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Showing papers on "Ferromagnetism published in 1973"


Journal ArticleDOI
TL;DR: In this paper, the effect of spin fluctuations on itinerant electron ferromagnetism was extended to include the ferromagnetic phase and the correction to the Hartree-Fock free energy as a function of magnetization was expressed in terms of the transversal dynamical susceptibilities.
Abstract: The theory of the effect of spin fluctuations on itinerant electron ferromagnetism, which we have developed previously, is extended to include the ferromagnetic phase. The correction to the Hartree-Fock free energy as a function of magnetization is expressed in terms of the transversal dynamical susceptibilities and is actually calculated by using a modified random phase approximation for the dynamical susceptibilities; the random phase approximation is modified so as to give a consistent static limit throughout the whole temperature range covering both below and above the Curie point. As a result, the magnetization at low temperatures shows a T 3/2 dependence due to the spin wave excitations, the Curie temperature is generally lowered from the Stoner (Hartree-Fock) value and the magnetic susceptibility above the Curie temperature shows an approximate Curie-Weiss behavior.

307 citations


Book
19 Nov 1973
TL;DR: In this article, the authors proposed a method to calculate the magnetic field by means of current sheets and showed that the current sheet can be used to calculate magnetic field in the presence of a single magnet.
Abstract: 1. Methods of Magnetic Field Generation.- 1.1 High Magnetic Field Laboratories.- 1.2 Conventional Continuous Duty Magnets with and without Iron.- 1.3 Pulsed Magnets.- 1.4 Cryogenic Magnets.- 1.5 Superconducting Coils.- References.- 2. Magnetic Field Calculations.- 2.1 Magnets without Ferromagnetic Yokes.- 2.1.1 Magnetic Fields due to Current Elements.- 2.1.2 Fields due to Filamentary Current Lines.- 2.1.3 Field Corrections.- 2.1.4 Applications.- 2.1.4.1 Circular Current Filament.- 2.1.4.2 Elliptical Conductor.- 2.1.4.3 Dipole Field.- 2.1.4.4 Quadrupole Field.- 2.1.5 Magnetic Field Calculation by Means of Current Sheets.- 2.1.6 Magnetic Field of Cylindrical Coils.- 2.1.6.1 Use of Spherical Harmonics, Axially-Symmetric Coils.- 2.1.7 Magnetic Field of Non-Cylindrical Coils.- 2.1.8 Fields Produced by Means of Distributed Parallel Conductors.- 2.1.8.1 Multipole Coils with Circular Aperture.- 2.1.9 Multipole Coils with Rectangular Aperture.- 2.2 Magnetic Fields due to Coils in Proximity to Ferromagnetic-Materials.- 2.2.1 Introduction.- 2.2.2 Direct Current Magnetization Curves.- 2.2.3 Difference Equations.- 2.2.4 The Grid System.- 2.2.5 Field Intensity in Rectangular Coordinates.- 2.2.6 Finite Difference Equations in Cylindrical Coordinates.- 2.2.7 Field Intensity in Cylindrical Coordinates.- 2.2.8 Field Problem as a Set of Simultaneous Equations.- 2.2.9 Boundaries with Different Permeabilities.- 2.2.10 Right-Angle Boundary with Different Permeabilities on Each Side.- 2.2.11 Curved Boundaries.- 2.2.12 General Boundary Condition.- 2.2.13 Solution of Difference Equations.- 2.2.14 Concept of Residuals.- 2.2.15 A Computational Method.- 2.2.16 The Iron-Air Interface.- 2.2.17 Examples and Results of Numerical Computations.