bluuebunny/crossref_metadata_2025 huggingface dataset:
Frame Dominance in Infants With Hearing Loss
Authors: von Hapsburg Deborah , Davis Barbara L. , MacNeilage Peter F.
Published: March 2008

Purpose

According to the frames then content (f/c) hypothesis (P. F. MacNeilage & B. L. Davis, 1990), the internal structure of syllables with consonant plus vowel structure (CV) during canonical babbling is determined primarily by production system properties related to rhythmic mandibular oscillations (motor frames). The purpose of this study was to evaluate whether auditory sensitivity affects the internal organization of CV syllables in infants identified in the 1st year of life with hearing loss.

Method

CV co-occurrence patterns were analyzed for 13 infants with varying degrees of hearing sensitivity (normal hearing [n= 4], mild-to-moderately severe hearing loss (n= 6), and severe-to-profound hearing loss [n= 3]). Consonants and vowels within CV syllables were grouped according to place of articulation. Thus, an inventory of CV syllables with labial, coronal, and dorsal consonant onsets was created.

Results

77% of predicted frames were confirmed above chance. Additionally, there was no association between pure-tone average and any CV co-occurrence. Finally, co-occurrences that were not predicted by the hypothesis were statistically confirmed in very few instances.

Conclusions

Auditory sensitivity may not influence intrasyllabic organization within CV syllables once infants begin canonical babbling, as the co-occurrences observed are primarily those predicted by the f/c hypothesis.
Physiological Indices of Bilingualism: Oral–Motor Coordination and Speech Rate in Bengali–English Speakers
Authors: Chakraborty Rahul , Goffman Lisa , Smith Anne
Published: March 2008

Purpose

To examine how age of immersion and proficiency in a 2nd language influence speech movement variability and speaking rate in both a 1st language and a 2nd language.

Method

A group of 21 Bengali–English bilingual speakers participated. Lip and jaw movements were recorded. For all 21 speakers, lip movement variability was assessed based on productions of Bengali (L1; 1st language) and English (L2; 2nd language) sentences. For analyses related to the influence of L2 proficiency on speech production processes, participants were sorted into low- (n= 7) and high-proficiency (n= 7) groups. Lip movement variability and speech rate were evaluated for both of these groups across L1 and L2 sentences.

Results

Surprisingly, adult bilingual speakers produced equally consistent speech movement patterns in their production of L1 and L2. When groups were sorted according to proficiency, highly proficient speakers were marginally more variable in their L1. In addition, there were some phoneme-specific effects, most markedly that segments not shared by both languages were treated differently in production. Consistent with previous studies, movement durations were longer for less proficient speakers in both L1 and L2.

Interpretation

In contrast to those of child learners, the speech motor systems of adult L2 speakers show a high degree of consistency. Such lack of variability presumably contributes to protracted difficulties with acquiring nativelike pronunciation in L2. The proficiency results suggest bidirectional interactions across L1 and L2, which is consistent with hypotheses regarding interference and the sharing of phonological space. A slower speech rate in less proficient speakers implies that there are increased task demands on speech production processes.
Genetic Effects on Children’s Conversational Language Use
Authors: DeThorne Laura S. , Petrill Stephen A. , Hart Sara A. , Channell Ron W. , Campbell Rebecca J. , Deater-Deckard Kirby , Thompson Lee Anne , Vandenbergh David J.
Published: March 2008

Purpose

The present study examined the extent of genetic and environmental influences on individual differences in children’s conversational language use.

Method

Behavioral genetic analyses focused on conversational measures and 2 standardized tests from 380 twins (
M
= 7.13 years) during the 2nd year of the Western Reserve Reading Project (S. A. Petrill, K. Deater-Deckard, L. A. Thompson, L. S. DeThorne, & C. Schatschneider, 2006) Multivariate analyses using latent factors were conducted to examine the extent of genetic overlap and specificity between conversational and formalized language.

Results

Multivariate analyses revealed a heritability of .70 for the conversational language factor and .45 for the formal language factor, with a significant genetic correlation of .37 between the two factors. Specific genetic effects were also significant for the conversational factor.

Conclusions

The current study indicated that over half of the variance in children’s conversational language skills can be accounted for by genetic effects with no evidence of significant shared environmental influence. This finding casts an alternative lens on past studies that have attributed differences in children’s spontaneous language use to differences in environmental language exposure. In addition, multivariate results generally support the context-dependent construction of language knowledge, as suggested by the theory of activity and situated cognition (J. S. Brown, A. Collins, & P. Duguid, 1989; T. A. Ukrainetz, 1998), but also indicate some degree of overlap between language use in conversational and formalized assessment contexts.
Head Angle and Elevation in Classroom Environments: Implications for Amplification
Authors: Ricketts Todd Andrew , Galster Jason
Published: March 2008

Purpose

The purpose of this study was to examine children’s head orientation relative to the arrival angle of competing signals and the sound source of interest in actual school settings. These data were gathered to provide information relative to the potential for directional benefit.

Method

Forty children, 4–17 years of age, with and without hearing loss, completed the study. Deviation in head angle and elevation relative to the direction of sound sources of interest were measured in 40 school environments. Measurements were made on the basis of physical data and videotapes from 3 cameras placed within each classroom.

