of non-maximal CMC surfaces in L3. We use this to find the Björling data – and holomorphic potentials – which characterize cuspidal edge, swallowtail and cuspidal cross cap singularities.
The 1903 Skinner Mission: Images of Ethiopia in the Progressive Era
Authors: McVety Amanda Kay
Published: March 2011

This essay examines the 1903 U.S. diplomatic mission to Ethiopia, which offers an unusual perspective on racial attitudes in the Progressive Era. Desirous of exploring new trade possibilities, the Theodore Roosevelt administration sent Robert P. Skinner to Addis Ababa to sign a reciprocity treaty with Emperor Menelik II. The timing of the mission had much to do with Roosevelt's global interests, but it happened to occur at a critical point for Ethiopia, which had recently thwarted an attempted Italian invasion. This victory delighted African Americans, especially those with a pan-Africanist perspective. Black Americans had long identified with the idea of Ethiopia, but they now identified with the actual nation and its leader. Black writers argued that the Ethiopians had triumphed over modern racism when they triumphed over the Italians. Those involved in Skinner's trip had a different view of the racial implications of Ethiopia's success. To them, the victory was that of a Semitic people whose triumphs were less startling. When talking about Ethiopia, black and white American observers revealed more about their own preconceptions and hopes than about the country to which the United States was making overtures.
The efficacy of psychotherapy in reducing post-psychotic trauma
Authors: Jackson C. , Bernard M. , Birchwood M.
Published: March 2011

There is now growing evidence to suggest that the experience of psychosis may be so traumatic for some that it can lead to Post Traumatic Stress Disorder (PTSD)-type symptoms or post-psychotic trauma symptoms (PPTS). There is, however, less knowledge about what psychological interventions may be helpful in reducing these symptoms. Evidence from the literature, to date, suggests that of the seven studies that have addressed this issue only four were randomized controlled trials (RCTs). However, all these studies included less than 100 patients with the vast majority reporting positive results. Overall, it seems that although cognitive-behavioural treatment (CBT)-based psychological interventions appear to be efficacious in the treatment of PPTS, the studies are too small to draw any firm conclusions and should be subjected to larger good-quality RCTs. Further research will also need to establish the role of mediating variables such as shame and depression in the treatment of PPTS.
Effects of mental health on quality of life in children and adolescents living in residential and foster care: a cross-sectional study
Authors: Damnjanovic M. , Lakic A. , Stevanovic D. , Jovanovic A.
Published: March 2011

Aims.

This study was conducted in order to evaluate the effects of mental health and quality of life (QOL) in children and adolescents living in residential and foster care.

Methods.

Two hundred and sixteen children and adolescents, aged 8–18 years, from residential and foster care participated. QOL was assessed using the Pediatric Quality-of-Life Inventory (PedsQL), levels of anxiety and depressive symptoms using the screen for child anxiety-related emotional disorders (SCARED) questionnaire and the short mood and feeling questionnaire (SMFQ), and general mental health through use of the strengths and difficulties questionnaire (SDQ).

Results.

The children and adolescents from residential care had significantly low QOL and more frequently had mental health problems. A stepwise linear regression was performed to test the associations between the SCARED, SMFQ and SDQ scores, and PedsQL (QOL). Anxiety, depressive symptoms and general mental difficulties account for significant variations in QOL (p < 0.001).

Conclusions.

Mental health problems have significant negative effects on the QOL of children and adolescents living in residential and foster care.
Affective Context of Sadness and Physiological Response Patterns
Authors: Davydov Dmitry M. , Zech Emmanuelle , Luminet Olivier
Published: March 2011

This study was conducted to test the hypothesis that two films that induce a sad feeling would elicit different physiological responses depending on an additional context of the film contents related to either avoidance (disgust) or attachment (tenderness). Reactivity was evaluated for facial behavior, heart rate, pulse transit time, skin conductance, and subjective experience. Participants reported feeling less happy and showed increased facial activity related to the sad content of both films. The sad film related to avoidance induced an increase in skin conductance level and response rate. In contrast, the sad film related to attachment induced a decrease in amplitude of skin conductance responses and heart rate. The study showed that while the common sad content of both films disturbed mood or provoked negative feelings, additional affective contexts induced either a decrease or an increase in physiological arousal.
Improving temperature estimates derived from Mg/Ca of planktonic foraminifera using X‐ray computed tomography–based dissolution index, XDX
Authors: Johnstone Heather J. H. , Yu Jimin , Elderfield Henry , Schulz Michael
Published: March 2011