- 2.2.17.1 Superconducting Dipole Magnets.- 2.2.17.2 Superconducting Quadrupole Magnet.- 2.2.17.3 Axially-Symmetric Magnets.- 2.2.17.4 General.- 2.3 Field Calculation of Iron-Bound Air-Core Magnets.- 2.3.1 Current Sheet.- 2.3.2 Coils of Finite Thickness.- 2.3.3 Special Cases.- 2.3.4 The Coil Ampere-Turns.- 2.3.5 The Magnetic Vector Potential.- 2.3.6 The Inner Radius of the Iron Shield.- 2.3.7 Iron Radial Thickness.- 2.3.8 Stored Energy.- 2.3.9 Magnetic Fields due to Axially-Symmetric Iron Distribution.- 2.4 Calculation of Forces.- 2.4.1 Forces due to Coil-Winding.- 2.4.2 Forces due to Thermal Contraction.- 2.4.3 Magnetomechanical Forces Fm.- 2.4.4 Magnetomechanical Forces due to Winding Pretension.- 2.4.5 Magnetomechanical Forces in Cylindrical Geometrics.- 2.4.6 Stresses due to Thermal Contraction.- 2.4.7 Forces for a Dipole Coil Configuration.- 2.4.8 Force Equations for Multipole Coils.- 2.4.9 Forces in Spherical Coils.- 2.4.10 Forces in Toroidal Coils.- 2.5 Calculation of Heating.- References.- 3. Phenomena and Theory of Superconductivity.- 3.1 Theory.- 3.1.1 Introduction.- 3.1.2 Free Electron Theory.- 3.1.3 Zero Field Properties of a BCS Superconductor.- 3.1.4 Superconductors in an Applied Field.- 3.1.5 Type II Superconductors.- 3.1.6 Summary of Free-Electron, BCS and GLAG Formulae.- 3.2 Critical Fields of Type II Superconductors.- 3.2.1 Introduction.- 3.2.2 Magnetostatics and Thermodynamics of Type I Superconductors.- 3.2.3 Intermediate State of Type I Superconductors.- 3.2.4 The Mixed State of Type II Superconductors.- 3.2.5 Exact Theories of the Mixed State.- 3.2.6 Paramagnetic and Impurity Effects on Hc2.- 3.2.7 Critical Fields of intermetallic Compounds.- 3.2.8 Surface Superconductivity.- 3.3 Critical Currents of Type II Superconductors.- 3.3.1 Introduction.- 3.3.2 Forces on Flux Lines.- 3.3.3 Flux Flow.- 3.3.4 Thermally Activated Flux Creep.- 3.3.4.1 Thermally Activated Flux Creep.- 3.3.4.2 Calculation of the Effective Density of Vortex Pinning Sites.- 3.3.4.3 Nature of Vortex Pinning Sites.- 3.3.5 Low Temperature Experimental Results on the Field and Defect Dependence of the Critical Current Density.- 3.3.5.1 High Field Materials.- 3.3.5.2 Low Field Materials.- 3.3.5.3 Other Low Temperature Effects.- 3.3.6 Kim Anderson Theory at Finite Temperatures.- 3.3.7 A.C. Effects.- 3.3.8 Conclusions.- References.- 4. Superconducting Alternating Current Magnets.- 4.1 Alternating Current Losses.- 4.1.1 Introduction.- 4.1.2 Flux Profiles.- 4.1.3 Thin Superconducting Tapes and Filaments.- 4.1.4 Finite Size Slabs and Cylindrical Conductors Located in a Transverse External Field.- 4.1.5 Methods of Calculating Hysteretic Losses due to Alternating Fields.- 4.1.6 Hysteretic Losses in Slabs.- 4.1.7 Application to Multifilamentary Conductors.- 4.1.8 Hysteretic Losses in Cylindrical Shaped Superconductors.- 4.1.9 Hysteretic Losses in Coils Using Hollow Superconducting Filaments.- 4.1.10 Losses in Composites.- 4.1.11 Eddy Current Losses in the Conductor Matrix.- 4.1.12 Self Field Losses.- 4.1.13 Contribution of External Fields.- 4.1.14 Discussion.- 4.1.15 Comparison between Self-Field and Hysteretic Losses.- 4.1.16 Modification of the Hysteretic Losses, if the Transport Current is not Zero.- 4.2 Additional Effects in Twisted Multifilamentary Conductors.- 4.2.1 Axial Diffusion of the Self Field.