bluuebunny/crossref_metadata_2025 huggingface dataset:
Some static and dynamic properties of cylindrically symmetric bubbles
Authors: Kos B. , Sukiennicki A.
Published: February 2003

Magnetization distribution in two-dimensional walls of cylindrically symmetric bubbles is calculated numerically. Fundamental static properties, such as the total energy, the radius, the wall width and the collapse instability condition for such bubbles are obtained and discussed. Some dynamic properties like the velocity versus momentum relationships for considered bubbles are also calculated. The results may be used for explanation of various experimental effects.
A new measuring method of magnetostrictive vibration
Authors: Kakuno K. , Gondó Y.
Published: February 2003

A new method for measuring magnetostrictive vibrational displacements has been developed by utilizing a laser interferometric technique with sensitivity enough to detect a vibrational displacement of 10 Å. The most striking merit of this method is that a non-contact and reaction free measuring is essentially permitted. The reliability of this interferometric method is checked by measuring vibrational displacements of a cylindrical nickel rod specimen by means of both the present method and the conventional strain gauge method simultaneously. It is found that the agreement between the two experimental results obtained on the basis of these methods is very good. Therefore, it is concluded that the present interferometric method is quite reliable. The magnitude and the sign of the magnetostrictive vibrational displacements of the cylindrical rod specimens of a single crystal nickel and a polycrystal Ni60-Fe40 alloy are measured by means of the present interferometric method. Satisfactory results are obtained.
A model for a two sublattice system with high competing single ion anisotropies
Authors: Rinaldi S. , Pareti L.
Published: February 2003

In some Rare Earth-Transition Metals compounds the anisotropy shows a complex behaviour: easy direction of magnetization out of the crystallographic axis, large high order anisotropy constants and jumps in the magnetization curves were measured. We observed that these effects were present in systems where the anisotropies of the various sublattices were strong and opposite (axial vs. planar) and where the exchange was not strong enough to completely dominate. We developed a quantitative model taking into account the competition between the exchange and the difference in the anisotropies allowing for possible canting between the sublattice magnetizations. We found that a canting angle is indeed possible although it is small and dependent on the orientation of the resultant magnetization. However the possibility of deviating from the collinear order results in an energy relaxation that greatly distorts the shape of the anisotropy energy surface. Consequently the anisotropy of the resulting system cannot be described by the sum of the anisotropy constants of the individual sublattices: strong corrections and higher order terms must be taken into consideration. These corrections, calculated from realistic values of the parameters, turn out to have the right sign and magnitude so as to justify the observed phenomena.
Magnetostriction and anisotropy of amorphous Gd-Co r.f. sputtered thin films
Authors: Twarowski K. , Lachowicz H. K.
Published: February 2003

The measurements of magnetostriction and anisotropy of r.f. sputtered amorphous Gd1−xCox thin films are reported. Both were measured in the range of composition x=0.667–0.835 using cantilever-capacitance method. The perpendicular anisotropy Ku and saturation magnetostriction λs reach extremal values in the vicinity of the compensation composition (for x=0.77), although Ku shows a minimum of ∼1×105erg/cm3, whereas (3/2) λs shows a maximum of ∼47×10−6. The experimental results are analysed within the frame of pair ordering model. A mechanism explaining the compositional dependence of magnetostriction is proposed.
Generation and attenuation of phonons at ferromagnetic resonance in thick Ni films
Authors: Privorotskii I. A. , Devine R. A. B. , Alexandrakis G. C.
Published: February 2003

The generation and attenuation of phonons at ferromagnetic resonance has been studied both theoretically and experimentally. We have observed for the first time the effect of resonant reabsorption of phonons propagating through thick Ni films. The predictions of the theory are in very good agreement with experiment.
EPR study of cold-worked dilute gold-erbium alloys
Authors: Raizman A. , Suss J. T. , Seidman D. N. , Shaltiel D. , Zevin V. , Orbach R.
Published: February 2003

The results of an electron paramagnetic resonance (EPR) study of the effects of cold-working (rolling and polishing) on the EPR spectrum of Er in Au are reported. Pellets of dilute alloys of Au doped with Er were prepared in an arc furnace. From the pellets, samples were made by rolling at room temperature. The resonance experiments were carried out at X-band and at temperatures between 1.65 and 4.2 K. Heating of the rolled samples reduced the EPR linewidth and intensity and increased the asymmetry parameter (the A/B ratio). Gradual deformation by successive rolling resulted in almost complete recovery of the linewidth and A/B ratio to values observed before heating. No appreciable variations were detected in the g-factor, hyperfine structure constant or the Korringa relaxation rate. Results are interpreted in terms of segregation of Er ions to subgrain boundaries. The EPR of magnetic impurities in metals appears to be a promising technique for the study of interactions between the magnetic impurities and the defects produced by cold-working.
Nuclear magnetic resonance in one-dimensional planar magnets
Authors: Huber D. L. , Ghosh K.
Published: February 2003

We analyze low-temperature nuclear magnetic resonance in quasi-one dimensional planar magnets. For configurations in which the static field is perpendicular to the hard axis we calculate the nuclear relaxation times T1 and T2 using linearized magnon theory. The dominant T2 process is associated with the raman scattering of the long wavelength magnons. Longitudinal relaxation is brought about by a three-magnon process. We also calculate the temperature and field dependence of the magnetization which is then matched with experimental data to determine the region of applicability of the theory in the field-temperature plane. Our calculated values of T1 and T2 are compared with data obtained from CsNiF3 and with the corresponding zero-field predictions. Reasonable agreement is obtained between experiment and theory.
Effects of nontrigonal crystal field on spectroscopic properties of Fe2+ ion in YIG:Si(Ge)
Authors: Rudowicz Cz.
Published: February 2003

