bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferrite Films Prepared by Pyrohydrolytic Deposition
Authors: Gleason F. R. , Watson L. R.
Published: April 2005

Ferrite films of a nickel-zinc-cobalt composition have been deposited by pyrolytic hydrolysis of metal inorganic salts. The object of the research described in this paper was to deposit these films with a composition like that of a bulk ferrite of particular magnetic properties, and to evaluate the films in terms of structure, composition, and magnetic properties.

The films are prepared by atomizing a mixed solution of the metal chlorides into a reaction tube heated to 800°C. The metal ion concentration in the starting solution is compensated to allow for excessive and varying loss of the constituents during the film-forming process. The method used for determining the amount of starting solution compensation will be discussed along with a detailed description of the experimental apparatus.

The films prepared by this technique exhibit the ferrite spinel structure, as is evidenced by x-ray diffraction data.

A value of 100 for the initial permeability of the films was measured by observing the film B-H relationship. A study of film density and porosity was made from photomicrographs of the film cross section and from the weight of film deposited. These properties were compared to those of the bulk ferrite of like composition, and similar values were obtained.
Optically Observed Exchange Splittings in Antiferromagnetic Cr2O3
Authors: Wickersheim K. A.
Published: April 2005

Well-defined exchange splittings of the R lines of Cr3+ in Cr2O3 have been observed in absorption at low temperatures. The majority of the transitions originate on the lowest (Ms=−32) component of the A24 (ground) state and terminate on the four (exchange split) components of the two E2 levels. The lines show strong polarization effects, the outer two components of the four line group appearing in the perpendicular spectrum (E⊥c axis) and the inner two components appearing in the parallel spectrum. From the observed polarizations and from relative intensity measurements the identity of each of the components has been deduced. On the basis of the identifications made, the exchange splitting of the R1 doublet is approximately 183 cm−1 and that of the R2 doublet is approximately 139 cm−1. A ground-state splitting of 245±20 cm−1 is obtained from a weak line originating on the Ms=−12 (A24) level. The trigonal field (plus spin orbit) splitting of the E2 levels can also be deduced from the spectrum. The splitting would appear to be very small (of the order of 1 cm−1) compared with that of Cr3+ in ruby (29.6 cm−1) and of the opposite sign.
Microwave Modulation of Light Using Ferrimagnetic Resonance
Authors: Anderson L. K.
Published: April 2005

The operation of an optical modulator based on the time-varying optical Faraday rotation produced by the precessing magnetization in a magnetic material is analyzed, and experimental results given for an X-band modulator using a thin disk of yttrium iron garnet. The analysis is valid for both lumped and traveling-wave magneto-optical interactions, and leads to a figure of merit on the basis of which some presently available ferrimagnetic materials are compared.
Zeeman Effect of the R Lines in Cr2O3
Authors: Stager C. V.
Published: April 2005

We have investigated the Zeeman effect of the R lines at 4.2°K in fields up to 88 kOe. The magnetic field has been applied both parallel and perpendicular to the C3 axis. When the external field is applied along the C3 axis, all of the lines split into two components. No splitting is observed in the perpendicular orientation. As the Kramer's degeneracy has already been lifted by the exchange field, the splitting is attributed to the removal of a sublattice degeneracy. It is well known that the spin system of Cr2O3 will flip when a critical field of about 59 kOe is applied along the C3 axis at 4.2°K. The spin-flop phenomenon has been seen in the optical spectra. From the splitting above the critical field there is tentative evidence of an anisotropic exchange interaction.
Far-Infrared Spectra of Holmium, Samarium, and Gadolinium Iron Garnets
Authors: Sievers A. J. , Tinkham M.
Published: April 2005

Far-infrared (10–100 cm−1) spectroscopic transmission measurements have been made on sintered powder samples of ferrimagnetic holmium, samarium, and gadolinium iron garnets. Both single-ion transitions and also the Kaplan—Kittel exchange resonances have been observed in HoIG and SmIG. A breakdown of selection rules permits the observation of the single-ion transitions, in which the effective angular momentum of a single rare-earth ion changes in the presence of the crystalline electric and iron exchange fields. Because no magnetic absorption is observed in GdIG, single-ion transition probabilities appear to be governed by the effect of the local crystalline electric field on the rare-earth ion, as expected theoretically. Experimentally, one can distinguish the collective modes because their resonant frequencies are more temperature dependent than those of the single-ion transitions.
Magnetoelectric Effects in Cr2O3 and (Cr2O3)0.8· (Al2O3)0.2
Authors: Foner Simon , Hanabusa Mitsugu
Published: April 2005

Magnetic field induced magnetoelectric (ME) effects in Cr2O3 and (Cr2O3)0.8·(Al2O3)0.2 have been examined with an ac method as a function of temperature and magnetic field. The ME effect parallel to the c axis reverses in sign at low temperatures for both materials, and is linear in H for all temperatures up to the spin-flop field HC after which the ME effect approaches zero. The temperature dependence of the extrema of (dE/dH) vs H leads to a measure of HC vs T which agrees with earlier antiferromagnetic resonance and magnetic moment data in similar materials. Complete reversibility of the ME effect is observed when the magnetic field exceeds HC and then returns to lower values, thus demonstrating a stable memory of the domain distribution introduced during magnetic annealing. Brief remarks are made on the angular dependence of the ME effect, and indications of nondiagonal contributions in the vicinity of HC are mentioned.
Ferrimagnetic Resonance Anomalies in Cobalt-Substituted Manganese Ferrite Crystals
Authors: Teale R. W. , Clarke B. H.
Published: April 2005