- 4.2.2 Solution of I (r, z, t).- 4.2.3 Extension of the Self Field Model in Twisted Multi-Filament Conductors.- 4.3 Eddy Current Losses in Metallic Parts.- 4.3.1 Iron Losses in the Flux Return Path.- 4.3.2 Eddy Current Losses in the Metallic Cryostat.- 4.4 Multifilamentary Conductors.- 4.4.1 Cables and Braids.- 4.5 Comparison of Loss-Calculation with Experiments.- 4.6 Methods of Loss Measurement.- 4.6.1 Calorimetric Method.- 4.6.2 Electric Methods.- 4.7 Magnetic and Thermal Instabilities.- 4.7.1 Introduction.- 4.7.2 Diffusion Equations.- 4.7.2.1 Magnetic Diffusivity.- 4.7.2.2 Thermal Diffusivity.- 4.7.3 Stability.- 4.7.3.1 Temperature Rise from Fluxjump.- 4.7.3.2 Adiabatic Stability.- 4.7.3.3 Dynamic Stability.- 4.7.3.4 Steady State Stability.- 4.8 A.C. Magnet Fabrication Techniques.- 4.8.1 Coil Fabrication.- 4.8.2 Electrical-Design.- 4.8.2.1 Current Leads.- 4.8.2.2 Superconductor to Lead Joints.- 4.8.3.1 Transient Voltages in Coils due to Quenches.- 4.9 Irradiation Effects in Superconducting Magnets.- 4.9.1 Introduction.- 4.9.2 Energy Loss by Collisions.- 4.9.3 Irradiation Effects on Type II Superconductors.- 4.9.4 Irradiation Effects on Normal Metals.- 4.9.5 Irradiation Effects on Magnet Insulations and Reinforcements.- 4.9.6 Irradiation Effects on Helium.- References.- 5. Cryogenics.- 5.1 General Properties of Cryogenic Fluids.- 5.1.1 Availability and Production.- 5.2 Low Temperature Processes.- 5.2.1 Handling Cryogenic Fluids.- 5.2.1.1 Safety Precautions.- 5.2.2 Transferring Cryogenic Fluids.- 5.2.3 Liquid Level Measurement.- 5.2.3.1 Introduction.- 5.2.3.2 Methods of Level Measurement.- 5.3 Liquefaction and Refrigeration.- 5.3.1 Basic Principles, Reversible Cycles.- 5.3.2 Efficiency of Real Cycles.- 5.3.3 Non-Isothermal Refrigeration.- 5.3.4 Practical Refrigerators.- 5.3.5 Liquefiers.- 5.3.6 Real Liquefiers.- 5.4 Handling and Storage of Cryogenic Fluids.- 5.5 Physical Properties of Cryogenic Fluids.- 5.5.1 Helium.- 5.5.2 Hydrogen.- 5.5.3 Nitrogen.- 5.6 Physical Properties of Solids.- 5.6.1 Introduction.- 5.6.2 Mechanical Properties of Solids.- 5.6.2.1 Stress-Creep Relation.- 5.6.2.2 Stress-Strain Relation.- 5.6.2.3 Fatigue.- 5.6.3 The Work of Fracture.- 5.6.4 Thermal and Transport Properties of Solids.- 5.7 Heat Losses.- 5.7.1 Heat Conduction.- 5.7.2 Convection.- 5.7.3 Radiation.- 5.7.4 Methods to Minimize Thermal Losses.- 5.7.5 Application.- References.- 6. Economic Consideration in the Design of Water-Cooled, Cryogenic and Superconducting Magnets.- 6.1 Introduction.- 6.2 Cost Comparison for Specific Magnet Systems.- 6.2.1 Solenoids and Split Coils.- 6.2.2 Water-Cooled Solenoids with Uniform Current Density Distribution.- 6.2.3 Cryogenic Magnets with Uniform Current Density Distribution.- 6.2.4 Superconducting Magnets.- 6.2.5 Operating Cost of Superconducting Coils.- 6.2.6 Long Solenoids.- 6.2.7 Magnets for Energy Storage.- 6.2.8 Beam Transport and Accelerator Magnets.- 6.3 Cost Comparison in General.- References.- 7. Examples of Superconducting Magnet Systems.- 7.1 The Argonne National Laboratory 3.7-m Hydrogen Bubble-Chamber Magnet.- 7.2 The CERN Liquid Hydrogen Bubble-Chamber Magnet.- 7.3 Composite Magnet System, the McGill and MIT Hybrid Magnets.- 7.4 The Oak-Ridge -IMP -Superconducting Coil System.- 7.5 The SLAC 7 T, 30-cm Bore, Helmholtz Magnet.- References.