The present work reports the theoretical considerations of the effects of nontrigonal crystal field on the electronic structure of ferrous ions induced by tetravalent dopants in YIG. It is found that a spin Hamiltonian can well acount for the spectroscopic properties of the ground orbital singlet of the ferrous ion in YIG. A numerical method is worked out to calculate the parameters involved in the theory, namely, the three second-order and the five fourth-order zero-field parameters, and the four components of the Zeeman g-tensor. A wide range of the microscopic parameters is considered and some representative results are given. The properties of the nearby (I) and far (II) ferrous centers can now be well explained. The centers II are shown to be more anisotropic than the centers I. The dominant second-order axial parameter is found to be positive and of the value of several inverse cm.
Domain structure induced by a strong magnetic field in monclinic antiferromagnet NiWO4
Authors: Eremenko V. V. , Dudko K. L. , Gapon N. V.
Published: February 2003

A strong external magnetic field, Hc=176 kOe, applied along the ordering axis of antiferromagnetic NiWO4 produces spin flopping. This orientational transition results in sharp changes both in longitudinal and transverse components of the magnetization vector. It is found that for certain external magnetic field orientations, spin flopping in NiWO4 is a first order phase transition. The measurement results for magnetic properties suggest that an intermediate state appears in this field region, where the sample laminates into magnetic domains. The domain layer directions make an angle with the vector of the inducing magnetic field, which can be varied by minor changes in the external field direction.
Abstract: The magnetization of ancient pottery and its potential for dating in archaeology
Authors: Walton D.
Published: February 2003

When pottery is fired and subsequently cooled in the earth’s magnetic field it acquires a moment which for fields ≲ 2–3 Oe is proportional to the intensity. It is possible to deduce this intensity from the magnetization. If the variation in intensity is sufficiently rapid it should be possible to use the information to refine a date for a piece of pottery. Values for the geomagnetic intensity in Athens between 2000 B.C. and A.D. 400 have been obtained from sherds excavated from wells and grave sites in the ancient Agora.1 These data reveal fluctuations in intensity with values as high as twice the present day field in 600 B.C. and 450 B.C. The rate of change is sufficient to suggest the possibility of dating a piece of pottery to ± 30 years in some periods. Comparison of these data with that obtained by others for Central America and Japan indicate that the features are geophysical in origin. Thus, they may to some extent be used to predict the field at other locations on the earth’s surface. 1 D. Walton, Nature 277, 643 (1979).
Abstract: Magnetic and transport properties of metglas Fe40Ni38Mo4B18
Authors: Majumdar A. K. , Nigam A. K.
Published: February 2003

Systematic studies of the magnetic susceptibility, the ferromagnetic anisotropy of resistivity (FAR) and the Hall effect are lacking in the amorphous ferromagnet Fe40Ni38Mo4B18 (Metglas 2826 MB). Lowfield susceptibility has been measured between 300 K to 1000 K in the amorphous, thermally cycled and crystallized states. The kink-point method yields Tc=589 K while −dμ/dT vs T plot gives Tc=593 K in the amorphous state. Differential thermal analysis shows no crystallization below 720 K. A thermal cycling up to 1000 K at a heating rate of 3 K/min produces two crystalline magnetic phases with Tc= (760±10) K and (545±5) K. Samples annealed at 1000 K for 4 hrs also show the same two phases, only the transitions are somewhat sharper. Longitudinal and transverse magnetoresistivity curves are very similar to that of the crystalline ferromagnets. The FAR is very small and positive with a typical value of 0.1%. The average negative slope at high fields, due to less electron–magnon scattering, changes from −1.1×10−8 gauss−1 to −0.55×10−3 gauss−from 300 K to 77 K. The values of FAR, the high-field slopes, the electrical resistivity, the Hall constants and the Hall conductivity will be compared with those of other metal glasses and their crystalline counterparts. The negative transverse magnetoresistance δR/Ro=−4.5×10−4 is found to be roughly proportional to β2 where β = the tangent of the Hall angle = 2.2×10−2. This result, together with the existing data for other metal glasses will be interpreted in terms of the existence of one easy axis of magnetization associated with the anisotropy energy and the decrease of ρ with the removal of domain walls.
Magnetic ordering temperature, hyperfine field distribution and electrical resistivity of amorphous (FexMn1−x)75P16B6Al3
Authors: Chien C. L. , Hsu J. H. , Stokes J. P. , Bloch A. N. , Chen H. S.
Published: February 2003

Mössbauer studies of amorphous (FexMn1−x)75P16B6Al3 show a rapid drop in the magnetic ordering temperature and the development of a second, low-field peak in the hyperfine field distribution P(H) as x is decreased from unity. The magnetic ordering does not affect the electrical resistivity, but the changes in P(H) are correlated with the appearance of a broad, high-temperature resistance minimum. A second, anomalous resistance minimum, different from the first, appears at a low temperature which is nearly independent of x.
Magnetic and transport properties of rare-earth Au and Cu amorphous alloys
Authors: McGuire T. R. , Gambino R. J.
Published: February 2003