Microwave resonance measurements are reported near 16.8 Gc in the temperature range 1.5° to 77°K for a crystal of composition Co0.005Mn0.995Fe1.99O4. Sharp peaks were observed in the field for resonance and linewidth as a function of orientation below 10°K. The applied field directions for which these peaks occur lie on cones with axes along [111] directions and semivertical angle 34°. At higher temperatures the peaks in ΔH split into two and this splitting increases with increasing temperature. The general resemblance of the behavior below 10°K to that of YIG doped with certain rare-earth ions is pointed out and by analogy, the peaks are attributed to near crossovers in the low lying energy levels of the cobalt ion. A model for relaxation which was useful for nickel ferrite containing Fe2+ ions and for rare-earth doped YIG is applied qualitatively and on this basis the minimum energy level splitting at the near crossover is tentatively de-deduced to be 11 cm−1. The occurrence of crossovers at the angles concerned is not predicted by models for the Co2+ ion which have been used previously in theories of the magnetocrystalline anisotropy of spinel ferrites containing cobalt.
Interactions in Various Magnetic Compounds
Authors: Gorter E. W.
Published: April 2005

Susceptibility measurements on single crystals of KFe11O17 show an anomalous antiferromagnetic behavior, which we propose to call antiferrimagnetism. The behavior follows from Weiss field theory on a simplified (i.e., two-sublattice) model.

The magnetic structure of K2NiF4 has been determined by neutron diffraction by Legrand and Plumier at C.E.N., Mol (Belgium). Measurements on their single crystal show that χ∥ and χ⊥ become nearly equal at ≈100°K, i.e., far below the temperature where χ is maximum. This is believed to be due to a gradual breaking up of the long-range order in the basal layers. Results obtained on powders of La0.5Sr1.5MnO4 and La1.5Sr0.5CoO4 are also given.

Pure polycrystalline samples of EuS, EuSe, and EuTe with rocksalt structure show θ values of +16, +6, and −7°K; EuTe has a Néel temperature at +11°K. The ferromagnetism of EuO, EuS, and EuSe is due to a predominant direct positive exchange interaction Eu-Eu, the antiferromagnetism of EuTe to a predominant next-nearest neighbor superexchange interaction Eu-X-Eu. Neither interaction is believed to change sign in the series. Measurements of M vs T at various field strengths are in very good agreement with Weiss field theory.

Oxidic spinels with diamagnetic ions in A sites have so far shown negative θ values. The substances Ge[Fe2]O4, Ge[Co2]O4, and Ge[Ni2]O4 have θ values of −15, +90, and 0°K, respectively. The materials Ge[Ni2−2δLiδFeδIII]O4 have positive θ values, increasing linearly with δ to 180°K for δ=0.5. Here the Ni2+–Fe3+ interaction must be positive and this interaction is thought to be a direct one, as is discussed.
Magnetism of Piezoelectric Ga2−xFexO3
Authors: Nowlin C. H. , Jones R. V.
Published: April 2005

The magnetic moments and susceptibilities of the piezoelectric-ferromagnetic compounds Ga2−xFexO3 have been measured over a temperature range from 4.2° to 350°K. The saturation moment at 0°K and the Curie temperature follow a linear compositional relationship. The magnetic properties of these compounds are sensitive to heat treatment. In the vicinity of the Curie temperature, the magnetization follows a (Tc−T)2 law. At low temperatures, the deviation in the magnetization follows an exponential of the form exp (−98.8°K/T). In the paramagnetic region, the Curie constants for these substances differ radically from values expected for an ensemble of S state ferric ions. From the experiments reported here, it seems that one must assume in these compounds that the ferric ions have an exceedingly strong local crystalline interaction.
Single-Domain Properties in Hexagonal Ferrites
Authors: Mee C. D. , Jeschke J. C.
Published: April 2005

Barium ferrite platelet-shaped particles have been prepared with a diameter of 0.1 microns, which is an order of magnitude smaller than those obtained by conventional sintering and regrinding techniques. The preparation technique used has been optimized to produce the complete ferrite with σs=68 emu/g. Due to the small particle size, extremely high intrinsic coercive forces have been obtained, (Hc=5350 Oe), in good agreement with the value calculated from the Stoner-Wohlfarth (SW) coherent rotating model for single-domain noninteracting particles when shape and crystal anisotropy are both taken into account. Furthermore, the measured hysteresis loop for an unoriented sample agrees well with the theoretical SW loop. Similar hysteretic magnetization properties have been obtained in strontium ferrite. The single-domain nature of these powders is also demonstrated by their temperature dependence of coercive force where little change is obtained over the range −200° to +150°C. An estimate of the relative interaction field magnitude for the small particles of barium ferrite has been obtained by comparing its initial anhysteretic susceptibility with that of an acicular iron oxide powder.
Modified Strontium Ferrite, a New Permanent Magnet Material
Authors: Cochardt A.
Published: April 2005