Temperatures derived from Mg/Ca ratios of the calcite tests of planktonic foraminifera are distorted when samples are partially dissolved, and methods are required to quantify this source of inaccuracy. Here we compare a dissolution index (XDX), based on X‐ray computed tomography scans, to Mg/Ca of four species of foraminifera (G. ruber (white), G. sacculifer (without sac), N. dutertrei, and P. obliquiloculata) from core top sediments from the tropical Pacific, Atlantic, and western Indian Ocean. Deepwater calcite saturation values (Δ[CO32−]) at the sites ranged from 55 to −23 μmol/kg. An estimate of ΔMg/Ca (reduction in Mg/Ca due to dissolution) was made for each sample. ΔMg/Ca decreased linearly from deepwater Δ[CO32−] values of between 10 (±4) and 15 (±5) μmol/kg. These values are minimum estimates of the threshold below which Mg/Ca is affected by dissolution, as they are limited by assumptions made in calculating ΔMg/Ca. Sensitivity of Mg/Ca to Δ[CO32−] was greatest for G. ruber, where Mg/Ca decreased by 0.102 (±0.036) mmol/mol per μmol/kg. Sensitivity was similar for G. sacculifer (0.047 ± 0.015 mmol/mol per μmol/kg), N. dutertrei (0.037 ± 0.010 mmol/mol per μmol/kg), and P. obliquiloculata (0.040 ± 0.008 mmol/mol per μmol/kg). Sensitivity was similar at all sites for each species, excepting an apparently greater response for N. dutertrei from the Caribbean compared to other sites. Calibrations between XDX and ΔMg/Ca provide a means to estimate dissolution bias on Mg/Ca. Poor correlation between XDX and δ18O suggests that, for the small sample size typical for analysis, variability in initial δ18O overwhelms dissolution effects.
Tumour necrosis factor‐α stimulates human neutrophils to release preformed activin A
Authors: Chen Yi , Wu Hui , Winnall Wendy R , Loveland Kate L , Makanji Yogeshwar , Phillips David J , Smith Julian A , Hedger Mark P
Published: March 2011

Activin A, a member of the transforming growth factor‐β superfamily, is a critical early mediator of acute inflammation. Activin A release coincides with the release of tumour necrosis factor‐α (TNF‐α) in models of lipopolysaccharide (LPS)‐induced inflammation. The source of circulating activin A during acute inflammation has not been identified and the potential contribution of leukocyte subsets was examined in the following study. Human leukocytes from healthy volunteers were fractionated using Ficoll gradients and cultured under serum‐free conditions. Freshly isolated human neutrophils contained 20‐fold more activin A than blood mononuclear cells as measured by enzyme‐linked immunosorbent assay (ELISA), and both dimeric and monomeric forms of activin A were detected in these cells by western blotting. Activin A was predominantly immunolocalized in the neutrophil cytoplasm. Purified neutrophils secreted activin A in culture when stimulated by TNF‐α, but were unable to respond to LPS directly. Although TNF‐α stimulated activin A release from neutrophils within 1 h, activin subunit mRNA expression did not increase until 12 h of culture, and the amount of activin A released following TNF‐α stimulation did not change between 1 and 12 h. Specific inhibition of the p38 MAP kinase signalling pathway blocked TNF‐α‐induced activin release, and the secretion of activin A was not due to TNF‐α‐induced neutrophil apoptosis. These data provide the first evidence that neutrophils are a significant source of mature, stored activin A. Stimulation of the release of neutrophil activin A by TNF‐α may contribute to the early peak in circulating activin A levels during acute inflammation.
Effect of VIP on the balance between cytokines and master regulators of activated helper T cells
Authors: Jimeno Rebeca , Leceta Javier , Martínez Carmen , Gutiérrez‐Cañas Irene , Pérez‐García Selene , Carrión Mar , Gomariz Rosa P , Juarranz Yasmina
Published: March 2011

CD4T helper cells are decisive in the struggle against pathogens and in maintaining immune homeostasis. Nevertheless, they also drive immune‐mediated disease. Recently, emerging evidence suggests that seemingly committed Th cells possess plasticity and may convert into other types of effector cells. Vasoactive Intestinal Peptide (VIP) is an immunomodulator neuropeptide, which is able to promote or inhibit individually the differentiation or function of some T‐helper subsets. We conducted ex vivo study with erythrocyte‐depleted spleen cells from healthy mice to check the balance between cytokines and master regulators of different T‐helper subsets. This neuropeptide adversely affected the differentiation and functionality phases of Th17 cells and had a negative influence on cytokines related to Th1 function, increasing Th17 cells over those of the Th1 cell subset. With respect to Th2 subsets, VIP augmented the interleukin (IL)‐4/IL‐9 mRNA ratio, and a negative correlation between IL‐4 and IL‐9 was observed in culture supernatants. VIP augmented Th2 relative to Th1 in cell subsets. VIP decreased the iTreg/Th17 balance. Regarding the induced T‐regulatory (iTreg)/Th1 balance, VIP increased the presence of immunoregulatory cytokines in relation to IFNγ. Although additional studies are needed to clarify the role of VIP on the balance between cytokines and master regulators during T‐helper differentiation, our data show that VIP reduces Th17/Th1 and Th1/Th2 ratios. However, the iTreg/Th17 ratio was differently counterbalanced, probably because of culture conditions. Finally, this is the first study showing that VIP also modulates Th2/Th9 and iTreg/Th1 ratios.
Interactions between short-term and long-term plasticity: shooting for a moving target
Authors: Pfister Jean-Pascal , Lengyel Máté
Published: March 2011