Results

The results revealed similarly accurate head orientation across children with and without hearing loss when focusing on the 33% proportion of time in which children were most accurate. Orientation accuracy was not affected by age. The data also revealed that children with hearing loss were significantly more likely to orient toward brief utterances made by secondary talkers than were children with normal hearing.

Conclusions

These data are consistent with the hypothesized association between hearing loss and increased visual monitoring. In addition, these results suggest that age does not limit the potential for signal-to-noise improvements from directivity-based interventions in noisy environments.
Comparison of Word-, Sentence-, and Phoneme-Based Training Strategies in Improving the Perception of Spectrally Distorted Speech
Authors: Stacey Paula C. , Summerfield A. Quentin
Published: March 2008

Purpose

To compare the effectiveness of 3 self-administered strategies for auditory training that might improve speech perception by adult users of cochlear implants. The strategies are based, respectively, on discriminating isolated words, words in sentences, and phonemes in nonsense syllables.

Method

Participants were 18 normal-hearing adults who listened to speech processed by a noise-excited vocoder to simulate the information provided by a cochlear implant. They were assigned randomly to word-, sentence-, or phoneme-based training and underwent 9 training sessions (20 min each) on separate days over a 2- to 3-week period. The effectiveness of training was assessed as the improvement in accuracy of discriminating vowels and consonants, as well as identifying words in sentences, relative to participants’ best performance in repeated tests prior to training.

Results

Word- and sentence-based training led to significant improvements in the ability to identify words in sentences that were significantly larger than the improvements produced by phoneme-based training. There were no significant differences between the effectiveness of word- and sentence-based training. No significant improvements in consonant or vowel discrimination were found for the sentence- or phoneme-based training groups, but some improvements were found for the word-based training group.

Conclusion

The word- and sentence-based training strategies were more effective than the phoneme-based strategy at improving the perception of spectrally distorted speech.
Nuclear Resonances in Cubic, Hexagonal, and Mixed Phase Cobalt Powders and Thin Films
Authors: Hardy Wilton A.
Published: March 2008

A number of nuclear resonances in ferromagnetic cobalt are reported and identified as originating in hcp crystallographic structure and in associated fault structure. A tentative assignment of these lines has been made to possible stacking fault symmetries by correlating the observed resonances with metallurgical sample treatments.
Report on Ferromagnetic Resonance at the 1960 Conference on Magnetism and Magnetic Materials
Authors: Rado George T.
Published: March 2008

An integrated summary is given of some of the results and physical ideas contained in 16 experimental and theoretical papers on ferromagnetic resonance contributed to the 1960 Conference on Magnetism and Magnetic Materials. The topics discussed include the uniform mode and anisotropy, nonuniform magnetostatic and electromagnetic modes, spin-wave resonance, sublattice effects, paramagnetic “impurities,”spin-wave scattering, rapidly relaxing ions, determination of spin-wave transition probabilities, thermal relaxation, and the theory and use of the “parallel pump” method for measuring relaxation and exchange parameters. Although a complete review of ferromagnetic resonance is not intended, the emphasis is on an organization of this field and on the introductory and explanatory material presented with each topic.
Ferrimagnetic Resonance in Single Crystals of Cobalt-Substituted Manganese Ferrite
Authors: Teale R. W. , Hight M. J.
Published: March 2008

The results of microwave resonance measurements of the gfactor and the first- and second-order anisotropy fields K1/M and K2/M are summarized for crystals with the nominal composition CoxMn1−xFe2O4, where 0 ≤ x ≤ 0.10. In the region 150°K<T<300°K Δ(K1/M) = Ax, Δ(K2/M) = −Bx and g = a+bx. Δ(K1/M) is the cobalt contribution to K1/M; similarly for Δ(K2/M). The results for K1/M are in agreement with published values determined statically on the same crystals. For T = 290°K, 260°K, 230°K, 200°K, 170°K, and 140°K, B is 510,1790, 4600, 10 300, 22 400, and 50 000, respectively. At 260°K the values for a and b are 2.003 and 0.41 respectively, at 9400 Mc;at 17 000 Mc the values are 1.992 and 0.42. For the lower frequency at 170°K the values are 2.004 and 0.64. The two microwavefrequencies were used only above 77°K; in this range the g values are isotropic to better than 0.5%. At 4.2°K the effect of the cobalt upon the variation of resonance field with direction in a(110) plane cannot be accurately described by K1/M and K2/M. The results are compared with the successful theory for the cobaltion substituted into Fe3O4. It appears that modification of the original model is necessary to take into account the differing environment of the cobalt ion when substituted into MnFe2O4.
Microwave Resonance in Tetragonally Distorted Manganese-Iron Spinel
Authors: Overmeyer James
Published: March 2008