A review of the magnetoplumbite magnet development is given from the early magnets of Takei to the recent high energy barium ferrite magnets of Tomholt. A method for rapidly testing a large number of ferrite permanent magnet specimens is described which was used on several thousand specimens. The results are summarized for portions of the ternary systems M1O·M2O·Fe2O, where M1 and M2 stand for Ba, Sr, Pb, or Ca. A modified strontium ferrite magnet could be developed which appears to have a higher magnetic energy than any other oxide magnet material previously known. Typical values are: Br=4100 G, IHc=3000 Oe, (BH)max=4.0 mgo. At lower coercive forces and under careful laboratory conditions, modified strontium ferrite magnets can be prepared with a (BH)max approaching 5 mgo. A number of permanent magnet applications are mentioned for which the new material is most suitable.
Absorption Phenomena in Parallel-Pump Experiments
Authors: Courtney W. E. , Clarricoats P. J. B.
Published: April 2005

Experimental results using longitudinally pumped YIG at X band are described. It is shown that absorption as a function of applied field depends on the manner in which the YIG sample is supported. When the sample is loosely mounted the absorption characteristics show evidence of magnetoelastic coupling. A value for the exchange constant determined under this condition is in good agreement with that obtained by Turner. When the sample is more rigidly mounted the absorption characteristic changes markedly and it appears that the magnetoelastic coupling is suppressed. A discontinuity in the absorption characteristic is also observed at a field strength well below the critical threshold value. Differences in absorption between up and down cycles of the sweep field are also reported.
Study of Magnetoelastic Interactions by Parallel Pumping
Authors: Olson Frank A.
Published: April 2005

Magnetoelastic interactions, the coupling of spin waves with phonons, have been studied in single crystals of yttrium iron garnet using the parallel pumping technique. Observations of the coupling have been made for various temperatures and crystalline orientations at 4.75 and 11.6 kMc.

An increase in the threshold field for spin-wave excitation occurs when there is magnetoelastic coupling, and the form of the increase provides a line shape for the spin-wave-phonon interaction. From the magnitude, width, and location of the interaction line are found the acoustic Q, the magnetoelastic constant b2, and the spin-wave exchange constant. The quantities obtained (i.e., Q=2×104 and b2=4.7×106 ergs/cm3 at room temperature) are in reasonable agreement with those from lower frequency measurements, assuming a f−1 variation for Q. The magnetoelastic constant b2 is found to increase with decreasing temperature. Correlation of the temperature variation of b2 with theoretical predictions is good and, if the comparison is valid, provides an evaluation of the higher-order magnetoelastic constant b5.
Magnetostriction Constants from Ferromagnetic Resonance
Authors: Smith A. B. , Jones R. V.
Published: April 2005

The saturation magnetostrictive constants of a magnetic material may be determined by means of ordinary ferromagnetic resonance. For small strains, the magnetic field required for resonance at a given frequency is a linear function of the applied uniaxial stress. The magnitude of this shift may be directly related to the magnetostrictive constants of the substance under investigation. The constants for YIG, YIG doped with Er3+, YIG doped with Yb3+, nickel ferrite, and nickel ferrite doped with cobalt have been measured by this new technique in a temperature range from 77° to 350°K. Where comparisons are possible, the results agree quite well with previous measurements. In particular, the measured magnetostrictive constants of YIG are in good agreement with values that have been obtained from magnetoacoustic and strain gauge experiments.
Magnetoelastic Coupling Constants of Terbium and Europium Iron Garnets
Authors: LeCraw R. C. , Kasuya T.
Published: April 2005

The purpose of this paper is twofold: (1) to present data on the magnetoelastic constants of rare-earth iron garnets, a subject which for various reasons has been little studied thus far, and (2) to describe a new method for obtaining these constants which is applicable to many ferromagnetic insulators and does not require the use of strain gauges. The new method was developed from a study of the coupling introduced between long wavelength acoustic modes and long wavelength spin-wave modes by ions in which the orbital moment is not quenched, such as rare-earth ions, Co2+, and Fe2+. The effect of the coupling caused by such ions is observed as a magnetic field dependence of the resonant frequency of an acoustic resonator made from the given material, even above dc saturation. The acoustic Q above dc saturation is also field-dependent. A theory has been obtained which explains the observed field dependences of both v(H) and Q(H) as well as other important features of the magnetoacoustic interaction. It will appear elsewhere.1

One of the results of this theory is a relation between the cubic magnetoelastic constants, B1 and B2, and the acoustic resonant frequency v of a thin disk vibrating in a thickness shear mode. For a (110) disk with the external field H0 in the plane along [100] and the rf driving field perpendicular to the disk, we obtain ν=ν∞(1−B222c44MHeff),where Heff=H0+Hanis+4πM, and c44 is the usual shear elastic modulus, which may be obtained directly from v∞ and the thickness of the disk. Equation (1) applies to the mode with displacement along [100]. B1 is obtained similarly, only now H0 is along [110] in the plane, and the shear displacement is along [110]. Here we have ν=ν∞(1−B122c44MHeff). All data thus far have given excellent fits to these equations as Heff is varied, making it easy to obtain the unknown constants. It should be noted that Eqs. (1) and (2) are high-temperature approximations and at low temperatures will not in general be as simple.