Far from being static transmission units, synapses are highly dynamical elements that change over multiple time scales depending on the history of the neural activity of both the pre- and postsynaptic neuron. Moreover, synaptic changes on different time scales interact: long-term plasticity (LTP) can modify the properties of short-term plasticity (STP) in the same synapse. Most existing theories of synaptic plasticity focus on only one of these time scales (either STP or LTP or late-LTP) and the theoretical principles underlying their interactions are thus largely unknown. Here we develop a normative model of synaptic plasticity that combines both STP and LTP and predicts specific patterns for their interactions. Recently, it has been proposed that STP arranges for the local postsynaptic membrane potential at a synapse to behave as an optimal estimator of the presynaptic membrane potential based on the incoming spikes. Here we generalize this approach by considering an optimal estimator of a non-linear function of the membrane potential and the long-term synaptic efficacy -- which itself may be subject to change on a slower time scale. We find that an increase in the long-term synaptic efficacy necessitates changes in the dynamics of STP. More precisely, for a realistic non-linear function to be estimated, our model predicts that after the induction of LTP, causing long-term synaptic efficacy to increase, a depressing synapse should become even more depressing. That is, in a protocol using trains of presynaptic stimuli, as the initial EPSP becomes stronger due to LTP, subsequent EPSPs should become weakened and this weakening should be more pronounced with LTP. This form of redistribution of synaptic efficacies agrees well with electrophysiological data on synapses connecting layer 5 pyramidal neurons.
A giant magnetoresistance ring-sensor based microsystem for magnetic bead manipulation and detection
Authors: Gooneratne Chinthaka P. , Giouroudi Ioanna , Liang Cai , Kosel Jürgen
Published: March 2011

In this paper a novel spin valve giant magnetoresistance (GMR) ring-sensor integrated with a microstructure is proposed for concentrating, trapping, and detecting superparamagnetic beads (SPBs). Taking advantage of the fact that SPBs can be manipulated by an external magnetic field, a unique arrangement of conducting microrings is utilized to manipulate the SPBs toward the GMR sensing area in order to increase the reliability of detection. The microrings are arranged and activated in such a manner so as to enable the detection of minute concentrations of SPBs in a sample. Precise manipulation is achieved by applying current sequentially to the microrings. The fabricated ring-shaped GMR element is located underneath the innermost ring and has a magnetoresistance of approximately 5.9%. By the performed experiments it was shown that SPBs could be successfully manipulated toward the GMR sensing zone.
Magnetization precession and domain-wall structure in cobalt-ruthenium-cobalt trilayers
Authors: Li Zhen , Skomski Ralph , Liou Sy-Hwang , Michalski Steven , Chipara Mircea , Kirby Roger D.
Published: March 2011

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width that varies from about 150–60 nm. This behavior is explained in terms of a micromagnetic local-anisotropy model.
Magnetism and magnetotransport studies in Ge0.9Mn0.1Te
Authors: Lim S. T. , Bi J. F. , Teo K. L. , Liew T.
Published: March 2011

We have investigated the magnetic and magnetotransport properties of Ge1-xMnxTe (x = 0.1) grown by molecular-beam epitaxy. Our results show that the sample exhibits two ferromagnetic transition temperatures at TC = 34 K and TC* = 100 K. We infer that Tc is a long-range ferromagnetic ordering in view of sufficient carriers generating uniform ferromagnetism, whereas TC* is a short-range ferromagnetic ordering due to ferromagnetic clusters. The temperature dependence of the resistivity ρ(T) curve exhibits a shallow minimum near TC. The upturn of ρ(T) toward the low temperature (T < TC) is well described by a weak-localization model, whereas in the high-temperature regime (T > TC), the phonon scattering dominates.
Fe-based nanocrystalline FeBCCu soft magnetic alloys with high magnetic flux density
Authors: Fan Xingdu , Ma Aibin , Men He , Xie Guoqiang , Shen Baolong , Makino Akihiro , Inoue Akihisa
Published: March 2011

In this study, the magnetic properties and crystalline behavior of Fe84−xB10C6Cux (x = 0–1.3) alloys prepared by annealing the melt-spun ribbon have been investigated. A Cu element was added to this system with the aim of decreasing the coercivity because the addition of Cu clusters prior to the crystallization stimulates the nucleation of α-Fe primary crystals, which greatly influences the final microstructure. It is found that in the Fe84−xB10C6Cux alloy system, the coercivity decreases with increasing x and exhibits a minimum at around x = 1.0. When x = 1.0, the alloy exhibits excellent magnetic properties after the appropriate heat treatment with a high Bs of 1.78 T, low Hc of 5.1 A/m, and low core loss less than 4.3 W/kg at 1.0 T and 400 Hz that is about 55% of that of oriented Si-steel. These results indicate that the application of this alloy to power transformers will produce very large energy savings.
Partial band gaps in magnonic crystals
Authors: Costa C. H. O. , Vasconcelos M. S. , Albuquerque E. L.
Published: March 2011