A single crystal of tetragonally distorted manganese-iron spinel of composition Mn1.85Fe1.15O4 has been studied by microwave resonance in the temperature range 77–390°K. The anisotropy has tetragonal symmetry,with the c axis hard and the tetragonal a axis (corresponding to the [110] direction in the undistorted cubic structure) easy. The data are analyzed in terms of an anisotropy energy of the form: EA = K1α32+K2α34+K3(α14+α24),wherein α1 and α2 are direction cosines of the magnetization referred to the tetragonal a axes, and α3 is the direction cosine of the magnetization referred to the c axis. The second-order axial component K1/M is approximately 3 kgauss at room temperature and remains relatively constant as the temperature is lowered to 160°K, below which it increases rapidly. The quantity K3/M, which measures the anisotropy in the basal plane, is about −25 gauss at room temperature and increases to a few hundred gauss at 77°K. A temperature independent geff = 2.01 adequately describes the measurements. Linewidths vary from 250 gauss in the tetragonal [110] direction to 400 gauss in the c direction at room temperature and increase with decreasing temperature.
New Characteristic in the Temperature Dependence of Ferrimagnetic Resonance Linewidth in Some Rare-Earth Doped Yttrium Iron Garnets
Authors: Dillon J. F.
Published: March 2008

Measurements have been made of the ferrimagnetic resonance linewidth of YIG doped with each of the rare earths. These results will be presented in full elsewhere. For the most part there is a peak in the ΔH(T) curve at some temperature between 20° and 150°K. The position of this peak varies with the impurity, the frequency, and the crystal direction of the steady field. However,several cases have been observed in which the linewidth increases very rapidly with decreasing temperature down to the lowest temperature reached, about 1.5°K. This behavior occurs over a very narrow angular range. For ytterbium-doped YIG, it is associated with a very mild peak in the field for resonance. For the case of europium there appears to be no anomaly in Hres, though a plot of linewidth against angle shows an increase of about fifteen fold with a half-width of perhaps 1.5°. It is suggested that this anomalous linewidth vs angle and temperature curve, as well as the more generally encountered peak in ΔH(T), represent the excitation of transitions between sublevels of the rare-earth multiplet which approach within an energy comparable to that of a photon of the exciting radiation.
Development of Elongated Particle Magnets
Authors: Luborsky Fred E.
Published: March 2008

The development of permanent magnet materials is briefly reviewed. The present status of fine particle magnets is discussed from the viewpoint of our present understanding and lack of understanding of their behavior. The present methods of preparation and the various theoretical descriptions of the properties of elongated particles are reviewed. New work is presented relating the parameters of preparation to the resulting diameter of the elongated particles prepared by electrolysis into mercury. Rotational hysteresis,coercive force, and coercive force as a function of orientation are reported for particle diameters from 130 A to 305 A. Their behavior is compared to various theoretical descriptions and found to correspond to a noncoherent magnetization reversal mechanism most similar to the chain-of-spheres fanning model rather than the curling, buckling or coherent rotation models. Iron and iron-cobalt alloy particle magnets are described with maximum energy products up to 4.3 and 6.5 million gauss-oe, respectively.
Unidirectional Properties in the Iron-Iron Sulfide System
Authors: Greiner J. H. , Croll I. M. , Sulich M.
Published: March 2008

The unidirectional properties and the nonvanishing rotational hysteresis for applied fields >2K/Is are ascribed to exchange anisotropy between ferromagnetic iron and antiferromagnetic ironsulfide. Torque curves, measured on samples cooled in a magnetic field, depended upon the percentage of iron, temperature, and applied field. Maximum torques at −196°C for 6000 oe increased from 2×106 to 1.5×107 d-cm/cm3 of ferromagnetic Fe for a decrease in iron percentage of 4.5–0.87%. This is attributed to a decrease in particle size with decreasing iron percentage, thereby enhancing the unidirectional properties. The decrease of the sinθ dependence of torque at high fields is explained by a reorientation of the moments of the antiferromagnetic iron sulfide. The fact that a sinθ term is present after a reorientation of the moments in the antiferromagnetic material indicates that the coupling between the moments of the iron and the iron sulfide across the interface remains, but has been realigned. Iron sulfide has a Néel temperature of 340°C and a reordering temperature near 140°C where the spins change their ordering direction by 90°. The significance of the reordering temperature is evident from the rapid decrease in rotational hysteresis as the reordering temperature is approached and also from the absence of an increase in maximum torqueupon cooling in a field from temperatures greater than 150°C.
Magnetic Annealing of “Ticonal” G Magnet Steel
Authors: Zijlstra H.
Published: March 2008

A study was made of magnetic anisotropy and interparticle distance in “Ticonal” G (a dispersion-hardening permanent-magnet alloy) when subjected to heat treatment in a magnetic field. The experimental results agree with a theoretical model in which the precipitate particles are idealized to prolate spheriods which decrease their interfacial free energy by coarsening and their magnetostatic free energy by elongation. It is concluded that the response to thermomagnetic treatment increases with the ratio between the magnetostatic free energy and the interfacial free energy. The interface tension of “Ticonal” G is found to be extremely low, of the order of 1 erg cm−2at the annealing temperature.
Optical and Infrared Spectra of the Ferrites and Garnets
Authors: Wickersheim Kenneth A.
Published: March 2008

A discussion of the variety of applications of spectroscopy to the study of magnetic materials (as restricted to the ferrites and garnets) is presented. Far infrared atomic spectra, infrared vibration spectra, and impurity spectra are discussed as well as the visible and near-visible spectra of the transition metal and rare earth ions. The optical study of the iron-rare earth exchange interaction in the garnets is described in some detail.
Parametric Effects in Magnetoacoustic Resonance
Authors: Comstock R. L. , Auld B. A. , Wade Glen
Published: March 2008