188 citations


Journal ArticleDOI
TL;DR: In this paper, a simple expression for the magnetoresistance of the antiferromagnetic metals due to the electron-spin scattering by the s -d interaction is obtained using the molecular field approximation for the spin system.
Abstract: A simple expression for the magnetoresistance of the antiferromagnetic metals due to the electron-spin scattering by the s - d interaction is obtained using the molecular field approximation for the spin system The expression includes the ferromagnetic case It is shown that in the antiferromagnetic case the positive magnetoresistance appears below the transition point, in contrast to the negative-magnetoresistance in the case of the para or ferromagnetic case In the ferromagnetic case the negative magnetoresistance shows a deep and finite valley at the transition point, which is consistant with the experiments of the ferromagnetic rare-earth metals such as Gd and Tb

178 citations


Journal ArticleDOI
TL;DR: In this paper, the equation of state and the static correlations in a system of spherical ferromagnetic grains suspended in a magnetically passive fluid were discussed and the possibility of resonances in the small-angle X-ray scattering was demonstrated.
Abstract: We discuss the equation of state and the static correlations in a system of spherical ferromagnetic grains suspended in a magnetically passive fluid. In the domain where dipole-dipole interactions between the grains are large (low temperature) we show that the variation of the small-angle X-ray scattering with magnetic field provides a sensitive test of the model proposed to treat this system. We discuss the condensation of the grains into linear chains at low density, high magnetic field, and low temperature. The possibility of resonances in the small-angle X-ray scattering is demonstrated and certain other consequences of chain formation are indicated.

139 citations


Journal ArticleDOI
TL;DR: In this paper, a specific model for the origin of ferromagnetism in Fe is assumed, which attributes the origin to the indirect coupling of localized d-like electrons by a small number of itinerant d electrons.
Abstract: A specific model for the origin of ferromagnetism in Fe is assumed which attributes the origin of the ferromagnetism to the indirect coupling of localized d‐like electrons by a small number of itinerant d electrons. We find that about 5% of the d‐electrons are in itinerant d bands; the other 95% being in d‐bands which are sufficiently narrow that they can be considered localized. Band calculations and Fermi surface measurements strongly support such a model. Using this model we give the scaling rules for the three contributions to the hyperfine field at any solute atom in an Fe, Co or Ni matrix and evaluate some of these contributions. The analysis indicates that the CEP curves for 4s electrons of Co and Ni are similar to that measured for Fe. Thus the origin of ferromagnetism in Co and Ni is also assumed to be due to a small fraction of itinerant d electrons in these metals.

135 citations


Journal ArticleDOI
TL;DR: In this article, the self energy expression obtained from a Ward identity has a simple alternative diagrammatic derivation in terms of electron-magnon scattering processes and the question of the stability of strong ferromagnetism in the Hubbard model is considered.
Abstract: For pt. I, see ibid., vol.3, no.12, 2174 (1973). The strongly ferromagnetic limit of the theory developed in the preceding paper is examined in detail. The self energy expression obtained there from a Ward identity has a simple alternative diagrammatic derivation in terms of electron-magnon scattering processes. General features of the resultant single particle excitation spectrum are investigated and the question of the stability of strong ferromagnetism in the Hubbard model is considered. Numerical calculations of self energies, spectral weight functions and densities of states are presented for a simple spherically symmetric band structure whose parameters are chosen to simulate the band structure of nickel. Experimental implications of the work are discussed.

110 citations


Journal ArticleDOI
TL;DR: In this article, the polarization change of a polarized neutron beam after transmission through a partly magnetized ferromagnetic material can be described by a (3×3) depolarization matrix.
Abstract: The polarization change of a polarized neutron beam after transmission through a partly magnetized ferromagnetic material can be described by a (3×3) depolarization matrix. A theory has been developed to interpret this matrix in terms of well-known magnetic domain quantities such as the reduced mean magnetizationm, the mean domain size δ and the mean square direction cosines γ x , γ y and γ z of the inner magnetization within the domains. In order to do this it was necessary to make some simplifying assumptions about ferromagnetic domain structures. The influences of these assumptions on the quantities derived have been discussed. Finally the theory has been applied to depolarization measurements in nickel foils with the magnetic field and mechanical stress as parameters.