In this work we investigate magnonic band gaps, in the THz frequency range, in periodic and quasiperiodic (Fibonacci sequence) magnonic crystals formed by layers of cobalt and permalloy. Our theoretical model is based on a magnetic Heisenberg Hamiltonian in the exchange regime, together with a transfer-matrix treatment within the random-phase approximation. For periodic arrangements, the bulk band structure is analogous to those found in photonic crystals, while for quasiperiodic multilayers it presents additional pass bands similar to those found in photonic crystals with defects.
Crystal structure and magnetic properties of R5Sn4 alloys, where R is Tb, Dy, Ho, and Er
Authors: Zhong X. C. , Zou M. , Zhang H. , Liu Z. W. , Zeng D. C. , Gschneidner K. A. , Pecharsky V. K.
Published: March 2011

Crystal structure and magnetic properties of R5Sn4 alloys with R = Tb, Dy, Ho, and Er have been studied. R5Sn4, R11Sn10, and R5Sn3 phases coexist in the annealed alloys and the content of 11:10 and 5:3 phases varies between 9 and 17 wt.%. The R5Sn4 major phase has Sm5Ge4-type orthorhombic structure with space group Pnma. Tb5Sn4 has a complex magnetic structure, spin re-orientation and ferrimagnetic-paramagnetic phase transitions occur at ∼54 and ∼84 K, respectively. For Dy5Sn4, Ho5Sn4, and Er5Sn4, the antiferromagnetic-paramagnetic phase transitions occur at about 22, 15, and 8 K, respectively. The magnetic entropy changes (−ΔSM) of all alloys are negative at low temperature and changes to positive at higher temperatures, which could be attributed to the change of magnetic states.
Thermal observables in coupled Cr7Ni molecular rings: Role and quantification of spin-entanglement
Authors: Florez J. M. , Vargas P. , García C.
Published: March 2011

This work examines the interplay between the thermal observables and the entanglement of molecular magnets conformed by antiferromagnetic rings of Cr7Ni. We show how in the quantification of the spin-entanglement, quantities such as the specific heat CMag and magnetocaloric observables (MCO) provide further insight into the description of the entanglement between molecular rings. Such quantities reproduce the entanglement-map behavior as a function of the external magnetic field and temperature. Studying ring entanglement in 2(Cr7Ni)L-like molecules (L being a molecular link) is essential in order to understand how to enhance MCO in such heterometallic systems. The magnetic field value at which the system passes from finite entanglement behavior to a factorizable thermal density matrix state is shifted by smooth modifications of the effective exchange couplings, and it is reflected onto CMag and MCO by shiftable, sharp decrements of such quantities.
FePt films 2 nanometers thick with (001) preferential orientation on a MgO underlayer
Authors: Tanaka Makoto , Ogata Yuji , Nakagawa Shigeki
Published: March 2011

A MgO underlayer with (100) preferential orientation formed on a thin Fe seed layer is used to attain L10 ordered phase 2 nm-thick FePt films with (001) orientation. The Fe[1 nm]/Pt[1 nm] bilayer can be grown epitaxially on the MgO underlayer with (100) aligned texture and the bilayer transformed into (001)-textured L10-FePt films after annealing at 600 °C. FePt films 2 nm thick with (001) preferential orientations can be prepared on a thick MgO underlayer with (100) orientation. Since the thinness of Fe and Pt layers enhances an inter-diffusion process between the layers, the crystallization and ordering temperature of FePt decreases from 550 °C to 500 °C.
Direct current voltage generated in metallic layers by spin pumping
Authors: Vilela-Leão L. H. , da Silva G. L. , Salvador C. , Rezende S. M. , Azevedo A.
Published: March 2011

We report an investigation of the dc voltage generated in a normal-metal (NM) layer by spin pumping from an adjacent ferromagnetic (FM) layer under ferromagnetic resonance (FMR) excitation. The spin-current injected across the FM/NM interface by the spin pumping effect generates a charge current along the NM layer by means of the inverse spin Hall effect. Room temperature field scan measurements were made in a series of Ni81Fe19/Pt bilayers with several thicknesses of the FM and Pt layers. By varying the angle of the in-plane magnetization we are able to accurately separate the contributions arising from anisotropic magnetoresistance and from the spin-current pumped into the NM layer by the precessing magnetization of the FM layer. The data for the spin pumping dc voltage is in excellent agreement with a theory incorporating the full dependence on the thicknesses of the FM and NM layers.
Sub-100 μm scale on-chip inductors with CoZrTa for GHz applications
Authors: Xu Wei , Wu Hao , Gardner Donald S. , Sinha Saurabh , Dastagir Tawab , Bakkaloglu Bertan , Cao Yu , Yu Hongbin
Published: March 2011