Experimental and theoretical results are presented to substantiate the parametric origin of the excitation of megacycle frequency acoustic modes in a polished YIG sphere by microwave power. A method is described for measuring the acoustic Q using a component of transverse magnetization varying at the acoustic frequency to induce a voltage in a loop placed around the sphere. The response of the magnetostatic acoustic mode system for microwave powers less than that necessary to excite the acoustic oscillation has been investigated. An equivalent circuit of the system is derived which explains the observed results.
Nonlinear Response of YIG
Authors: Hill Robert M. , Bergman Robert S.
Published: March 2008

A small signal study of the second harmonic produced by a small YIG single crystal shows that the anisotropy energy, K1, is the dominant nonlinear term. This should be true for any ferrimagnet for which |K1/(M3ΔH)| > 1. At signal levels above saturation a periodic amplitude modulation of the second harmonic level occurs, which may be due to an exchange of energy between longitudinally and transversely radiating modes.
Magnetization Process of a Helical Spin Configuration
Authors: Enz U.
Published: March 2008

The behavior of a helical spin configuration of a hexagonal crystal in an applied field is discussed for the case where the axis of the helix is identical with the hexagonal c axis and the magnetization vector in each layer is parallel to the basal plane. In a small field applied parallel to the basal plane, a slight deformation of the helix occurs resulting in a small increase in over-all magnetization. If the field surpasses a certain critical value, the helix changes abruptly into a state with high resulting magnetization. In this state the spin directions are oscillating about the direction of the applied field, the magnetization being about 85% of the saturation value. In still higher fields, saturation is reached completely. A helical spin configuration has been found in MnAu2 by Herpin,Mériel, and Villain. We have investigated the properties of the hexagonal oxide (Ba,Sr)2Zn2Fe12O22 which is of the Y-type. The Ba-rich composition is ferrimagnetic and has a preferential plane for the magnetization at all temperatures. The Sr-rich composition has no spontaneous magnetization, but a magnetization equal to the one in the Ba case can easily be induced by an applied field. This behavior can be explained by the assumption of a helical spin configuration. As an other example, we show that the magnetic properties of dysprosium as investigated by Behrendt,Legvold, and Spedding can be explained by assuming a helical spin configuration between 85°K and 178°K. The angle between two neighboring layers is equal to zero at 85°K, the ferromagneticCurie temperature, and increases at higher temperatures. The magnetization process mentioned above is modified slightly in dysprosium by the presence of a strong magnetic anisotropy in the plane. In the presence of this anisotropy the transition between the ferromagnetic state and the helical state turns out to be a first-order transition, which explains the observed specific heat.
On Additivity of Imperfections as Means for Domain Nucleation
Authors: Aharoni A.
Published: March 2008

The theoretical nucleation field is too high to explain experimental observation of domains, even if it is assumed that in a certain region the magnetocrystalline anisotropy constant K is zero. In order to see to what extent the effect of such regions can be additive, a study is reported here of the two one-dimensional cases. In the first case, the regions of K = 0 extend periodically over the whole (infinite) material. In the second case, there are 2 such regions. The periodic case is found to yield somewhat larger nucleation field than the second case. In both cases the reduction in nucleation field with respect to the perfect material is only one order of magnitude for reasonable defect size, and is slightly less than for one defect of the same size.
Analytic Hysteresis Function
Authors: Middleton F. H.
Published: March 2008

An analytic function is proposed in a parametric form which displays the character of an adjustable hysteresis loop. The type of function used was suggested by the phase-frequency characteristic of a conventional phase shift network. There are two parameters in the analytic function, one of which controls the width of the loop, and the other, the steepness of the sides of the loop. These two parameters are related to the conventional magnetic parameters such as coercivity, residual induction, etc., so that one may construct a synthetic loop corresponding to a given experimental loop. The analytic function was used to produce equations for the Fourier series components of b and h in terms of the two parameters. The mathematics is omitted in the paper but the results are given, and an application of the results is made to some experimental data. A typical set of CRO photographs is used to display a family of synthetic loops produced by an analog computer arranged to generate voltages corresponding to the analytic function.
Uniaxial Anisotropy in Polycrystalline Garnets
Authors: Epstein D. J. , Frackiewicz B. , Hunt R. P.
Published: March 2008

In samples of polycrystalline yttrium and lutetium iron garnet which exhibit domain-wall relaxation effects, it is possible to establish uniaxial anisotropy by cooling to low temperature in a magnetic field. This magnetic anneal leads to the development of rectangular hysteresis loops. In lutetium iron garnet,where a particularly strong anneal is found, a uniaxial anisotropy energy of 4500 erg/cc is obtained. After cooling, the easy axis can be shifted in direction by altering the orientation of the applied field; the shift in axis occurs with a finite time constant (order of 15 sec for LuIG).
Exchange Anisotropy in Stainless Steel
Authors: Meiklejohn W. H.
Published: March 2008

“Nonmagnetic” stainless steel is a paramagnetic material at room temperature with a face-centered cubic lattice structure. It has been shown by Kondorsky and Sedov that the susceptibility has an anomaly at 40°K which is quite characteristic of an antiferromagnetic transition. This result suggested to us that cold working such a material to transform part of the material to the ferromagnetic body-centered cubic structure might yield a shifted hysteresis loop, if the bcc structure is in exchange contact with the fcc material.