For TbIG and EuIG at room temperature we find the following (all in ergs cm−3): For TbIG, |B1|≤3.5×106, |B2|=30×106; and for EuIG, |B1|=45×106 and |B2|≤4.2×106. The signs must still be determined from strain gauge measurements. The observed reversal of the magnetoelastic anisotropy (ratio of B1 to B2) is being investigated, as well as the temperature dependences of B1 and B2.
Saturation Magnetostriction of Single-Crystal YIG
Authors: Clark A. E. , DeSavage B. , Coleman W. , Callen E. R. , Callen H. B.
Published: April 2005

The magnetostriction of single-crystal yttrium iron garnet (YIG) has been measured from liquid nitrogen temperature to 450°K. The theory of magnetostriction of cubic crystals has also been extended to Néel ferrimagnets. The theoretical predictions of the temperature-dependent magnetostriction coefficients h1 and h2 are in excellent agreement with the measured values of −h1, which has a maximum (2.1×10−6) near room temperature, and of −h2, which falls monotonically with rising temperature (7.7×10−6 at 100°K and 4.2×10−6 at 300°K).
Spin-Wave Propagation and the Magnetoelastic Interaction in Yttrium Iron Garnet
Authors: Eshbach J. R.
Published: April 2005

Excitation of spin waves by the method of nonuniform internal dc magnetic fields in disk-shaped samples is demonstrated in two types of experiments. The first is a cw microwave absorption experiment in YIG disks. At high gain an absorption continuum is observed on the low field side of the magnetostatic mode spectrum of a disk magnetized perpendicular to its plane. This is shown to correspond to the expected absorption due to certain spin-wave modes in terms of the field values at which it occurs, its intensity and general shape. The second type of experiment permits observation of the propagation of microwave pulses via short wavelength spin waves and coupled magnetoelastic waves. The propagation time of the pulses is analyzed in terms of the group velocity of these waves and found to be in good agreement using known values of the exchange constant and velocities of elastic waves in YIG. The magnetoelastic coupling constant b2 in YIG is estimated from these experiments to be of the order of 107 ergs/cm3 or less.
Irradiation of Magnetic Materials with 1.5- and 4-MeV Protons
Authors: Sery R. S. , Gordon D. I.
Published: April 2005

Pure iron and 5% molybdenum Permalloy samples, 0.01 in. thick, were irradiated with 1.5- and 4-MeV protons at total incident integrated fluxes of 1016 and 1017 protons per cm2. The actual shapes used were a ring 1 31 6−in. o.d.×⅝-in. i.d. and a disk of ⅝-in. diameter. The ring was utilized for dc magnetic property measurements (before and after irradiation) while the disk was used for magnetic anisotropy torque measurements.

The remanence (Br) and maximum permeability (μm) of molybdenum Permalloy decreased by about 35%. This is of the same order of change produced by neutron irradiation of 1017 neutrons/cm2 in this material. However, measurements to date indicate that changes in coercive force and initial permeability due to proton irradiation are relatively small as compared with neutron irradiation effects. The decreases in Br and μm of the pure iron samples were of the order of 10 to 20% for irradiations of both ∼1016 and ∼1017 protons/cm2.

Both materials were essentially isotropic initially. Post irradiation torque measurements showed that the materials became slightly more isotropic. No changes were observed in saturation magnetization.

Heating of control samples to 250°C did not produce changes in magnetic properties, showing that temperature alone is not a factor in producing the permanent changes which occurred under irradiation. All irradiations were performed at temperatures below 250°C. The changes due to proton irradiation are thought to be due to proton-induced disordering.
Adsorption of Metals on Iron Particles in Mercury
Authors: Luborsky F. E. , Opie J. D.
Published: April 2005

Spherical iron particles in mercury were prepared by electrodeposition, and then aged to give particles with an average diameter of 180 Å. The addition of Pb, Cd, Ag, Cr, Ba, Cu, Bi, and In to the iron particles in mercury had no effect on the magnetic properties but As, Mn, Zn, Sn, Sb, Al, Ti, Mo, and Ni increased the coercive force. It was concluded that only those metals which could form intermetallic compounds with iron would increase the coercive force of iron particles in mercury. Quantitative measurements on Mn, Zn, Sn, and Sb showed that the coercive force increased, in the order given, without changing the magnetic moment. Thus, no compound formation actually occurred. The amount of these metals required to produce the complete magnetic effect corresponded to the adsorption of approximately a monolayer on the iron particle surfaces. The magnitude of the increase in coercive force was proportional to the atomic diameter of the adsorbed species as expected from the assumption that the increase in coercive force is due to the decrease in magnetostatic interaction caused by the absorption of metal atoms on the iron particle surfaces.
Magnetization Changes and Losses in Conducting Ferromagnetic Materials
Authors: Becker J. J.
Published: April 2005

This paper discusses magnetization changes and the losses associated with them in bulk metallic magnetic materials, whose behavior is determined by eddy currents. The various reversal mechanisms in these materials, the conditions under which each is operative, the losses associated with each, and the dependence of the behavior on various parameters are discussed.

The eddy-current-limited motion of an isolated domain wall is first considered. The behavior in increasingly large fields and the transition to a collapsing cylindrical or double planar wall in high fields are examined. The hysteresis loops and losses calculated for the isolated wall, the collapsing cylindrical wall, and the double planar wall are discussed for various conditions of excitation. The effects brought about in the low-frequency case by the presence of more than one wall are described, reviewing the results of theoretical calculations for multiple-wall configurations and the experimental results obtained with the superposed-high-frequency technique. The predictions of classical eddy-current theory and the ``eddy-current anomaly'' are discussed. The importance of selecting the correct model for the circumstances is illustrated by some data from the literature.
Magnetic Structure Investigations at the Nuclear Center
Authors: Ballestracci R. , Bertaut E. F. , Coing-Boyat J. , Delapalme A. , James W. , Lemaire R. , Pauthenet R. , Roult G.
Published: April 2005

The magnetic structure of the compounds UOS, β-CoSO4, YCo5, and HoCo5 is briefly described.