Magnetic moment, Hall effect and resistivity of amorphous film alloys of rare earth metals with 0.4 to 0.6 atomic fraction of Au or Cu have been studied. Alloys with Nd, Gd, Dy, Tb and Ho are ferromagnetic at 4.2 °K. All but Gd have Curie temperatures below 20 °K; for Gd-Au and Gd-Cu Tc is approximately 100 °K. In addition the Gd alloys have almost full magnetization (4πM) while the remaining ferromagnetic rare earth alloys have values of 4πM only one-third to one-half of the expected saturation. Resistivities of the alloys range from 80 μΩ cm for Pr-Cu to 230 μΩ cm for Nd-Au and in general they have small negative temperature coefficients. The spontaneous Hall effect is positive for all the light rare earths with Au including Eu and negative for Gd and the remaining heavy rare earths. In the RE-Cu series the same is true except Dy through Tm have positive Hall values. The Hall Coefficient Rs for the heavy rare earths is largest for Gd where .Rs?−0.5×10−9Ω cm/G. The sign of the Hall effect in the Au series can be attributed in part to conduction electron interactions with the spin of the rare earth atoms since the spins point in opposite directions for the light and heavy rare earths. In addition, for the heavy rare earth-Au series the tangent of the Hall angle, ρH/ρ, is proportional to the paramagnetic ϑ value of the alloy. The positive shift of ρH/ρ for the RE-Cu series may have its origin in polarization of Cu by the RE moments.
Compositional short-range-order effects in the Hall resistivity of amorphous Fe27Ni53P14B6
Authors: Malmhäll R. , Bäckström G. , Rao K. V. , Egami T.
Published: February 2003

Hall resistivity ( ρH) studies confirm that the Curie temperature (Tc) can be varied reproducibly between 374 K and 368 K by suitably annealing the alloy at 250 °C and 300 °C respectively. This is explained as being due to changes in compositional short-range-order. The calculated magnetic susceptibility, obtained from the temperature dependence of ρH, shows a strong fluctuation contribution described by (T−Tc)−γ, with γ=1.54±0.04 in both cases. A significant contribution to the temperature dependence of the ohmic resistivity, which is also uneffected by the annealing conditions, is found to be of magnetic origin.
Metalloid effects in the low temperature specific heat of transition metal metallic glasses
Authors: Krause J. K. , Long T. C. , Onn David G. , Luborsky F. E.
Published: February 2003

The specific heat (Cp) between 0.8 K and 40 K for the metallic glasses Fe80B20, Fe40Ni40B20 and Fe82B15Si3 has been measured to ascertain the effects of metalloid composition. We find significant differences in both the lattice and the electronic contribution when compared to similar metallic glasses containing phosphorous, such as FexNi80−xP14B6.
Spin wave spectra of non-magnetostrictive amorphous alloy films
Authors: Suran G. , Gambino R. J.
Published: February 2003

The magnetic properties of a series of amorphous sputter deposited films were studied having the composition (Co1−xFexNiy)80 (Si1−zBz)20 with x?0.1, y?0.4, z?0.6. The composition was chosen in order to obtain close to zero magnetostriction (λs?0). Hysteresis measurements confirmed that these films are soft ferromagnetics. F.M.R. performed on films in the thickness range 0.1–0.6 μm shows well defined standing spin wave spectra corresponding to highly uniform samples: Modes with n?2 follow a quadratic dispersion law with an excellent precision, the intensity of various spin wave modes decrease as 1/n2<In<1/n4 and the corresponding linewidth ΔHn increases smoothly with n. A simple model is used to explain the origin of the pinning which is attributed to slight fluctuations of Ms or Hi of the order of 40–100 Oe. The value of D as deduced from S.S.W. spectra is in excellent agreement with that deduced from static measurements of Ms=f(T).
Abstract: Transport properties of amorphous metals
Authors: Harris R. , Muir W. B. , Strom-Olsen J. O. , Zuckermann M. J. , Cochrane R. W.
Published: February 2003

It is convenient to divide amorphous metallic alloys into two general categories :metal-metalloid systems, such as Co-P and the ’’metglasses’’, and metal-metal systems such as Tb-Ag or Y-Ni. All these materials display such interesting transport properties as negative temperature coefficients and/or low temperature minima in the electrical resistivity. In this paper we review existing data and analyze them using both magnetic and non-magnetic models. Data for the thermo-power of metal-metalloid alloys will also be presented. In the second part of the paper, we will discuss specific metal-metal alloys. particular attention will be given to Yttrium-based alloys, Cu-Zr alloys, rare-earth transition metal and rare-earth noble metal alloys.
Mössbauer effect investigations of the electronic and magnetic properties of rare earth metal and intermetallic hydrides
Authors: Dunlap B. D. , Shenoy G. K. , Friedt J. M. , Viccaro P. J. , Niarchos D. , Kierstead H. , Aldred A. T. , Westlake D. G.
Published: February 2003