A cold-worked (swaged) type 347 stainless steel did develop a shifted hysteresis loop when cooled in a magnetic field from room temperature to 4.2°K, while the hysteresis loop was symmetrical when the materialwas cooled in a zero magnetic field.

We also measured the shift of the hysteresis loop as a function of temperature and found that the shift disappeared at 40°K, which is in agreement with the susceptibility measurements of Kondorsky and Sedov.
Frequency Dependence of Ultrasonic Wave Attenuation in Armco Iron and Low-Carbon Steel
Authors: Martius U. M. , Bratina W. J.
Published: March 2008

The ultrasonic wave attenuation in Armco iron and low-carbon steel was measured vs increasing and decreasing external magnetic field strength (0–400 oe) at frequencies between 1 and 7 Mc. The magnetic component of attenuation was found to increase with frequency. The structure sensitivity of the magnetic loss mechanism was studied by changing the dislocation density. A continuous decrease of attenuation with increasing field is characteristic for annealed material, and a pronounced maximum followed by a decrease for deformed material. The results are discussed on the basis of models of structure-sensitive magnetic properties advanced by Néel and recent work by Kersten. These models are unable to explain consistently all experimental observations. The possibility of loss processes within stationary domain walls was considered.
Magnetoresistance and Magnetic Switching in Permalloy Films
Authors: Coren R. L. , Juretschke H. J.
Published: March 2008

Magnetoresistance measurements have been used to study the magnetic properties of Permalloy films. Resistivities parallel and transverse to the current were measured simultaneously as the applied magnetic field was varied in magnitude or direction in the film plane. The results are discussed in terms of a representation in which the resistivity components are regarded as Cartesian coordinates. This representation is independent of the current direction relative to any magnetically preferred orientations in the film. The statistical,domain-wall, switching model of Conger and Essig is extended to include the situation in which the field and easy magnetic axis are not parallel, and a switching profile is constructed which gives a unified representation of the domain wall and coherent rotational switching response of a uniaxial film to an applied field. The incidence of moving domain walls under certain field conditions is discussed with the help of this profile,and it is shown that the magnetoresistance curves may be understood in terms of the magnetic changes.
Generation of Microwave Electromagnetic Radiation in Magnetic Materials
Authors: Rowen J. H. , Eggers F. G. , Strauss W.
Published: March 2008

A novel method of generating microwave and millimeter wave radiation in magnetic materials through the influence of high-intensity mechanical vibrations is described. Measured values of the static strain dependence of cubic ferrite materials are used to illustrate the principle, and arguments are presented extending this method to millimeter wave generation in antiferromagnetic materials.
Phase Shift Studies in Ferrite-Dielectric Loaded Coaxial Lines at 2200 Mc
Authors: Rowley J. J.
Published: March 2008

Results are presented of an experimental study which was undertaken to determine the parameters which affect total and differential phase shifts in ferrite-dielectric loaded coaxial lines. The dependence of phase shift per unit length on the parameters of dielectric angle, ferrite cross-sectional area, and dc magnetic field are shown for a 78-in. coaxial line. These experimental results are compared to those computed by Button for a 158-in. coaxial line and found to agree quite well qualitatively. Differential phase shifts of 300° per db loss were obtained for the best experimental results, and the study has shown that the theory developed by Button correctly predicts the parameters necessary to obtain large differential phase shift in ferrite-dielectric lines.
On the Nature of the Magnetic Couplings in Transitional Metals
Authors: Friedel J. , Leman G. , Olszewski S.
Published: March 2008

This paper suggests a simple model of magnetism for transitional metals which is somewhat intermediate between Heisenberg's atomic model and Stoner's band model. Starting with a paramagneticd band, described in the tight-binding approximation and with equal population of both spin directions, exchange interactions are introduced. They are shown able to produce localized magnetic moments, by attracting locally the (traveling) electrons of one spin direction at the expense of the others. A simple condition is obtained for such magnetic moments to appear spontaneously;it is shown to be fulfilled in many transitional metals. With the use of general results obtained recently by the authors and by others, it is then shown that each of these magnetic moments, if produced alone, should extend over a certain region in space, and should be surrounded by “fringes” of spin polarization with an alternating sign. The size of the central region and the wavelength of the fringes are related to an average wavelength of the Fermi electrons, and thus to the filling of the d band. The sign and the strength of the coupling between magnetic moments centered on neighboring atoms is deduced from the extent of their overlap. The magnetic couplings observed in the first transitional series are shown to be in fair agreement with this model. The conditions prevailing in the other series and in alloys are also discussed. This model is compared to those put forward by Zener, Yoshida, and Slater. It is emphasized that it leads to the equivalent of chemical exchange integrals between the moments of neighboring atoms without losing the characteristic features of the d band, especially its high electronic specific heat and Pauli paramagnetism.
Experimental g′ and g Values of Fe, Co, Ni, and Their Alloys
Authors: Meyer A. J. P. , Asch G.
Published: March 2008