On-chip inductors with magnetic material are fabricated with complementary metal-oxide semiconductor processes. The inductors use copper metallization and amorphous CoZrTa thinfilms. Enhancements of 3.5X in inductance and 3X for the quality factor at frequencies as highas 3 GHz have been successfully demonstrated by using a continuous CoZrTa-ring structure in spiral inductors at the 100 μm scale. Further improvement of the frequency response of inductance up to 6 GHz was achieved by micro-patterning the magnetic film. The effect ofincreasing the film thickness on the performance of strip line inductors was measured and modeled. This work demonstrates significantly larger increases in inductance and quality factor atabove 1 GHz as compared to prior efforts, thereby making the added processing cost worthwhile.
Elastic and magnetostrictive properties of Tb6Fe1−xCoxBi2 (0 ≤ x ≤ 0.375)
Authors: Koehler Michael R. , Jia Lin , McCarthy David , McGuire Michael A. , Keppens Veerle
Published: March 2011

Elastic moduli and magnetostriction data are reported for polycrystalline Tb6Fe1−xCoxBi2 (0 ≤ x ≤ 0.375). The elastic moduli c11 and c44 have been measured as a function of temperature (5–300 K) and magnetic field (0–5 T), and reflect the ferromagnetic transition observed in these materials around 250 K. A remarkable elastic softening, which is partially suppressed upon application of a magnetic field, is observed at low temperatures and is believed to be linked to a structural transition that takes place in the Co-doped samples. The soft elastic moduli lead to large magnetostriction below 50 K, reaching a value of 700 ppm at 20 kOe for Tb6Fe0.75Co0.25Bi2.
Modeling of 1/f noise due to thermally induced magnetic switches of anti-ferromagnetic grains in magnetic tunneling readers
Authors: Wang Lei , Patwari Mohammed S. , Stokes Scott W.
Published: March 2011

Magnetic 1/f noise is one of the major noise sources in state-of-the-art magnetic tunneling read heads for hard disk drive applications. The 1/f noise can be induced by thermally activated magnetic switching of antiferromagnetic (AFM) grains in the reader stack. This noise mechanism is studied here by micro-magnetic modeling. The modeling shows that the 1/f like noise power spectrum can come from the addition of several Lorentzian type noise spectra corresponding to the switching of individual AFM moments that are most likely located near the edges of the AFM layer. Additionally, the modeling shows that magnetic glitches can be generated by the switching of the reference layer edge curling state at the top or bottom edge of the layer, which is induced by the switching of one or more AFM moments in those areas.
Observation of a minimum reaction initiation threshold in ball-milled Ni+Al under high-rate mechanical loading
Authors: Herbold Eric B. , Thadhani Naresh N. , Jordan Jennifer L.
Published: March 2011

Two types of microstructurally distinct ball-milled Ni+Al powder compacts are characterized for the investigation of reaction initiation threshold under high-rate mechanical loading using a modified rod-on-anvil Taylor impact-test setup. It is observed that the kinetic energy threshold for reaction decreases to a minimum then increases with milling time. It is also observed that the kinetic energy required for reaction initiation is lower for the 95% theoretical maximum density (TMD) ball-milled powder compacts than for the 65% theoretical maximum density (TMD) compacts. The results are discussed on the basis of competing effects of reactivity enhancement and deformability reduction caused by prior ball-milling of the powder mixtures.
Interactions between global and grazing bifurcations in an impacting system
Authors: Mason Joanna F. , Piiroinen Petri T.
Published: March 2011

It is well known that the locus of boundary crises in smooth systems contains gaps that give rise to periodic windows. We show that this phenomenon can also be observed in an impacting system, and that the mechanism by which these gaps are created is different. Namely, here gaps are created and disappear at points along the branches of boundary crises where they are intersected by branches of grazing bifurcations. We locate a novel type of double-crisis vertex which we call a grazing-crisis vertex. Additionally, we illustrate several types of basin-boundary metamorphosis that are intricately related with grazing bifurcations.
Magnetization reversal mechanisms in Heusler alloy spin valves
Authors: Ginley T. P. , Borchers J. A. , Kirby B. J. , Dennis C. L. , Carey M. J. , Childress J. R.
Published: March 2011