Mössbauer spectroscopy has been used in a number of investigations of elemental rare earth (RE) metal and RE–transition metal intermetallic hydrides. Analysis of hyperfine parameters has established the crystalline electric field (CEF) ground state for Dy3+ in DyH2 and for Er3+ in ErH2 and YH2. In all cases the results are compatible with the presence of negatively charged hydrogen atoms. Long range magnetic ordering is observed in the RE-H2 compounds. In DyH2, short-range magnetic ordering is seen at temperatures up to twice the long-range transition temperature. This arises from the changes in CEF symmetry due to the presence of a few H atoms which are not in regular tetrahedral sites. These effects are much more pronounced in slightly non-stoichiometric compounds and can result in dramatic changes in the magnetic ordering temperature. As an example of an intermetallic hydride, we have studied the cubic Laves phase RE-iron compounds. These form several stable hydride phases RE-Fe2Hx, with the maximum x being in excess of 4. The magnetic transition temperatures decrease to roughly half their original values for x=3.5, and the RE-Fe exchange interaction is weakened. For x=4, a sharp reduction in both the Fe magnetic moment and the magnetic ordering temperature occurs.
Magnetic monitoring of SmCo5 thin film hydriding kinetics
Authors: Larsen J. W. , Livesay B. R.
Published: February 2003

Sufficiently thin films of hydrogen storage alloys are found to not experience decrepitation upon hydriding and thus provide a well defined metal-gas interface for the study of hydriding surface kinetics. An in situ magnetic torque method was developed to monitor hydriding-dehydriding rates. The films produced by r.f. sputtering in argon were hydrided using 490 psia hydrogen gas and dehydrided against vacuum. The 1080Å film exhibited rate behavior described by the Equation, F(t) =1 −exp [−(t/τ)1/2]. The rate constant, τ, was 120 sec for hydriding and 574 sec for dehydriding. The rate behavior of a 1420Å film is best described by F(t) =1 −exp [−(t/τ)2], with τ=685 sec for hydriding and 214 sec for dehydriding. Partial pressures of 1, 2, and 4% nitrogen gas were added and the reaction rates measured again. The rate constants were about 1200 sec, 2450 sec, and 5900 sec, respectively, for 1, 2, and 4% partial pressures of N2. The rates were almost identical for both hydriding and dehydriding. The reaction rates did not fully recover after the nitrogen was removed. This indicates a blockage, which is not completely reversible, of the hydrogen entry points.
Eddy current losses in magnetic sheet with simple bar-like 180° domain structures
Authors: Charap S. H.
Published: February 2003

The eddy current losses in thin magnetic sheets have finite width (W), thickness (d) and simple bar-like domain structures are calculated numerically assuming sinusoidal time variation of flux and uniform domain wall speeds. The Pry and Bean values for the ratio of calculated eddy current loss (Pe) to its classical value (Pc) are attained for fixed domain width (2L) in the limit W→∞. For a fixed number of domains (N) it is found that Pe/Pc has essentially the Pry and Bean value for 2L/d≳2 if N is odd (half-size end domains). With decreasing domain width, Pe/Pc decreases monotonically and, for fixed N (odd or even), tends to zero as 2L/d→0.
The Clauser-Blume model for the Mössbauer line shape with non-stationary relaxation effects
Authors: Banerjee Salil
Published: February 2003

The Clauser-Blume model for the Mössbauer line shape with stationary relaxation processes has been extended to include the effects of non-stationary relaxation processes. In the Clauser-Blume model, the emitting nucleus along with the hyperfine-coupled electronic system was assumed to have a stationary Hamiltonian. But there are cases in which the electronic system is not in equilibrium and decays with a life-time comparable to the life-time of the Mössbauer nucleus. Existence of these non-stationary processes along with the stationary Clauser-Blume relaxation makes the computation of the line shape somewhat more difficult. We present such a result for a simple model of the non-stationary effect in which the electronic decay just causes a change in the monopole interaction between the nucleus and the electronic system and results in a simple isomeric shift in frequency. The final result is a sum of three terms, each term being a product of two resonance denominators. The complicated expression reduces to previously known results in suitable limits. However, in this case when both kinds of relaxation are present, we expect interesting mixing effects of the two in the line shape. Possibilities of finding experimental systems describable by the model presented here are discussed.
Saturation magnetostriction and its annealing behavior of Fe100−xBx and Co100−xBx amorphous alloys
Authors: Narita K. , Yamasaki J. , Fukunaga H.
Published: February 2003

Boron content dependences of saturation magnetostriction λs at room temperature in as-quenched and annealed Fe100−xBx (15?x?25) and Co100−xBx (19?x?24) amorphous alloys were measured. The value of λs in Fe-B alloys peaks at x=20, while λs in Co-B alloys decreases with increasing boron content. For two series of alloys, nearly quadratic relations between magnetostriction and saturation magnetization σs were found. After 1 hour annealing at 250° C, both λs and σs in Fe-B and Co-B alloys increased. The increase in λs of Fe-B alloys was within 8%, and was larger than that of Co-B alloys. For annealed Fe-B and Co-B alloys, quadratic relations were also observed, which suggests that the increase in magnetostriction arises from the increase in magnetization.
Effect of annealing on the Curie temperature of amorphous alloys
Authors: Chen Y.-N. , Egami T.
Published: February 2003

Effect of annealing on the Curie temperature of amorphous Fe-Ni base alloys is studied. Experimental results on three alloys with different metalloid compositions and the analysis of the previously published data indicate that the changes in the Curie temperature are caused primarily by the compositional short range ordering between Ni and Fe, and the kinetics of the change is dependent on the topological short range order in the alloy.
Measurement of magnetic potential distribution and wall velocity in amorphous films
Authors: Onishi K. , Tonomura H. , Sakurai Y.
Published: February 2003