The magnetomechanical ratio g′ and the spectroscopic factor g were measured on same samples of iron and nickel. The g factors were also measured for some Fe-Ni, Fe-Co, Co-Ni, alloys. The experimental values of g and g′ are used to check the Kittel-Van Vleck relations, whose exact form 1/g+1/g′ = 1 appears well satisfied. It is shown that the effective magnetomechanical ratio geff′ of an alloy, which is given by the quotient of the total magnetic moment to the total angular momentum of the system, converts itself by means of the relation 1/g+l/g′ = 1 to the formula of Tsuya and Wangsness, which gives the effective splitting factor geff of a two-sublattice system. The calculated curves of geff agree with the experimental points for the Fe-Ni, Fe-Co, Co-Ni alloys. Using the measured values of g and g′, one calculates the mean spin moment contribution of the ferromagnetics, with a mean electronic number higher than 26.8,which crystallize in fcc or hexagonal structures: the mean spin moment decreases linearly by increasing electronic number with a slope of −1.05μB/electron.
Magnetic Characteristics of Some Intermetallic Compounds between Manganese and the Lanthanide Metals
Authors: Cherry L. V. , Wallace W. E.
Published: March 2008

The lanthanide metals have been observed to form a large number of intermetallic compounds with the transition metalsof the first long period. The compounds have compositions corresponding to the formulas AB2 and AB5, in which A represents the lanthanide and B is Fe, Co, Ni, or Mn. In previous studies[K. Nassau, L. V. Cherry, and W. E. Wallace, J. Phys. Chem. Solids 16, 123 and 131 (1960)] the A Co5 compounds were found to exhibit unusual magnetic behavior. The present study, which deals with the seven isomorphous A Mn5 compounds in which Ais Sm, Gd, Tb, Dy, Ho, Er, and Y, was undertaken to ascertain whether this is also the case when the B component is Mn. The magnetization-temperature behavior of these compounds has been investigated between 80–550°K. Curie points were observed in all cases, the Curie temperature diminishing steadily with increasing atomic number from 465°K for GdMn5 to 415°K for ErMn5. The Curie temperature for YMn5 was found to be 490°K. For all the compounds, except YMn5, the magnetization increases rapidly with decreasing temperature near 80°K, suggesting the existence of a second Curie point. This may be caused by the onset of the alignment of the lanthanide moments or, since there are at least two crystallographically distinguishable Mn's present,to ordering of the moments of a second type of Mn. Saturation magnetizations are presented for 80 and 298°K. The values (in Bohr magnetons per A Mn5 unit) at 80°K range from 1.72 for SmMn5 to 6.23 for GdMn5. The corresponding value for YMn5 is 2.21. These data seem to indicate that the lanthanide moments are aligned in some way at low temperatures, but knowledge of the details of the manner of coupling must await further work.
Magnetic Moments of Compounds of Cobalt with Rare-Earth Elements Having a Cu5Ca Structure
Authors: Nesbitt E. A. , Williams H. J. , Wernick J. H. , Sherwood R. C.
Published: March 2008

Recently, the compound Co5Gd was shown to have antiferromagnetic coupling. The present work is on compounds of this type in which most of the rare-earth elements have been substituted for gadolinium and copper has been substituted for some of the cobalt. The rare-earth elements which have a high magnetic moment (gadolinium, terbium, dysprosium, holmium, erbium,thulium) have an effect on the magnetization vs temperature curve which is startling. The moment is greatly reduced in the vicinity of 0°K in the presence of one of these elements, in contrast to the high moment obtained when yttrium or a low-moment rare-earth element (cerium, praseodymium, neodymium, samarium)is present. As a result of these measurements, we may think of the magnetic structure of most of the compounds of cobalt with a rare-earth element as consisting of a sublattice of the rare earth whose magnetic moment is in opposition to that of the sublattice of the cobalt atoms. All of the compounds conform to this picture with reasonable accuracy except those which contain praseodymium and neodymium. In these two cases, the moment of the compounds is actually increased but the reason for this behavior has not been determined. The presence of compensation points in the magnetization of some of these materials has been demonstrated experimentally.
Ferromagnetic Phase of Mn-Al
Authors: Campbell Robert B. , Julien Carl A.
Published: March 2008

The metastable, ferromagnetic, tetragonal phase in the Mn-Al system has been obtained by isothermal transformation of a high-temperature phase. Transmission electron micrographs of specimens of this phase so obtained (bulk Hci = 1130 oe) show striations of light (transmitting) and dark (non-transmitting) material. The striations are presumed to arise from stresses induced by the transformation and/or cooling. Transmission electron diffractograms contain individual patterns both with and without superlattice reflections. Respective patterns reveal axial ratios of 0.90 and 0.94, and are correlated with the dark and light areas of the micrographs. From diffraction data it is concluded that the trace of the boundary between the light and dark regions coincides with a projection of the c axis. The possibility of coherency as a mechanism for the high coercive force, analogous to CoPt, is discussed. The type of cooperative atomic interaction as related to the shift in the axial ratio is also discussed.
Demagnetization of Twistor Bits
Authors: Barrett W. A.
Published: March 2008

The storage of binary information in twistor wire is complicated by the presence of demagnetizing fields resulting from the open flux path structure of this device. These fields modify the writing threshold of each bit and contribute an interaction with neighboring bits on the same wire. The effect of these demagnetizingfields has been measured with a search-coil technique. A simple procedure consisting of a coincident-current bit select followed by a single-current read select is used to form and “erase” the magnetized regions. It is found that the shape of the magnetized regions thus formed are a complex function of the two currents used and that the bits are not fully erased by the single current. The results suggest that demagnetization must be reduced by reducing thickness and/or bit density unless a more complex solenoid structure can be found to control the magnetization of the bit regions.
Diffusion Reactions in the Aging of 4-79 Molybdenum Permalloy
Authors: Tolman E. M.
Published: March 2008