UOS is antiferromagnetic. The Néel temperature is Tn=55°K. The magnetic cell is doubled in the c direction with a ++−− sequence of U moments along c. The apparent spin is S∼1. The negative interaction corresponds to U-O-U links.

In β-CoSO4 (high-temperature modification, space group Pbnm), Co atoms are in 000, 00½, ½½½, ½½0. Here three different antiferromagnetic spin modes, mutually perpendicular, Ax(+−−+), Gy(+−+−), and Cz(++−−), in the Wollan-Koehler notation, are coupled. Direction cosines are 0.71, 0.50, and 0.50, respectively. The Co moment is about 3,84 μB at 4.2°K. A field-induced spin flip to the configuration Fx, Cy, Gz is predicted.

YCO5 is ferromagnetic at room temperature with a moment value of Co practically equal to that of metallic Co and moment direction along c, which is conserved down to 4.2°K.

In HoCo5 the moment of Ho is opposite to those of the Co atoms. When cooling from room to liquid helium temperature, the direction of easy magnetization changes from near c to a direction in the basal plane and the Ho moment increases from 4 to about 9 μB. The compensation temperature is 70°K.
Some Magnetic Properties of Gd Single Crystals
Authors: Graham C. D.
Published: April 2005

The magnetocrystalline anisotropy constants of Gd have been measured from 10° to 350°K. The behavior near the Curie temperature (about 300°K) is unusual: a fairly large, strongly field-dependent apparent anisotropy persists to temperatures at least 30° above the Curie temperature, and in the range 250° to 285°K this anisotropy decreases with increasing field above 4 kOe. Preliminary high-field (20 kOe) magnetization measurements indicate that there is no large difference in magnetization in different crystallographic directions in the vicinity of the Curie temperature. Low-field magnetization measurements from 77° to about 300°K are in qualitative agreement with curves calculated from the anisotropy constants, and do not support the suggestion of Belov and Pedko that Gd has a spiral spin structure in low fields above 210°K.
Magnetostriction and Anomalous Thermal Expansion of Single Crystals of Gadolinium
Authors: Bozorth R. M. , Wakiyama T.
Published: April 2005

Measurements have been made with strain gauges of the magnetostriction and thermal expansion of single crystals of gadolinium. The four magnetostriction constants of a hexagonal crystal have been determined from 4°K to above the Curie point, using fields to 30 kOe. The maximum in the forced magnetostriction, near the Curie point, is large and positive when the strain is measured parallel to the c axis, and small and negative perpendicular to this axis. Related to the forced magnetostriction is the anomaly in the thermal expansion coefficient; this shows a sharp maximum when the coefficient is measured parallel to a (as in nickel) and a minimum when measured parallel to c (as in iron), corresponding to positions, respectively, to the right and left of the maximum of the Bethe-Slater curve.
Structural and Magnetic Characteristics of Dysprosium-Yttrium Solid Solutions
Authors: Weinstein S. , Craig R. S. , Wallace W. E.
Published: April 2005

X-ray studies have shown that dysprosium and yttrium are miscible in all proportions in the solid state at room temperature. Vegard's law is approximately obeyed.

Thermomagnetic analyses were carried out between 4°K and room temperature and the field dependencies were measured at liquid He, liquid N2, and room temperature on alloys containing from 10 to 95 at.% Dy. Alloys containing less than 90 at.% Dy are paramagnetic at room temperature and antiferromagnetic at lower temperatures with no clear evidence of ferromagnetism down to liquid He temperatures. The Néel point (TN) decreases with decreasing Dy content, TN32 varying linearly with composition.

Alloys containing 90 and 95 at.% Dy are ferromagnetic at low temperatures. When the samples were cooled to 4°K in the absence of a field and the magnetization measured as the sample warmed up in a field, it was observed that the moment was initially low as if the sample were antiferromagnetic (or at least nonferromagnetic). With increasing temperature the moment rose sharply to a broad maximum at about 30°K. This was followed by the appearance of Curie and Néel points. When the sample was cooled in the presence of a field, the decreased moment at low temperatures was not observed.
Magnetic Characteristics of Laves Phases Containing Lanthanide Metals Combined with Nickel
Authors: Skrabek E. A. , Wallace W. E.
Published: April 2005

Studies have been made of the series of compounds represented by the formula ANi2, in which A is Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. These compounds are all isostructural, possessing the MgCu2 structure. Nine of the compounds exhibit magnetic ordering at temperatures ranging from 8°K (for PrNi2) to 90°K (for GdNi2). The Y, Ce, and Lu ramain paramagnetic down to liquid helium temperatures. YNi2 and LuNi2 exhibit Pauli paramagnetism from 4° to 300°K suggesting that nickel has a filled 3d shell and is not carrying a moment in these phases. CeNi2 likewise exhibits Pauli paramagnetism, which implies that Ce has been ionized to the quadripositive state.

The measured saturation moment extrapolated to 0°K is in good agreement with the value expected if nickel is nonmagnetic and the lanthanide component carries the moment of the free tripositive ion in the case of GdNi2 but is in poor agreement for the eight other compounds which order magnetically. For all except SmNi2, which appears to be a special case, the observed moment is less than that of the free ion, the discrepancy ranging from 78% for PrNi2 to 28% for HoNi2. The low moment is attributed to the quenching effect of the crystal field, but the possibility cannot be excluded that these are not simple ferromagnets.