Ferromagnetic layers composed of Heusler alloys, which are predicted to be 100% spin polarized in bulk, have been incorporated into spin-valve sensors to improve performance. Transport studies of spin valves containing Co2MnGe (CMG) in the free and pinned layers show an increase in field-dependent magnetoresistance that is lower than expected. When 0.5 nm CoFe insert layers are added to the top and bottom surfaces of the 8 nm CMG free layer, the magnetoresistance increases by almost 25% relative to that measured in spin valves with CMG alone. Magnetometry data reveal that the transition between the nominal parallel and antiparallel states is sharp for samples with CoFe/CMG/CoFe, but it is sheared for samples with only CMG. To understand this difference, polarized neutron reflectivity (PNR) was used to probe the interfacial magnetic structure of spin valves with and without CoFe. Near the transition, PNR measurements for the CMG-only samples show spin-flip scattering. Fits to the data revealed that the free layer magnetization is canted relative to the field, and the orientation of the magnetization changes as the field is varied. The free layer reversal thus proceeds via coherent rotation rather than domain formation. In contrast, the absence of spin-flip scattering for the CoFe/CMG/CoFe sample in comparable fields indicates that the mechanism for the free layer reversal is domain formation. Structural analysis revealed that the interface between the free and Cu layers is less distinct in the spin valve with CMG alone relative to the CoFe/CMG/CoFe sample. Enhanced roughness may alter the coupling between the free and pinned layers and thus be responsible for both the undesirable reversal behavior and the reduced magnetoresistance.
Phase coexistence and magnetic anisotropy in polycrystalline and nanocrystalline LaMnO3+δ
Authors: Chandra S. , Figueroa A. I. , Ghosh Barnali , Phan M. H. , Srikanth H. , Raychaudhuri A. K.
Published: March 2011

We report on the phase coexistence and magnetic anisotropy in polycrystalline (bulk) and nanocrystalline (∼15 nm) LaMnO3+δ materials, which were prepared by solid state reaction and sol-gel methods, respectively. In addition to standard magnetization measurements, radio-frequency transverse susceptibility (TS) based on a very sensitive, self-resonant tunnel diode oscillator method was used to probe magnetic anisotropy and switching fields in the samples. The results revealed a coexistence of the ferromagnetic (FM) and antiferromagnetic (AFM) phases in both samples. For the bulk sample, the AFM phase significantly changed in volume fraction at ∼30 K and completely vanished around 120 K. Size reduction to the nanometer scale (∼15 nm) significantly suppressed the AFM phase while inducing surface spin disorder in the material. The large magnetic anisotropies were probed by TS experiments in both samples. Our studies showed that the magnetic properties of bulk LaMnO3+δ were strongly modified by size reduction.
Intriguing complex magnetism of Co in RECoAsO (RE=La, Nd, and Sm)
Authors: Pal Anand , Tropeano M. , Kaushik S. D. , Hussain Mushahid , Kishan Hari , Awana V. P. S.
Published: March 2011

The bulk intrinsic magnetism of Co changes dramatically when nonmagnetic La Sm and Nd in RECoAsO (RE=La, Nd, Sm). Although the itinerant ferromagnetism occurs below 80-100 K with small saturation moment, typical anti-ferromagnetic (AFM) transitions (TN1, TN2) are observed at 57 K and 45 K for Sm and at 69 K and 14 K for Nd. This is evidenced in isothermal magnetization plots as well. It is clear that Sm/Nd magnetic moments interact with the ordered Co spins in adjacent layer and thus transforms the ferromagnetic (FM) ordering to AFM.
Dielectric and viscoelastic properties of KNbO3 doped BaTiO3
Authors: Dong Liang , Stone Donald S. , Lakes Roderic S.
Published: March 2011

Fine grain (1–2 μm) 2%, 3% KNbO3-BaTiO3 ceramics have been synthesized via the solid state reaction method. Fine and coarse grain ceramics sintered at different temperatures exhibit peaks in dielectric constant and internal friction in the vicinity of transition temperatures. Doping lowered the Curie point and raised the temperatures for the structural transformations between orthorhombic and rhombohedral symmetry and broadened the response near the transformations. Dielectric and viscoelastic responses sharpened with increasing sintering cycles. This effect is attributed to a reduced core-shell effect. Doped ceramic exhibited a relaxation peak due to oxygen vacancy with a similar activation energy and relaxation time as pure material. The steep increase in dielectric constant and internal friction in the ferroelectric phase and the reduced dielectric and mechanical anomaly in the vicinity of the transformations in the fine grain ceramics are attributed to the internal stress built up at the grain boundaries. Other possible mechanisms involved such as oxygen vacancy pinning effect, constrained negative stiffness 90° domain bands and the liquid phase effect have also been discussed.
Transition from piezoelectric to deformation potential mechanism of hypersound photogeneration in n-doped GaAs semiconductors
Authors: Babilotte P. , Ruello P. , Pezeril T. , Vaudel G. , Mounier D. , Breteau J.-M. , Gusev V.
Published: March 2011

Both experiments with deeply penetrating femtosecond laser pulses and theoretical analysis demonstrate that at low laser fluences on (111) and (1−1−1−) surfaces of n-doped GaAs semiconductors the hypersound generation mechanism is the inverse piezoelectric effect. The transient electric field causing the inverse piezoelectric effect is due to the spatial separation in the built-in near-surface electric field of the electrons and holes photoexcited directly in the depletion region and also of those photoexcited outside the depletion region and diffusing toward it. However, with increasing laser fluence the amplitude of the acoustic signal generated by laser-induced transient electric fields saturates and the hypersound generation through electron–hole–phonon deformation potential mechanism becomes predominant. The peculiar dependencies of the hypersound amplitude and phase on pump laser fluence reveal the transition between the two physical mechanisms of optoacoustic conversion. The phase of the acoustic signal contains information on the temporal dynamics of the screening of the built-in electric field.
Electronic structures of Ga2O3(Gd2O3) gate dielectric on n-Ge(001) as grown and after CF4 plasma treatment: A synchrotron-radiation photoemission study
Authors: Pi T.-W. , Lee W. C. , Huang M. L. , Chu L. K. , Lin T. D. , Chiang T. H. , Wang Y. C. , Wu Y. D. , Hong M. , Kwo J.
Published: March 2011