Rare-earth transition metal amorphous thin films which have uniaxial magnetic anisotropy perpendicular to the film plane were prepared by rf-sputtering or thermal evaporation. It was found that these amorphous magnetic films have a large extraordinary Hall effect. We measured the surface potential distribution for various domain patterns in the films. The correlation between the surface potential distribution and the shape of domain pattern was observed. We also measured the relation between the Hall voltage and the position of straight domain wall. From this measurement, we confirmed that the geometry of the element (the ratio of the length L to the width W) affects the positional dependence of Hall voltage, and the sensitive region in the film with respect to the Hall electrodes. We measured the domain wall velocity in Gd-Co amorphous films. Indicial response of the straight domain wall in these films to the pulse magnetic field was obtained.
Magnetic interactions between localized spins in an amorphous carbon char
Authors: Sarachik M. P. , Smith F. W.
Published: February 2003

The coupling between localized spins in an amorphous carbon char, determined from measurements of magnetic susceptibility and magnetization at low temperatures, has been observed to increase rapidly as a function of heat treatment temperature (HTT). For a carbon char formed from anthracence at 450 C, the strength of the coupling is observed to increase by an order of magnitude while the concentration of localized spins decreases by a factor of five as the sample is carbonized by heat treatments between 610 and 900 C. The decrease in spin density with increasing HTT reflects the reduction in the number of carbon atoms with unsatisfied valences, while the increased coupling between spins signals a growing density of delocalized electrons in the materials.
Abstract: Soft magnetic properties and magnetostriction of sputter-deposited bulk amorphous alloys
Authors: Fujimori H. , Kazama N. S.
Published: February 2003

Bulk amorphous ferromagnets, interesting in soft magnets or magnetostrictive materials, were produced by a high rate sputtering technique based on dc-triode method. The deposition was done onto a water cooled copper substrate. About 0.5−1 mm thick disks or rings (10–40 mm in diameter) in the amorphous state were obtained for Fe or Co rich alloys including metalloids and rare earth elements. All the alloy deposits were removed from the substrate, and then measurements were made of the B–H hysteresis loop and magnetostriction at room temperature and the saturation magnetization in the wide temperature range. (1) In the CO rich Co–Fe–Si–B alloys, the B–H loops show low remanence and large Barkhausen effect, representing coercivity ranging from 0.1 to 0.3 Oe. By annealing above the Curie point, the Barkhausen effect disappears and the coercivity decreases markedly. Particularly in the nearly zero magnetostrictive alloys very low values near 0.002 Oe can be obtained, Co67Fe5Si10B18 is typical. (2) Fe rich Fe–C and Fe–B alloys near 20 at.% of C and B exhibit large saturation magnetostriction of about 32×10−6. Distinguishably, the magnetostriction can be changed by adding only a few percent of rare earth elements; the magnetostriction constant of (Fe1–XRX)83B17, where R is Sm, Tb and Dy, increases up to about 40×10−6 for x=0.05 of Tb or Dy, while it decreases down to about 20×10−6 for x=0.05 of Sm. In the Tb case, longitudinal magnetostriction is as large as 60×10−6 but transverse value is vanishingly small. This suggests that spontaneous magnetization is declined from the in-plane of the disk deposits. Mean magnetic moment per Fe+R in these alloys can be explained by assuming the antiparallel coupling of the atomic moments of Fe and R.
Polarized neutron study of the itinerant electron metamagnetism in ThCo5
Authors: Givord D. , Laforest J. , Lemaire R.
Published: February 2003

The peculiar magnetic properties of the ferromagnetic compound ThCo5 have been studied by means of polarized neutrons. The first order magnetic transition, induced below 150 K by an applied field corresponds to an increase of the magnetization of the two Co sites (2c, 3g). The thermal variations of the spontaneous magnetizations and the superimposed susceptibilities exhibit a maximum at about 170 K. But, adding to the applied field the exchange field due to interactions between the two sites, it appears that only Co atoms of the 3g site exhibit a maximum of the susceptibility, which is reminiscent of the one observed in the Pauli paramagnet YCo2. The results show the character of itinerant electron metamagnetism of the 3g site. Such a property is often observed in compounds where the 3d band is hybridized with less localized d electrons.
Magnetic moment distribution in Ni-Pt alloys
Authors: Parra R. E. , Cable J. W.
Published: February 2003

We have measured the magnetic diffuse scattering of polarized and unpolarized neutrons from ferromagnetic Ni-Pt alloys with 20-, 30-, 40-, 50-, 55-, and 57- at .% Pt to determine the distribution of magnetic moments. We find that the average Ni and Pt moments decrease slowly out to about 50- at .% Pt and beyond that decrease rapidly toward zero at the critical concentration of 58- at .% Pt. The moment disturbance functions show peaks in the forward direction corresponding to moment disturbance effects that become increasingly longer ranged with increasing Pt content implying inhomogeneous moment distributions.
Abstract: Magnetic and thermal anomalies of Invar alloys
Authors: Matsui M. , Adachi K. , Chikazumi S.
Published: February 2003