108 citations


Journal ArticleDOI
TL;DR: In this paper, the requirements of spin conservation in the form of a Ward identity, are exploited to make a selfconsistent theory of itinerant ferromagnetism in terms of electron-magnon interactions.
Abstract: The requirements of spin conservation in the form of a Ward identity, are exploited to make a selfconsistent theory of itinerant ferromagnetism in terms of electron-magnon interactions. Earlier results are extended to weak ferromagnets and the structure of self energies and single particle spectral weight functions is discussed. The theory is also applied to the calculation of the spin wave stiffness constant.

100 citations


Journal ArticleDOI
TL;DR: In this article, a general theory of spin-dependent phonon Raman scattering in magnetic crystals is developed, where the integrated Raman intensity as a function of temperature is expressed as S (T )=( n 0 + 1)| R + M | 2, where the first term represents the spin independent part and the second one the spin- dependent part which is proportional to the nearest neighbor spin correlation function.
Abstract: A general theory of the spin-dependent phonon Raman scattering in magnetic crystals is developed. The integrated Raman intensity as a function of temperature is expressed as S ( T )=( n 0 +1)| R + M | 2 , where the first term represents the spin-independent part and the second one the spin-dependent part which is proportional to the nearest neighbor spin correlation function . Three types of temperature variation of intensity are predicted in ferromagnetic and antiferromagnetic cases, depending on values of R / M . Two microscopic mechanisms, variation of the d electron transfer with lattice vibrations and that of the non-diagonal exchange, contribute to the spin-dependent part, and it is shown that the former is essentially important in producing the large temperature variation. The theory is applied to explaining the observed temperature variation of various Raman active phonon modes in CdCr 2 S 4 and the experimental results are explained successfully.

83 citations


Journal ArticleDOI
TL;DR: The presence of the crystalline electric field is felt rather strongly by the 4 ¼ shells of Pr and Nd in this environment so that these materials are exchange enhanced ferromagnets as mentioned in this paper.
Abstract: RNiAl and RCuAl crystallize with the Fe 2 P structure. This structure type is less densely packed than the Laves phases. Most of these materials order ferro-magnetically at low temperature but ErNiAl and TmNiAl, which according to the de Gennes function should exhibit relatively weak ferromagnetism, are shown to be subtle metamagnets. The presence of the crystalline electric field is felt rather strongly by the 4ƒ shells of Pr and Nd in this environment so that these materials are exchange enhanced ferromagnets.

82 citations


Journal ArticleDOI
TL;DR: In this article, the difference between the magnitudes and thermal evolutions of the magnetic susceptibilities are explained in terms of ferromagnetic vs antiferromagnetic superexchange enhancement and large vs small spin polarons associated with excited states.

Journal ArticleDOI
TL;DR: In this article, the spin polarization of deuterons scattered from magnetized ferromagnetic nickel is determined via the T(d, n) 4 He reaction via T(n) He reaction, and the predominant electron spin orientation is found parallel to the magnetizing field for electrons in (100, (110, (111)-, (120)-surfaces.

Journal ArticleDOI
TL;DR: In this paper, a change in the electric quadrupole interaction was observed from 460 to 480 K and interpreted as a result of the rotation of the easy axis of magnetization as a function of temperature.
Abstract: Moessbauer absorption spectra have been observed for Fe2B from 290 to 1175 K. A change in the electric quadrupole interaction was observed from 460 to 480 K and interpreted as a result of the rotation of the easy axis of magnetization as a function of temperature. The effective magnetic hyperfine field is defined as a function of temperature. A discontinuity in the isomer shift of 0.018 (plus or minus 0.010) mm/sec was found across the ferromagnetic transition.

Journal ArticleDOI
TL;DR: In this article, the critical behavior of an anisotropic classical Heisenberg ferromagnet with cubic point-group symmetry was studied in the limit where the spin dimensionality N is large.
Abstract: The critical behavior of an anisotropic classical Heisenberg ferromagnet with cubic point-group symmetry is studied in the limit where the spin-dimensionality N is large. The system is shown to undergo a first order phase transition. Corrections of order 1/N are calculated for a critical exponent describing the behaviour of the transverse susceptibility in zero magnetic field below the critical temperature. For small anisotropy and to order 1/N the equation of state is identical to the isotropic calculation when expressed in terms of longitudinal and transverse susceptibilities, temperature and magnetization, except for a shift in the critical temperature.