The moment for SmNi2 is 6.3 μB, as compared with 0.71 μB for the ground state free tripositive ion (L-S coupling). The origin of the high moment for this compound is not understood. Its magnitude can be rationalized in terms of a change to L+S coupling.
Influence of Spin-Orbit Interaction on the Transport Processes in Ferromagnetic Nickel Alloys, in the Presence of a Degeneracy of the 3d Band
Authors: Berger L.
Published: April 2005

Assuming that two of the five branchs of the 3d band intersect, it is shown that singularities result in the transport properties when such an intersection happens to occur at the Fermi level. The ``ferromagnetic anisotropy of resistivity'' Δρ/ρ0 (often called magnetoresistance effect) is expected to have a strong maximum; using Born approximation for impurity scattering, and simple models of the 3d and 4s bands, a detailed computation provides an order of magnitude of 20% for the value of Δρ/ρ0 at the maximum. On the other hand, assuming the validity of current theories of the ``extraordinary Hall conductivity'' γHs due to Smit or to Karplus and Luttinger, γHs may be expected to change sign. This is precisely the behavior of Δρ/ρ0 and γHs observed by Smit in Co-Ni and Fe-Ni alloys, for an electron concentration equal to 27.7 electrons/atom.
Magnetic Moments and Electronic Properties of Manganese-Substituted Iron—Cobalt Alloys
Authors: Chen C. W.
Published: April 2005

The substitution of manganese in iron—cobalt alloys is shown to either decrease or increase the mean magnetic moments of the ternary alloys. The reversal of the magnetic effect of manganese occurs at the atom ratio Co:Fe=1:1. The increase of residual resistivity caused by manganese substitution also shows sensitive dependence upon the Co:Fe ratio and reaches a peak at Co:Fe=3:7. The latter ratio marks the termination of the extended simple dilution effect of manganese on the mean atomic moment. For alloys having Co:Fe ratios between 3:7 and 1:1, both the rate of decrease of the mean moment and the increase of residual resistivity diminish steadily with rise of the Co:Fe ratio. On the basis of a modified band model, the magnetic and electric properties of the manganese-substituted iron—cobalt alloys may be ascribed to the occupancy of the localized d states at the manganese atoms. When Co:Fe≥1:1, each manganese atom retains five electrons in the localized d shell in accord with Hund's rule. As the ratio decreases below unity, the localized d shell becomes first more than half-empty and eventually nonexistent.
Effect of Copper Plating on the Velocity of Propagation of a Normal Region in Niobium-25% Zirconium Wire
Authors: Stekly Z. J. J. , Hoag E.
Published: April 2005

The propagation velocity of the normal region in a 0.010-in.-diam niobium-25% zirconium wire plated with 0- to 0.001-in. thickness of copper was measured with varying currents flowing through the wire in the presence of magnetic field perpendicular to the wire. The normal region was artificially started with a heater wire wrapped around the specimen. The copper plating results in a lower resistivity in the normal state as well as a higher thermal conductivity along the wire. Experimental results indicate that for thin plating thicknesses the thermal conductivity predominates over the lower resistivity resulting in a considerably higher velocity of propagation in a plated wire.
Some Relations Between Superconducting and Magnetic Properties
Authors: De Gennes P. G. , Sarma G.
Published: April 2005

This paper discusses some effects of localized magnetic moments in a superconducting electron gas. (a) The two electrons with up and down spin of a Cooper pair are submitted to different potentials, and the stability of the pair is reduced. (b) Electrons interact via spin waves. Special attention is given to dilute magnetic alloys, antiferromagnetic systems, and to boundary effects between a ferromagnetic and a superconducting metal.
Compositional and Angular Dependence of the Magnetostriction of Thin Iron-Nickel Films
Authors: Mitchell E. N. , Lykken G. I. , Babcock G. D.
Published: April 2005

Theoretical consideration is given to the behavior of the anisotropy field of iron—nickel films ranging in composition from 65% Ni—35% Fe to 90% Ni—10% Fe as a function of applied external stresses and magnetic fields in various directions in the plane of the film. It is postulated that internal stresses in the substrate film system may account for observed discrepancies. An expression is derived which relates the magnetoelastic parameter (η) to the magnetostriction (λs) of the film. This parameter is measured as a function of composition and the predicted value of λs agrees within the limits of precision to that observed for bulk material. Assuming the films to be isotropic in the plane of the substrate, a relation between applied stress and change in the anisotropy field is developed and within limits experimentally verified. It is postulated that observed discrepancies are due to nonlinear anisotropic internal stresses and dispersion in the direction of the easy axis of the film.
Piezoresistance of Diffused Layers in Cubic Semiconductors
Authors: Kerr D. R. , Milnes A. G.
Published: April 2005

Piezoresistive characteristics of a diffused layer on the surface of a semiconductor having a cubic crystallographic structure are analyzed. The surface is assumed free of external forces, and the current component normal to the surface within the layer is assumed zero. The equations derived are useful in the design of diffused piezoresistive electromechanical transducers. The electric fields in the layer are related to the sheet current densities and the stresses by diffused piezoresistive coefficients, which are defined in integral form. These coefficients are functions of the fundamental piezoresistive coefficients, the crystal orientation, and the unstressed conductivity profile function in the layer, but are independent of the layer thickness. The coefficient of major interest is numerically evaluated as a function of surface impurity concentration for p-type silicon and n-type germanium-diffused layers with Gaussian and complementary error function impurity distributions. Measurements on diffused samples are in agreement with the analysis. The magnitude of a nonlinearity in layer piezoresistance arising from the variations of the bulk coefficients with doping is estimated.
A Complete E, P, V, T, S Thermodynamic Description of Metals Based on the P, u Mirror-Image Approximation
Authors: Enig Julius W.
Published: April 2005