The interfacial electronic structure of Ga2O3(Gd2O3) (GGO) on n-Ge(001) is determined using high-resolution synchrotron radiation photoemission. The excitation photon energy was specifically chosen to observe the interaction at the GGO/Ge interface (hv = 463 eV) as well as the possible diffusion of Ge up to the GGO surface (hν = 120 eV). The Ge 3d core-level spectra were fit to extract the contributing components. Photoemission measurements were done for four samples, as deposited, N2 annealed, CF4 plasma treated, and the combined CF4 plasma treated and N2 annealed. No surface passivation was employed prior to the dielectric deposition. SRPES data clearly showed that the elemental Ge in the as-deposited sample was effectively kept in the wafer. Prevention of Ge diffusion was attributed to formation of a thin germanatelike oxide layer. Other than contributions from bulk Ge, an analytical fit to the Ge 3d cores gives two components that are associated with bonding to Gd2O3 (GdGe*) and to Ga2O3 (GaGe*), which had chemical shifts of 3.46 and 1.80 eV, respectively. We hereby label them as MGe*, where M stands for either Gd2O3 or Ga2O3. Area occupations of the GdGe* and GaGe* oxides are ∼87% and ∼10%, respectively. A CF4 plasma treatment disturbs the film itself as well as the interfacial oxide so that the GGO surface begins to show both elemental Ge and Ga. Nevertheless, the follow-up N2 annealing produces the GdGe*+GaGe* layer with characteristics similar to those at the GGO/Ge interface. Both GdGe* and GaGe* states in the CN-treated sample show simultaneously a smaller chemical shift by 0.31 ± 0.02 eV than those in the as-deposited sample. The treatments also induce upward band bending on both the high κ and the Ge sides, which causes the valence band offset at the GGO/Ge interface to be 2.95 eV.
Redshift and discrete energy level separation of self-assembled quantum dots induced by strain-reducing layer
Authors: Gu Yongxian , Yang Tao , Ji Haiming , Xu Pengfei , Wang Zhanguo
Published: March 2011

We theoretically studied the role of a InGaAs and InAlAs strain-reducing layer (SRL) with different thicknesses and indium compositions covered on InAs/GaAs self-assembled quantum dots (QDs). The ground-state transition wavelength increases as the thickness and indium composition of the SRL increase. The energy separation between ground state and excited state can achieve the maximum by a proper design. The redshift is due to (1) the strain reducing in QD, (2) the potential barrier, and (3) effective mass reducing in SRL, but the latter two tend to cancel each other and the energy level separation is mainly determined by (2) and (3).
Lattice Boltzmann method for n-dimensional nonlinear hyperbolic conservation laws with the source term
Authors: Wang Zhenghua , Shi Baochang , Xiang Xiuqiao , Chai Zhenhua , Lu Jianhua
Published: March 2011

It is important for nonlinear hyperbolic conservation laws (NHCL) to own a simulation scheme with high order accuracy, simple computation, and non-oscillatory character. In this paper, a unified and novel lattice Boltzmann model is presented for solving n-dimensional NHCL with the source term. By introducing the high order source term of explicit lattice Boltzmann method (LBM) and the optimum dimensionless relaxation time varied with the specific issues, the effects of space and time resolutions on the accuracy and stability of the model are investigated for the different problems in one to three dimensions. Both the theoretical analysis and numerical simulation validate that the results by the proposed LBM have second-order accuracy in both space and time, which agree well with the analytical solutions.
Magnetic properties of Fe62Co19Ga19 films deposited on Si(100) substrates
Authors: Jen S. U. , Tsai T. L. , Li M. S. , Kuo P. C. , Lin M. Y.
Published: March 2011