Journal ArticleDOI
TL;DR: The static magnetic susceptibility and the ESR spectra from 1.6 to 300 K have been measured on a powder sample of the titled free radical and the broad maximum in the susceptibility which indicates an antiferromagnetic interaction has been observed at 6.9 K as discussed by the authors.
Abstract: The static magnetic susceptibility and the ESR spectra from 1.6 to 300 K have been measured on a powder sample of the titled free radical. The broad maximum in the susceptibility which indicates an antiferromagnetic interaction has been observed at 6.9 K. The broadening of the ESR absorption line and the shift of the g-value have been found in the temperature region below Tmax, in which the susceptibility reached its round maximum. There appeared anomalies in the slope of the susceptibility, the linewidth, and the g-value versus temperature curves in the vicinity of 1.7 K. These anomalies may imply a magnetic-phase transition from the short-range ordered state to the long-range ordered state at about 1.7 K. The existence of a ferromagnetic interaction between the magnetic chains in the triphenylverdazyl radical solid is discussed on the basis of the susceptibility, the spin distribution, and the crystal structure. It is understood qualitatively that the radical with a negative spin density has a latent fe...

Patent
12 Jan 1973
TL;DR: A magnetic medical treatment device having a plurality of magnets or magnetic shells arranged so arranged that the same polarity poles of the magnet or magnetic shell closely contact a selected part of a human body such that polarization and induced currents are efficiently generated in the human body is described in this article.
Abstract: A magnetic medical treatment device having a plurality of magnets or magnetic shells so arranged that the same polarity poles of the magnets or magnetic shells closely contact a selected part of a human body such that polarization and induced currents are efficiently generated in the human body Each of the magnetic shells of the same polarity is provided with a ferromagnetic metal plate on the side thereof opposite the body contacting sides of the magnetic shells

Journal ArticleDOI
K.H.J. Buschow1
TL;DR: The magnetic properties of rare earth-magnesium compounds with the CsCl structure have been determined in the temperature range 4.2-300 K with applied magnetic fields up to 18 kOe.
Abstract: The magnetic properties of rare earth-magnesium compounds with the CsCl structure have been determined in the temperature range 4.2–300 K with applied magnetic fields up to 18 kOe. There is a change in sign of the asymptotic Curie temperatures in going from compounds with light rare-earth elements to those with heavy rare-earth elements. The temperature dependence of the magnetization in the magnetically ordered region points to antiferromagnetism for the former compounds and to ferromagnetism for the latter compounds. For all compounds investigated the lattice constants have been determined.

Journal ArticleDOI
TL;DR: In this article, the energy dispersion relation of spin waves in CoCl2 at temperatures between 4.4 K and 34 K was investigated and it was shown that the interplanar exchange interactions are much weaker than those within the planes, giving rise to the'metamagnetic' property of ferromagnetic saturation in relatively weak magnetic fields.
Abstract: Neutron scattering has been used to investigate the energy dispersion relation of spin waves in CoCl2 at temperatures between 4.4 K and 34 K. CoCl2 orders antiferromagnetically at TN=24.9 K with the Co2+ spins lying within ferromagnetic planes which are antiferromagnetically stacked along the hexagonal c axis. The interplanar exchange interactions are much weaker than those within the planes, giving rise to the 'metamagnetic' property of ferromagnetic saturation in relatively weak magnetic fields, and suggesting that above TN there could be correlations between spins appropriate to a two-dimensional ferromagnet. The observed spin waves at low temperature indeed only exhibit strong dispersion within the basal plane and measurement of this dispersion enables an accurate value for the nearest-neighbour exchange constant to be determined.

Patent
09 Jul 1973
TL;DR: In this paper, a dynamoelectric machine has a number of low flow density, high coercive force permanent magnets mounted in its ferromagnetic core to improve the magnetic field of the machine.
Abstract: A dynamoelectric machine having a number of low flow density, high coercive force permanent magnets mounted in its ferromagnetic core to improve the magnetic field of the machine. The magnets are positioned within a preferred range of angular orientation with respect to the main flux path of the machine to maximize magnetic flux density in the core without exceeding the core saturation flux density. The ratio of the flux density of the magnets at their maximum energy point and the core saturation flux density determines the preferred range of angles of retention of the magnets.