Measurements of coercive force have been used to follow the low-temperature aging of 4-79 molybdenum Permalloy twistor wire. Twistor wire samples were annealed for varying periods of time at temperatures ranging from 119 to 300°C. This treatment resulted in decreases in coercive force with time which indicated the presence of three distinct reactions. The first reaction, associated with a stress relief anneal, was too rapid to measure. A second reaction, characterized by an exponential decrease in coercive force over the 119–200°C range, was found to fit first-order behavior at 119°C. Its energy of activation was found to be 35.8 kcal/mole or about 1.6 ev. This is the same value as that obtained by Clarebrough from release of energy studies below 300°C as the energy for the disappearance of vacancies in plastically deformed nickel. The 4-79 diffusion reaction appears to result from the same cause. From 119 to 300°C, evidence of a rapid third reaction was observed. Polygonization, as found in an x-ray examination of cold-worked 4-79 alloy heated at 400°C, appears to explain the development of a second easy direction of magnetization in the material.
Initial Permeability Characteristics of Vanadium-Doped Manganese-Zinc Ferrites
Authors: Shichijō Yūzō , Tsuya Noboru , Suzuki Kōki
Published: March 2008

The basic composition of manganese-zinc ferrites used in this experiment is represented by (MnO)27(ZnO)20 (Fe2O3)53. When doped by a small amount of vanadium and calcium, a significant reduction of high-frequency losses has been observed. Measured toroidal specimens were prepared by standard sinteringtechniques, and special precautions have been taken to maintain the sintering temperatures within ±2 degrees. Initial permeability μ, μ−1 tanδ, and the hysteresis coefficient h10 were measured by a Maxwell bridge at room temperature. In these experiments it was found that, under certain sintering conditions,losses are minimized by the use of adequate amounts of vanadium doping yielding less than 3×10−6 and 20 of μ−1 tanδ and the hysteresis coefficient h10, respectively. The loss analysis, granular structure observation and electrical resistivity measurements were also performed.
Flux Distribution in Ferrite Cores under Various Modes of Partial Switching
Authors: James R. H. , Overn W. M. , Lundberg C. W.
Published: March 2008

This paper describes the flux distribution in a ferrite core after partial switching to the same flux density by three different methods: (1) by applying a fixed pattern of alternate-polarity pulses with diminishing amplitude, (2) by amplitude limiting, and (3) by time limiting. Discontinuities in the residual magnetization curve in the first case show the existence of regions of oppositely-directed magnetization. A comparison of the curves shows that the time-limited state can be represented by a model consisting of a large number of regions magnetized in alternate directions.
Exchange Inversion in Mn2−xCrxSb
Authors: Cloud W. H. , Bither T. A. , Swoboda T. J.
Published: March 2008

Compounds of the form Mn2−xCrxSb show a first-order ferrimagnetic to antiferromagnetic phase transitionwith decreasing temperature. Sublattices composed of the three adjacent ferrimagnetically aligned (001)planes Mn(II)-Mn(I)-Mn(II) are ferromagnetically ordered above the transition temperature Ts and antiferromagnetically ordered below Ts. The exchange interaction between these sublattices changes sign at a critical interlayer distance. The discontinuous change in interlayer distance at Ts is proportional to the square of the magnetization of the sublattice in agreement with Kittel's conclusions.
Magnetic Anisotropy and Electrical Resistivity in Exchange Inversion Compounds
Authors: Jarrett H. S. , Bierstedt P. E. , Darnell F. J. , Sparks M.
Published: March 2008

Magnetic anisotropy and electrical resistivity have been determined for several materials of composition Mn2−xCrxSb, which exhibit a ferrimagnetic to antiferromagnetic phase transformation with decreasing temperature. Magnetocrystalline anisotropy is similar in its temperature behavior to that of Mn2Sb with slight differences attributed to changes in magnetic moment of the Mn sublattices. Resistivity is attributed to electron-magnon scattering. The magnetocrystalline anisotropy at the two Mn sites of nearly equal magnitude but opposite sign is consistent with the small anisotropy of the magnetoresistance.
Antiferromagnetic Resonance in (Cr2O3)1−x·(Al2O3)x Single Crystals
Authors: Foner Simon
Published: March 2008

Results of pulsed field antiferromagnetic resonance (AFMR) experiments are briefly summarized for the mixed crystal system (Cr2O3)1−x·(Al2O3)x as a function of temperature, and X, where X = 0.003, 0.006,0.008, 0.06, 0.1, 0.2, and 0.9. The temperature dependence of the critical field, (2λK)12, for pure Cr2O3 and X = 0.1 are compared in detail. The increase of (2λK)12 at 4.2°K from about 59 kilogauss for Cr2O3 to 79 kilogauss for X = 0.1 is attributed to a reversal in sign and rapid increase in magnitude of the effective crystalline field contribution to the anisotropy energy as X is increased. AFMR linewidths from 800 to 2000 gauss were observed, but for X≤0.2 the linewidth was almost independent of temperature for each composition. The decrease of Néel temperature with increase of X is also summarized.
Structure of Nickel Chromite
Authors: Prince E.
Published: March 2008