The well-known practice of using the mirror-image, in the P, u plane, of the shock Hugoniot curve about a vertical line through the shocked state PH, uH is shown to give a complete thermodynamic description of metals when the U (shock velocity) vs uH relationship and α≡V-1(δV /δT)P≈0 are known. Use of the experimental relationship U = c0+auH (a and c0 constants) and α = constant, leads to a thermodynamic description which results in the metal appearing less compressible than if described by the Mie—Grüneisen equation of state. Furthermore, the existance of an anomalous behavior of cp in the low pressure neighborhood (<10 to <50 kbar depending on the metal) of the initial state rules out the simultaneous existence of a Hugoniot satisfying the linear U vs uH relationship, of isentropes satisfying the mirror-image assumption, and of a constant value of α in this neighborhood. Thermodynamic functions for 16 metals are calculated up to 2 Mbars and compared with the results obtained from the Mie—Grüneisen equation of state.
Surface Diffusion from a Point Source
Authors: Shewmon Paul G.
Published: April 2005

This paper develops the equations needed to determine the surface diffusion coefficient (Ds) when a point source is used and solute is drained off from the high diffusivity surface layer into the bulk. The assumptions used are essentially those used by Fisher for his analysis of grain boundary enhanced diffusion, and the results are equally simple to use. The conditions under which Ds can be most easily and accurately determined are discussed.
Magnetic Field Effects on an Abnormal Truncated Glow Discharge and Their Relation to Sputtered Thin-Film Growth
Authors: Kay Eric
Published: April 2005

Superposition of a radially symmetric magnetic quadrupole field onto an abnormal glow discharge operating at E/P of 105 produces an additional ionization region in the negative glow which is not observed in the absence of a magnetic field and which increases the ion current density at the cathode by more than an order of magnitude. Preliminary Langmuir probe measurements show the electric field gradient in this region to be small and an average electron energy of only 0.8 eV. Data are given to show how sputtering ratio measurements in such a system can be correlated to secondary electron emission at the cathode and charge transfer in the Crooks dark space. Ion current density profile measurements across the cathode as well as corresponding cathode erosion and anode deposition profiles are given.
Elastic Constants of Thallium Single Crystals in the Temperature Range 4.2°–300°K
Authors: Ferris R. W. , Shepard M. L. , Smith J. F.
Published: April 2005

The five independent elastic constants of single crystals of the hexagonal allotrope of thallium have been determined by the ultrasonic pulse-echo technique over the temperature range, 4.2°–300°K. The values at 300°K in units of 1011 dyn/cm2 are C11=4.080, C33=5.280, C44=0.726, C12=3.54, and C13=2.9. The compressibility derived from these elastic constants is in good agreement with the compressibility obtained by Bridgman from hydrostatic measurements on polycrystalline samples.
Secondary Electron Emission of Pyrolytic Graphite Cleaved in a High Vacuum
Authors: Whetten N. Rey
Published: April 2005

Pyrolytic graphite was cleaved in a high vacuum to obtain clean surfaces, and the secondary electron emission properties of these surfaces were determined. Pyrolytic graphite has a maximum secondary emission yield of 1.0 at 300-eV primary electron energy for electrons incident normal to the basal plane. The most probable energy of the emitted secondaries is 2 eV, with one-half of the secondaries having energy in excess of 8 eV. A maximum secondary emission yield of 0.75 at 350-eV primary energy was measured for normal incident electrons on a face that was perpendicular to the basal plane. The backscattered fraction for pyrolytic graphite was found to be 0.05. No differences were observed in the secondary electron emission properties of single-crystalline pyrolytic graphite and pyrolytic graphite that was less well ordered.
Some Causes of Resonant Frequency Shifts in Atomic Beam Machines. I. Shifts Due to Other Frequencies of Excitation
Authors: Shirley Jon H.
Published: April 2005

The quantum theory of an atomic beam machine is set up in matrix form. A new method is then used to derive the Bloch-Siegert shift in the resonance. The results are extended to the case of Ramsey-type excitation. Finally the Bloch-Siegert shift is computed for the present atomic beam frequency standards and found to be well below the accuracy of measurement.
Domain Patterns in Electrodeposited Nickel-Iron Thin Films
Authors: Kainuma Seizo , Tsuya Noboru
Published: April 2005

Observations of Bitter patterns were carried out for two varieties of Ni–Fe alloy thin films electrodeposited without magnetic field onto mechanically polished copper substrates. These two sorts of films were composed of 80Ni-20Fe ``Film 1'' and 82.5Ni-17.5Fe ``Film 2'' and were Fe-rich and Ni-rich from the composition of 81.5Ni-18.5Fe with minimum coercive force. The behavior of magnetic domains was examined during various magnetic processes and under externally applied stress. It was found that: (i), in ``Film 1,'' the easy axis is parallel to the scratches on the substrates and the domain walls fall into those scratches; and (ii), in ``Film 2,'' an averaged easy direction is induced perpendicular to the scratches in several films, whereas in the other films it was not well-established. These results are well explained, being consistent with the hysteresis characteristics, by assuming that magnetostriction is positive in ``Film 1'' and negative in ``Film 2'' and that magnetoelastic and shape anisotropies both are induced, accompanying the scratches on the surface of the substrates.
One-Carrier Space-Charge-Limited Current in Solids
Authors: Lindmayer J. , Reynolds J. , Wrigley C.
Published: April 2005