Fe81–XCoXGa19 films, with x = 0−23 atom % Co, were deposited on Si(100) substrates, respectively, by the dc magnetron sputtering method. Film thickness (tf) ranged from 30 to 400 nm. We have done the following experiments on those films: saturation magnetostriction (λS), high-temperature magnetic hysteresis, x-ray diffraction (XRD), atomic force microscopy, Auger-depth profile analysis, and plane-view and/or cross-section transmission electron microscopy. Our main finding is that if x increases from 0 to 19 atom % Co, λS increases from 56 to 152 ppm, and if x continues to increase from 19 to 23 atom % Co, λS decreases. These results indicate that the addition of Co in the Fe81Ga19 alloy is advantageous in enhancing λS, if x is the correct value. From XRD, the Fe62Co19Ga19/Si(100) film comprises the A2 and B2 phases. The mechanism for large enhancement of λS in Fe62Co19Ga19/Si(100) is related to an intrinsic origin. The tf dependence of λS for the Fe62Co19Ga19 films is that: [1] in the range of 110 ≤ tf ≤ 400 nm, λS increases as tf decreases; [2] in the range of 30 ≤ tf ≤ 110 nm, λS decreases as tf continues to decrease. The λS behavior in the regions [1] and [2] is explained based on the modified Neel model. Other physical properties of the Fe62Co19Ga19 films include the following: saturation magnetization 4πMS = 1.8 – 2.0 T, coercivity HC = 35 – 64 Oe, Curie temperature TC = 597 °C, planar (mean) grain size DP = 29.6 nm, and columnar grain size DL ≈ tf.
Angular dependence of the exchange bias direction and giant magnetoresistance on different cooling-field strengths
Authors: Son Jangyup , Lee Soogil , Kim Sanghoon , Han Yoonsung , Hong Jongill
Published: March 2011

We studied the effect of different cooling-field strengths on the exchange bias by measuring the angular-dependent sheet resistance and the giant magnetoresistance of exchange-biased spin valves using a PtMn antiferromagnetic and a synthetic antiferromagnetic layer. When we annealed the spin valve at a cooling-field of 100 Oe, the exchange bias was antiparallel to the cooling-field. As we increased the cooling-field to 4000 Oe, the exchange bias direction gradually rotated and it ended up parallel to the cooling-field direction. The giant magnetoresistance also changed with the cooling-field strength. In the cooling-field range between 100 and 4000 Oe, the magnetoresistance ratios measured along the cooling-field direction were significantly reduced. However, the magnetoresistance ratios measured along the exchange bias direction increased, although still remaining smaller than those of the spin valve annealed at 100 or 4000 Oe. On the other hand, the exchange bias strength did not change significantly with the cooling-field strength.
Spin-torque-driven ferromagnetic resonance in point contacts
Authors: Staudacher T. , Tsoi M.
Published: March 2011

We demonstrate the technique of spin-torque-driven ferromagnetic resonance (ST-FMR) in point contacts, which enables FMR studies in sample volumes as small as a few cubic nanometers. In our experiments, we use point contacts ∼10 nm in size to inject both dc and microwave currents into F/N/F/AFM exchange-biased spin valves where two ferromagnetic (F) layers are separated by a nonmagnetic (N) metal spacer and one of the Fs is pinned by an adjacent antiferromagnetic (AFM) layer. High current densities produce the spin-transfer torque on magnetic moments in a small contact region and drive it to resonance at appropriate frequency of the applied microwaves. The resulting magnetodynamics are detected electrically via a small rectified dc voltage, which appears across the contact at resonance. The width of the resonance varies linearly with the applied dc bias as expected for spin transfer in spin valves. Potentially, the point-contact technique extends the applicability of ST-FMR to higher/lower frequencies, smaller sample volumes, and a broader range of materials.
Characterization of magnetic clustering and its effect on switching behavior and recording performance in perpendicular media
Authors: Jung H. S. , Ghaderi A. , Shi Zhupei
Published: March 2011

Characterization of magnetic clustering and its effect on magnetic switching behavior and recording performance are investigated. Intergranular exchange coupling constant (Jc) of full-stack media is controlled over a wide range by applying a bias voltage (VB) to the bottom oxide layer only while the other conditions remain the same. With increasing VB up to 300 V, Hn considerably increases by 25% while Hc and Hs remain constant. Magnetic correlation length (Dn) extracted from major and minor loops is plotted with Jc values estimated from the ΔH(M,ΔM) method. Two distinct regions emerge, with lower Jc and larger Dn at VB ≤ 200 V, and with higher Jc and much larger Dn at VB > 200 V. These regions are consistent with the microstructures of biased CoCrPt-SiO2 films reported elsewhere. An increase in the intrinsic switching field distribution is also observed at VB > 200 V. Good correlation between KuV/kT and Dn2, and the increase in coherent switching behavior for media with higher VB, can be understood by the magnetic clustering effect. All the recording parameters of OW, resolution, low-frequency amplitude, magnetic core width, and SNR correlate well with Dn.
Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co20Fe60B20-MgO structure
Authors: Yamanouchi M. , Koizumi R. , Ikeda S. , Sato H. , Mizunuma K. , Miura K. , Gan H. D. , Matsukura F. , Ohno H.
Published: March 2011

We investigated the dependence of perpendicular magnetic anisotropy in CoFeB-MgO on the MgO layer thickness. Magnetization curves show that a clear perpendicular magnetic easy axis is obtainable in a 1.5-nm thick CoFeB layer by depositing MgO of more than three monolayers. We investigated anisotropy in CoFeB-MgO deposited on four different buffer layers. Results show that a counter interface of CoFeB-nonmagnetic metal affects the perpendicular anisotropy of CoFeB/MgO.