The anomalous thermal expansion coefficient of Fe-Ni Invar alloys has been well explained1) in terms of the two-state model of an Fe atom.2) The analysis of the thermal expansion coefficient (α) of disordered phase of Fe-Pt Invar alloys in terms of the Grüneisen equation shows that the anomalous part of α has negative values in the whole temperature region with monotonic temperature dependence and remains even at high tempertures above the ferromagnetic Curie point. These behaviors are similar to that of Fe-Ni Invar alloys. The ferromagnetic moment becomes unstable in the Invar region. The calculation of a molecular field approximation in terms of the two-state model, assuming the distribution of the ferromagnetic nature of the high spin state as well as the low spin state, shows that the magnetic moment at 0 °K and Curie point decrease and the temperature dependence of the magnetization deviates from the Brillouin function in the Invar region. The temperature dependence of the susceptibility of Fe-Ni alloys has been measured. The inverse susceptibility deviates from the Curie-Weiss law at high temperatures. The deviation is due to the temperature dependence of the number of the low spin states of Fe atoms. It has been clarified by means of the measurement of the integrated intensity of the X-ray diffraction experiment of Fe-Ni Invar alloys that the Debye temperature decreases at low temperatures, regarded as a lattice softening effect. The static deviation effect from the ordinary lattice point is also contained in the integrated intensity of the X-ray diffraction. The static deviation of atoms is large in Invar alloys and comes from the mixing of the two states of an Fe atom.

1 M. Matsui and S. Chikazumi J. Phys. Soc. Japan 45, 453 (1978).

2 R. J. Weiss, Proc. Phys. Soc. 32, 281 (1963).
Extraordinary Hall effect in Ni-Fe-Cr ternary alloys
Authors: Sinha A. , Majumdar A. K.
Published: February 2003

The Hall resistivity, the ohmic resistivity and the saturation magnetization have been measured in Ni-Fe-Cr ternary alloys at 300K and 77K. The ’split-band model’ predicts a line on the Ni-Fe-Me ternary diagram (Me=V, Cr, Mo, W) along which the Fermi level passes through the point of intersection of Ni and Fe spin-down bands. The extra-ordinary Hall conductivity γHs and the linear magnetostriction λs are supposed to pass through zero values and change their signs while crossing the line. Our data shows that the experimental γHs?0 line is far below the theoretical line and may be slightly below the experimental λs?0 line. The values of the Curie temperature Tc and the magnetization Ms vary roughly linearly with Cr content. Ms is calculated on the basis of Fridel’s theory of virtually bound states of Cr. The agreement with experiments is good for temperatures well below Tc.
Polarized neutron study of CeSn3 (invited)
Authors: Stassis C. , Loong C.-K. , Harmon B. N. , Liu S. H. , Moon R. M.
Published: February 2003

Over the past several years there has been considerable interest in materials exhibiting a nonintegral valence. As a result the properties of cerium metal and its compounds have been the subject of many theoretical and experimental investigations. In the present experiment polarized neutron scattering techniques have been used to study the spatial distribution and temperature dependence of the magnetization induced in a single crystal of CeSn3 by a magnetic field of 42.5 kG. In the 40–300 K temperature range the measured magnetic form factor is in good agreement with the 4f magnetic form factor of Ce3+. Below 40 K, on the other hand, the magnetic form factor measurements suggest that the induced magnetization contains a large component of 5d electronic character of eg symmetry, which can account, at least partly, for the increase in the magnetic susceptibility of CeSn3 at low temperatures. The results will be discussed in terms of a model in which the 4f level is positioned slightly above the Fermi energy and is hybridized with the conduction band. Band theoretical calculations have been performed to determine the nature of the electronic wavefunctions at the Fermi level.
First order phase transitions and the three state Potts model
Authors: Blöte H. W. J. , Swendsen R. H.
Published: February 2003

We have used the Monte Carlo renormalization group method to study the order-disorder phase transition of the three and four dimensional, three-state Potts model. In both cases, the transition appears to be first order. However, no evidence for a discontinuity fixed point associated with these transitions was found. Instead, the existence of a nearby second order fixed point just beyond the first order transition could be inferred from the RG flow in the ordered as well as in the disordered state. These results imply that the thermodynamic quantities are analytically continuable into the metastable regions, and that apart from discontinuities caused by the intersection of the two free-energy branches, no additional singularities occur at the transition.
Monte Carlo simulation of the cubic model
Authors: Sablik M. J. , Cook M. , Vuong N. , Phani L. , Zawonski M. , Phani M.
Published: February 2003

The cubic model, described by the Hamiltonian ⋅=−JΣ<ij≳ σiσjδαiδαj where σi=±1 and αi=x, y, or z, is subjected to a Monte Carlo simulation. For an 8×8×8 fcc lattice, it is found that the system exhibits a first order transition at kBTo/J=3.45±0.01 in fairly close agreement with results obtained previously by the Kikuchi approximation. Discontinuities at the phase transition and stability limits for the metastable states on either side of the phase transition are also investigated.
Heisenberg chains with alternating spin quantum numbers
Authors: Blöte H. W. J.
Published: February 2003

In linear magnetic Heisenberg chains, alternation effects can be caused by alternation of the spin quantum numbers. These effects are found to be different from those caused by alternation of the interaction constant. When one of the spin quantum numbers is infinite (i.e. can be treated classically) and the other arbitrary, the zero field partition function and thermodynamical quantities can be obtained analytically. The susceptibility of the infinite spin sublattice can also be derived. Spin-wave theory predicts that the dispersion relation is split into an acoustic and an optic branch, of which only the latter has a gap. The acoustic branch behaves essentially ferromagnetically, except in the uniform antiferromagnetic limit.
Amorphous YFe2—A concentrated spin glass
Authors: Forester D. W. , Koon N. C. , Schelleng J. H. , Rhyne J. J.
Published: February 2003