Nickel chromite is a normal spinel whose structure has a tetragonal distortion below about 310°K. The structure parameters have been determined by neutron diffraction at 77°K, at which temperature the c/a ratio of a face-centered unit cell is 1.04. The space group is I41/amd with four Ni ions in positions 4(a), eight Cr ions in positions 8(d), and 16 O ions in positions 16(h) with y = 0.239 and z = 0.392. The two independent Cr-O distances are 1.98 A and 1.99 A, indicating that the octahedron is not greatly distorted. The tetrahedron around the nickel is elongated by nearly 14% parallel to the c axis. Below a Curie temperature of about 65°K, nickel chromite has a small ferromagnetic moment. The neutron diffraction pattern at 4.2°K shows extra peaks which can be indexed on the basis of a primitive cell having the same dimensions as the body-centered chemical cell. The intensities of these peaks cannot be accounted for by any simple model for the magnetic structure. In fact, a systematic search of possible structures belonging to magnetic space groups with symmetries as low as classes m′m′2 and mm′2′ has failed to turn up any structure which is consistent with the diffraction data.
Effect of Chemisorbed Hydrogen on the Magnetization of Nickel at Low Temperatures
Authors: Dietz Robert E. , Selwood P. W.
Published: March 2008

The saturation magnetization of nickel particles in the range 10–100 A has been determined by extrapolating from magnetizations measured at 4.2°K in fields up to 104 oersteds. Measurements have been made prior to, and after, the admission of hydrogen to the nickel at room temperature. The nickel is supported on silica in the manner familiar in heterogeneous catalysis. The number of d electrons paired per hydrogen atom adsorbed has been calculated from the fractional change in saturation magnetization assuming the magnetic moment per atom of nickel to be 0.606 Bohr magneton. The ratio of d electrons paired to hydrogen atoms adsorbed has been shown to be less than one. On sintered samples in which the average nickel particle diameter is 40–80 A the ratio is about 0.7. On smaller nickel particles the ratio may be less. This ratio does not appear to be sensitive to surface coverage. The fact that the ratio of d electrons paired to hydrogen atoms adsorbed is less than one is considered evidence for a localization of the electronic interaction between adsorbent and adsorbate.
Effects of High Temperature on Magnetic Properties of Core Materials
Authors: Pasnak Michael , Lundsten R. H.
Published: March 2008

An experimental study was made of the effects of temperature on the dc and 60 cps magnetic properties of the following alloys: Orthonol, 4-79 Mo Permalloy, AEM 4750, L- and Z-Silectron, Transformer A, Audio Transformer A, 11.7 Alfenol, 15.5 Alfenol, Thermenol, 7-70 Perminvar, and Supermendur.

The results indicate that, in general, an increase in temperature decreases the coercive force and the maximum and residual inductions. Maximum and initial permeabilities increase with increasing temperature until the Curie temperature is approached, then they decrease. The initial permeability generally reaches a maximum at a lower temperature than does the maximum permeability.
Angular Variation of the Coercivity of Partially Aligned Elongated Ferromagnetic Particles
Authors: Wohlfarth E. P.
Published: March 2008

The angular variation is considered for a number of models assuming coherent or incoherent magnetization reversals, and some application is made to experimental data.
Magnetism of Submicroscopical Iron Particles
Authors: Kronenberg Klaus J.
Published: March 2008

The magnetic fields around submicroscopical iron particles were tested with iron oxide colloid in an electron microscope. The colloid particles usually spread evenly by diffusion. Magnetic fields of several hundred oersteds are required to concentrate the colloid particles visibly at certain spots. We found colloid around iron particles concentrated to various degrees. The colloid was attracted less by smaller particles. The smallest particles did not attract any colloid.

The particles were measured and grouped into three following categories: (a) Particles with strong, all around colloid attraction, indicating many domains. Stem volume of the dendritic particles much bigger than 109 A3, (b) Particles with colloid attractions at spots, indicating one or a few domains. (c) Particles without colloid attraction, indicating no well-developed domains. Stem volume much less than 109 A3.
Novel Light-Weight Moldable Permanent-Magnet Material
Authors: Mendelsohn L. I. , Norman R. S.
Published: March 2008

A novel, light-weight, moldable permanent-magnet material is described. Elongated-single-domain (ESD) particles of iron-cobalt are coated with a thermosetting plastic which serves as matrix. The particles are aligned while the plastic is in a liquid phase. The matrix is then solidified, and the agglomerate ground to a −30 mesh freeflowing powder. Each of the particles of this powder consists of submicroscopic elongated aligned particles. The freeflowing powder can then be directionally pressed in conventional presses to produce magnets of complex shape held to precision dimensions. Energies of 2.0×106 gauss-oersteds have been achieved in magnets whose density is 4 g/cm3 and whose temperature coefficient is 0.008%/°C. The material's properties make it well suited to applications where a light-weight, high energy, precision-dimensioned easily fabricated magnet, capable of withstanding adverse environmental conditions is required. An excellent application of this material is the moving-magnet-instrument rotor.