The one-carrier, trap-free space-charge-limited current is calculated and the general solution is given in the form of a computed, normalized voltage-current curve. Both diffusion and drift currents are considered. The result is then compared with the widely used J ∝ V2 expression and it is shown that this relation is valid for voltages greater than 100 kT/q. The contradictions arising in the J ∝ V2 derivation are clarified. Finally, the carrier transit time through the space-charge-limited region is given.
Ion Bombardment of Silicon
Authors: Primak W. , Dayal Y. , Edwards E.
Published: April 2005

When silicon plates were bombarded with protons of energies about 100 kV, the infrared absorption spectrum above 1.1 μ showed chromatic fringes corresponding approximately to the range of the protons. The fringes did not begin to disappear on annealing until the plates were heated to over 1100°C. The effect appears to be caused by a reflecting layer involving trapped hydrogen. After long irradiation, small flatbottomed pits were found of about the depth of the range.

The effect could also be produced with helium ions on silicon. No effect was found with germanium.
Resonances of the Fabry-Perot Laser
Authors: Barone S. R.
Published: April 2005

The optical mode structure of a Fabry—Perot interferometer-resonator composed of two infinite strip mirrors is investigated from the point of view of the general theory of nonspectral resonances. It is shown that the classical description of this configuration is inadequate to describe its response to highly monochromatic laser radiation and must be supplemented by a discussion of the transverse resonance behavior. This introduces a fine structure to the classical Fabry—Perot rings and implies a discrete resonance behavior for the Fabry—Perot interferometer. In analogy to the characterization of quantum-mechanical virtual levels by wavefunctions and complex energies it is convenient to characterize the discrete resonances of a Fabry—Perot by mode functions and complex resonant frequencies. On the basis of a reformulation and asymptotic expansion of a previously given stationary expression, it is shown that in the high-frequency limit, the open sides of the structure can be replaced by an effective impedance boundary condition. The solution of an elementary resonance problem then yields analytic approximations for the mode shapes, characteristic oscillation frequencies, and modal lifetimes. In the common domain of validity these results are in excellent agreement with previous numerical work on this problem.
Hugoniot Equation of State of Pyrolytic Graphite to 300 kbars
Authors: Doran D. G.
Published: April 2005

The Hugoniot equation of state of pyrolytic graphite of initial density 2.20 g/cm3 has been determined to 300 kb for the ``c'' direction. Various explosive techniques for producing the desired pressures, and the optical techniques employed in measuring shock and free-surface velocities are briefly described. It is found that shock and particle velocity are not linearly related below 70 kb. Above 100 kb, the material is less dense than is powdered natural graphite, as determined by Alder and Christian. The agreement with static compressibility data is satisfactory.
Thermally Activated Dislocation Kink Motion in Silicon
Authors: Southgate P. D. , Attard A. E.
Published: April 2005

The internal friction of deformed silicon crystals has been measured between 3 and 60 kc/sec, up to 1100°C. The component of internal friction due to dislocations becomes appreciable at 500°C, and rises steadily above this temperature. An Arrhenius plot yields an activation energy of 1.61±0.05 eV for all specimens measured, while the magnitude of the internal friction at any given temperature is approximately proportional to dislocation density and inversely proportional to the frequency. An interpretation of the results is discussed in terms of the kinked-dislocation theories of Brailsford and of Seeger and Schiller. Suitable augmentation of these theories is shown to bring them into a unified form, which is compatible with the Koehler-Granato-Lücke extensible string formulation, at least in the temperature range where thermal kink pair generation is negligible. Reasonable assumptions of kink mobility and density give agreement with the theory; the measured activation energy is then that for kink motion. Comparison with results of Chaudhuri et al. shows that this is less than that for gross dislocation movement.
Triple Correlator of Photoelectric Fluctuations as a Spectroscopic Tool
Authors: Gamo Hideya
Published: April 2005

A triple correlator of fluctuating photocurrents is shown to be able to analyze asymmetrical spectrum profiles of light beams, such as laser beams, without the use of an additional light source. The resolving time of photodetectors, multipliers, and electronic delay lines involved must be shorter than the coherence time of the light beam to be analyzed. The method cannot determine the mean frequency of an incident beam and cannot distinguish between a spectrum profile and its mirror image around the mean frequency.
Optical Maser Characteristics of Rare-Earth Ions in Crystals
Authors: Johnson L. F.
Published: April 2005

Several divalent and trivalent rare-earth ions incorporated in various host crystals have been found to exhibit stimulated emission in the near infrared. A report is presented describing some of the basic characteristics of these materials: absorption and fluorescence spectra, energy level diagrams, optical maser wavelengths and operating temperatures, and thresholds for stimulated emission. Recent observations on the CaWO4:Nd3+ optical maser in continuous operation are also described.
Reflection and Refraction of Mechanical Waves at Solid-Liquid Boundaries
Authors: Mayer Walter G.
Published: April 2005

The energy ratios of reflected and refracted waves to the incident wave at ten liquid-solid boundaries are calculated as a function of the angle of incidence. The influence of the wave velocities in the media and their density on the shape of the curves is discussed.