Magnetic susceptibility, Mössbauer, and neutron scattering studies of the same alloy sample all indicate that amorphous YFe2 (a-YFe2) exhibits spin-glass behavior with a truly thermodynamic spin-glass transition at TS.G.=58K. These studies show that spin-glass behavior can persist to quite high magnetic concentrations in an amorphous alloy system which is dominated by competing ferromagnetic and antiferromagnetic exchange interactions. At a lower temperature of T?20K, the susceptibility versus T curve shows a break and the coercive field is anomalous. We interpret this phenomenon near T=20K as arising from magnetic ’’blocking’’ of individual spins or regions of correlated spins which persist below TS.G.. This produces a cluster-freezing-type ’’pseudo-transition’’ which is merely a manifestation of the slowing down of spin fluctuations to a time interval comparable with the experimental susceptibility measurement time. The temperature dependence of the spin-glass order parameter is obtained from the susceptibility results and is in close agreement with data generated by Monte-Carlo simulations.
Very low temperature magnetization of two dilute PdMn alloys
Authors: Thomson J. O. , Thompson J. R.
Published: February 2003

A SQUID Magnetometer has been used to measure the temperature dependent magnetization of two dilute alloys of Mn in Pd. Results are presented for temperatures T of 0.01 to 1 Kelvin, for applied magnetizing fields Ha of 0.5 to 600 Oe, for samples containing 255 and 575 atomic ppm of Mn. This dilute alloy system displays a remarkable variation in its properties. For the concentration region under study, PdMn may be described as a giant-moment spin glass. (1) At low field and high temperature, the magnetization M follows a Curie-Weiss law, M = CHa/ (T−ϑ), with positive (ferromagnetic) ϑ values of 31 and 78 mK, respectively. From the Curie constant we obtain a ’’giant’’ effective moment per Mn impurity, p of 11 μB (μB = Bohr magneton). With spin S = 5/2, this gives an effective g value of g = 3.7. (2) From the highest field data we estimate the saturation moment per Mn spin gSμB to be 9 μB; with S = 5/2, this gives g = 3.6 in good agreement. (3) As the temperature is lowered in constant applied field the magnetization becomes independent of temperature, a behavior which is characteristic of the total DC magnetization of a spin glass at low temperatures.
Some unforeseen advances in basic magnetism during the past twenty-five years (invited)
Authors: Rado George T.
Published: February 2003

The twenty-fifth anniversary of the annual Conference on Magnetism and Magnetic Materials offers an appropriate occasion for assessing the significance and physical basis of some unforeseen but important advances in basic magnetism since the middle 1950’s. Three of these advances are (a) the one-ion (or crystalline field) mechanism of magnetocrystalline anisotropy energy which was synthesized from ingredients investigated in paramagnets and developed into a practical tool for ’’designing’’ ferrimagnets; (b) the recognition of the degeneracy of the spin wave spectrum in ferrimagnetic insulators and its contribution to the establishment of the previously mysterious origins of relaxation in ferrimagnetic resonance; and (c) the concept of magnetic symmetry and its role in ’’legitimizing’’ the previously ’’forbidden’’ (and unobserved) magnetoelectric effect, piezomagnetism, and other phenomena involving considerations of time reversal. Some of these advances occurred gradually rather than abruptly, and none of them appear to have conformed to a pre-programmed schedule of short-range goals, milestones, and payoffs. What these advances do have in common is that they were motivated by a need or desire for basic understanding and that they originated in the recognition of a hidden problem or even in unforeseen flashes of physical insight.
Spin-glass versus ’’blocking’’ in dilute EuxSr1−xS
Authors: Tholence J. L.
Published: February 2003

The properties of this dilute insulator have been studied by two groups, either on single crystals or on powders. In single crystals, spin-glass properties (maximum of the susceptibility at Tf ∝ x) are observed down to x = 0.05. They are attributed to an essential role of the dipolar interaction. Below this concentration the blocking of isolated ferromagnetic pairs at Tp becomes predominant since Tp (concentration independent) becomes larger than Tf. In powders, an identical behavior is observed below x = 0.05. A more complex behavior, described by the blocking of magnetic clusters, is observed for 0.05 < x < 0.13 and spin-glass properties are only observed for x ≳ 0.13. Thus, the observation of a ’’dipolar spin-glass’’ in a dilute insulator depends on the sample preparation; it requires confirmation.
Abstract: Magnetoresistance through the spin-glass regime of amorphous Fe-Ni-P-B
Authors: Gudmundsson H. , Rao K. V. , Anderson A. C. , Brandt Bruce , Egami T.
Published: February 2003

We report first detailed magnetoresistance (MR) studies of amorphous magnetically dilute FexNi1−xP14B6 alloys with x=3,5,7,11 and 13, in applied fields, B, to 22 T and for temperatures above 0.1 K. The resistance minimum, observed in all these alloys, occurs at a maximum temperature of 100 K for x=5 alloy, a consentration at which a transition from spin glass to mictomagnetic behavior has been reported.1 The (MR) in all these alloys, which can be as large as −1%, has a strong T-dependence over a wide temperature range both below and above the spin freezing temperature Tf (or Tc for x≳11). Above Tf(Tc) the B dependence of (MR) is −ve but with a curvature indicative of cluster effects. Also even at 0.2 K no saturation effects are observed in the −ve (MR) up to 22 T. The overall rise in resistance R(T)/Rmin decreases with increasing Fe conc. for x≳5. It is striking that for all these alloys the resistance is found to increase with decreasing T even at 0.1 K with no indications of any spin freezing effects. Thus the low T resistivity behavior of these amorphous alloys is markedly different from those usually observed in crystalline spin glasses. Supported by NSF grants DMR 77−08599 and DMR 76−80994 resp. 1David Onn et al., J. Appl. Phys. 49(3), 1730 (1978).
Abstract: Spin wave resonance in amorphous ferrimagnetic GdCoMoAr alloy film
Authors: Mizoguchi T. , Kobliska R. J. , Maekawa S. , Imazu T.
Published: February 2003