Journal ArticleDOI
TL;DR: In this article, the crystal structure of KCrS2 has been confirmed and the paramagnetic Curie temperature is +112 K, indicating that the ferromagnetic interaction in the sheets is the dominant one.

Journal ArticleDOI
TL;DR: A qualitative explanation of the effect of structural disorder on magnetic properties of the Co and Fe compounds is given in terms of the consequences of charge transfer to the transition metal atoms as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, the magnetic properties of TiFe x Co 1-x have been measured at temperatures between 4.2 and 300 K and interpreted in terms of a weak itinerant electron ferromagnet model.
Abstract: Magnetic properties of TiFe x Co 1- x have been measured at temperatures between 4.2 and 300 K. For the compositions of 0.4≦ x ≦0.8 they are interpreted in terms of a weak itinerant electron ferromagnet model. The slope in the M 2 versus H / M curves rapidly increases with decreasing of iron concentration, which is in good agreement with the result expected from the electronic specific heat coefficient.

Journal ArticleDOI
TL;DR: By neutron diffraction and susceptibility measurements the crystallographic and magnetic structures of (CH3NH3)2MnCl4 and (CD3ND3) 2mcl4 have been investigated as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, the authors present a theoretical calculation of the behavior of the density of states, free energy and order parameter of very thin superconductors in a high magnetic field as a function of spin-orhit and spin-flip impurity scattering.
Abstract: Using Green's-function techniques, we present a theoretical calculation of the behavior of the density of states, free energy, and order parameter of very thin superconductors in a high magnetic field as a function of spin-orhit and spin-flip impurity scattering. In very thin superconducting films without spin scattering, the upper critical field is determined by the Pauli paramagnetism of the nomnal-metal electrons. Tunneling measurements by Meservey and Tedrow have shown a spin splitting by 2 mu /sub B/H in energy space of the BCS peak in the density of states. Zero-temperature calculations of the separate up- and down-spin Green's function for a superconductor show that spin-orbit impurities destroy the magnetic field separation of the peaks in the density of states but do not destroy the energy gap. Spin-flip scattering is much more destructivc and destroys both the separation oi the peaks and the energy gap. We generalize the calculation to T plus or minus 0 and calculate and plot the critical field versus temperature and the magnetic field dependence of the free energy and order parameter for the various values of the spin-orbit and spin-flip parameter. We also use the theoretical calculations to obtain a fit to the low- temperature tunnelingmore » data of Meservey and Tedrow between thin Al and a normal metal and the spin-polarized tunneling between thin Al and ferromagnetic metals. (auth)« less


Journal ArticleDOI
TL;DR: In this paper, the self-diffusion coefficients of iron in α-iron and in Fe-Cr alloys in the temperature range 660-890°C and in the concentration interval 0-11.8 wt.% Cr were determined.

Journal ArticleDOI
TL;DR: The magnetic properties of tetragonal LiTbF4 are reported for the first time in this article, where a transition to an uniaxial, high-anisotropy, ferromagnetic state is observed at Tc = 2.86 ± 0.03 K.

Journal ArticleDOI
TL;DR: In this article, a theory of the residual electrical resistance of disordered alloys is presented in the framework of the coherent-potential approximation, which can be applied to calculate the concentration dependence of magnetization, spin-up and spin-down resistivities, and spontaneous resistivity anisotropy of ferromagnetic alloys.
Abstract: A theory of the residual electrical resistance of ferromagnetic disordered alloys is presented in the framework of the coherent-potential approximation. It generalizes a previous calculation made for a two-band model Hamiltonian relevant for transition-metal-based alloys. This formalism can be applied to calculate the concentration dependence of magnetization, spin-up and spin-down resistivities, and spontaneous resistivity anisotropy of ferromagnetic alloys. These quantities are computed for a simple model of NiCu and are found to be in good agreement with observation.

Journal ArticleDOI
TL;DR: In this paper, a model which is capable of explaining the observed effects is proposed to explain the differences in reflected and back-scattered electron yield from domains magnetized in different directions.
Abstract: Contrast arising from the domain structure of ferromagnetic materials with cubic anisotropy has been observed in the scanning electron microscope. The contrast is due to differences in reflected and back-scattered electron yield from domains magnetized in different directions. A model which is capable of explaining the observed effects is proposed.