Spin wave resonances, observed in an amorphous Gd6.9Co74Mo12.8Ar6.3 ferrimagnetic alloy film, indicate that the exchange stiffness constant, A, decreases rapidly with increasing temperature. By extension of spin-wave theory to ferrimagnets, the temperature dependence of A has been interpreted in terms of a two sub-network ferrimagnet.(AIP)
Micromagnetics of curling configurations in magnetically soft cylinders
Authors: Arrott A. S. , Heinrich B. , Templeton T. L. , Aharoni Amikam
Published: February 2003

The response of an ideally soft magnetic cylinder is calculated by approximating magnetostatic interactions while taking into account the exchange energy of curling patterns with point singularities. Detailed calculations of the magnetic surface charge distribution of paramagnetic materials are used as a guide in parameterizing an approximate charge distribution suitable for applying the Ritz method to the micromagnetic problem of ferromagnetic materials without anisotropy or magnetostriction. Numerical results are given for a cylinder with L/D=1 for fields below saturation illustrating how remanence and coercivity depend on the ratio of the exchange length A/M2o to sample dimensions. The role of point singularities in remanence, coercivity, nucleation and irreversibility is outlined.
Super-alignment of magnetic particles on coated discs and its effects on the recording characteristics
Authors: Itoh K. , Ishida S. , Hamada M. , Ogawa S.
Published: February 2003

In order to predict the future trend of the magnetic disc media, we tried to increase the orientation ratio of magnetic particles on γ-Fe2O3 coated discs. By refining the technique of paint-making, we have realized super-aligned discs having longitudinal squareness, Mr/Mm of 0.92 and halfwidth of differential M-H curve, ΔH of 95 Oe with unexpectedly smooth surface. The recording characteristics of the superaligned discs and variously oriented discs were measured using a Mn-Zn ferrite head. It is found that the reproduced output of highly-oriented discs is larger than is expected from the increase in Mr and that the half pulsewidth decreases with an increase in Mr/Mm. This suggests the orientation also causes a reduction of magnetization transition length, a. Taking the effect of squareness into consideration, a simple empirical relation, a=ΔH/Hc⋅2tMr/Hc, was introduced and the obtained data were well explained with this relation. From these results and low noise characteristics of oriented discs, we conclude that the highly-oriented γ-FeO3 coated discs will be suitable for higher recording density, up to 15,000 BPI and 1,000 TPI, having a sufficient S/N ratio.
Phonon assisted magnon transmission through nickel at 24 GHz
Authors: Heinrich B. , Cochran J. F.
Published: February 2003

According to conventional theories of microwave transmission through ferromagnetic metals the transmission of 24 GHz radiation through nickel slabs 5–10 μm thick should be unobservable. Nevertheless, experiments at room temperature have revealed a peak in the transmission of 24 GHz microwaves at FMR using nickel single crystals and annealed polycrystalline foils ca. 8 μm thick. It is proposed that this anomalous energy transport across the specimens at FMR is due to the phonon mode which is generated by magneto-elastic coupling to the resonantly precessing magnetization. The calculations indicate that exchange plays a significant role in determining the intensity and the lineshape of the transmitted signal at FMR.
Magnetic properties of pseudo-ternaries of the composition Nd(Mn1−xCrx)2Si2
Authors: Obermyer R. , Sankar S. G. , Rao V. U. S.
Published: February 2003

Structural and magnetic properties of a number of pseudo-ternaries of the composition Nd(Mn1−xCrx)2Si2 have been examined. In the composition range 0<x<0.6 they crystallize in tetragonal BaAl4-type structure. Magnetic properties were examined between 4.2 K and 400 K in applied fields up to 20 kOe. NdMn2Si2 exhibits anomalies in the magnetization versus temperature plots at about 40 K and 380 K—the former due to the ordering of the rare earth moments and the latter due to the ordering of the transition metal sublattice. Addition of chromium to this compound increases the crystal cell volume significantly and modifies the magnetic behavior. The transition metal sublattice orders antiferromagnetically at 380 K, 260 K and 200 K for compositions of X=0, 0.2 and 0.3, respectively. Compounds of the composition X=0.2, 0.3 and 0.4 exhibit unusual thermomagnetic hystereses. The thermomagnetic curves for these compositions in low external fields (<10 kOe) exhibit an increase in the magnetization upon warming the sample from 4.2 K to about 30 K. Above this temperature the rare earth sublattice begins to disorder. These results are interpreted on the basis of a model considering the competition of exchange interactions of the rare earth and transition metal sublattices. The possibility of modifying the nature of magnetic interaction between rare earth and Mn atoms through the incorporation of a second transition metal atom (in this instance Cr) into the lattice will be discussed. Experimental data obtained for the compositions of X=0.2, 0.3 and 0.4 seem to indicate that the rare earth ion changes its easy direction of magnetization from the easy c-axis to the basal plane (or cone) as the material is cooled below 50 K.