Showing papers on "Magnetization published in 1973"
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
TL;DR: In this paper, it was shown that a previously unknown class of magnetization patterns exists in planar structures which have the unique property that all the flux escapes from one surface with none leaving the other side.
Abstract: It is shown that a previously unknown class of magnetization patterns exists in planar structures which have the unique property that all the flux escapes from one surface with none leaving the other side. A simple case is a constant amplitude rotating vector magnetization where the sense of rotation dictates which surface has no flux. More complicated magnetization patterns are elucidated. The likelihood that the one-sided flux phenomenon occurs partially in the normal write, the contact-printing and the print-through processes of tape recording is discussed. It is concluded that significant improvements in tape recording performance would ensue if means could be found to enhance the effect.
263 citations
TL;DR: In this article, the rare earth contribution to the magnetocrystalline anisotropy in RCo5 and R2Co17 compounds with a single ion model using a Hamiltonian of the form: H= B 2 0 O 2 0 +gμ B J·H ex Hex is regarded as arising mainly from the cobalt sublattice.
249 citations
TL;DR: A general expression is developed for the quasi-static magnetic field outside an inhomogeneous nonmagnetic volume conductor containing internal electromotive forces and it is shown that the external magnetic field vanishes under conditions of axial symmetry.
219 citations
TL;DR: The mechanism by which these sediments acquired their natural remanent magnetism (NRM) is still poorly understood as discussed by the authors, however, it has been shown that post-depositional re-manent magnetisation is a viable mechanism of magnetisation of deep-sea sediments.
Abstract: SEDIMENTS of various lithologies cored from most parts of the deep ocean floor have been found to contain a record of the past behaviour of the Earth's magnetic field, especially the sequence of reversals over at least the past 5 my (ref 1) The mechanism by which these sediments acquired their natural remanent magnetism (NRM) is, however, still poorly understood We have recently conducted experiments that indicate that post-depositional remanent magnetisation2 is a viable mechanism of magnetisation of deep-sea sediments
176 citations
TL;DR: In this article, the sublattice magnetization data were not in agreement with those previously published but do agree with data for other orthoferrites and for iron oxides in general.
Abstract: The ferroelectric and antiferromagnetic orthoferrite BiFeO3 has been studied extensively using the Mossbauer effect technique The sublattice magnetization data are not in agreement with those previously published but do agree with data for other orthoferrites and for iron oxides in general The several phase transition reported in the literature have not been observed
159 citations
TL;DR: In this paper, the authors used the Moessbaurr effect in 57Fe to determine the direction of magnetization in the HoxTb1-xFe2, HoxEr 1-x Fe2, Dy/sub x/Tb 1-XFe2, DyxE1-exFe2/, and Hox Tm1-oxFe2 systems as a function of x and temperature.
Abstract: Directions of the easy magnetization in the HoxTb1-xFe2 , HoxEr1-x Fe2, Dy/sub x/Tb1-xFe2, DyxE1-xFe2/, and Hox Tm1-xFe2 systems were determined as a function of x and temperature by means of the Moessbaurr effect in 57Fe. If the direction of magnetization of each system is described by a (x,T) spin-- orientation diagram, it is found that the (x,T) plane is divided into two or three regions, in each of which the direction of magnetization is along a different major crystal axis. Theoretical calculations based on the assumption that the magnetic crystalline anistropy is due to the anisotropy of the interaction between the 4f electrons of the rare-earth ions with the crystal fields reproduced the general features of the experimental results though small discrepancies remained. Taking into account an additional contribution to the anisotropy attributed to the Fe -- Fe interaction improved the agreement between the theoretical and experimental spin-orientation diagrams. From the theoretical fits to the experimental results a value of (--0.038 plus or minus parameters A6/A4. The transitions between the regions of the spin--orientation diagrams are not sharp. Possible reasons for the existence of the transition regions are discussed. (9 figures, 3 tables, 15 references) (auth)
155 citations
TL;DR: In this paper, high-field magnetization studies were made from 4 °K to room temperature on rapidly sputtered TbFe2, DyFe2 and SmFe2.
Abstract: High‐field magnetization studies were made from 4 °K to room temperature on rapidly sputtered TbFe2, DyFe2, and SmFe2. At 4.2 °K the magnetic moment resembles that of polycrystal samples, whereas at room temperature it is substantially lower. Huge coercive forces (20–30 kOe) were observed at 4.2 °K. Partial crystallization of TbFe2 from the sputtered amorphous state yields high‐energy products and coercivities (> 3 kOe) at room temperature.
133 citations
TL;DR: In this article, four theories of magnetic viscosity are reviewed in an attempt to interpret the very different viscous properties of these two types of rocks, including the Richter and Neel theories for soils and low-grade breccias, whereas igneous and recrystallized rocks are better described by the multidomain theories of Neel (1950 and Stacey (1963).
Abstract: Lunar materials exhibit two distinct types of viscous or time-dependent magnetic behavior. Igneous rocks and largely recrystallized breccias, whose magnetic properties are due to multidomain iron, typically have weak magnetic viscosity, but decay persists for very long times following even a brief exposure to a field. Lunar soils and low metamorphic grade breccias, which contain an important fraction of metallic iron of single-domain and superparamagnetic size, generally acquire an anomalously strong viscous remanence, whose decay time is about equal to the time of exposure to the field. Four theories of magnetic viscosity are reviewed in this paper in an attempt to interpret the very different viscous properties of these two types of rocks. The Richter (1937) and Neel (1949) theories are appropriate to soils and low-grade breccias, whereas igneous and recrystallized rocks are better described by the multidomain theories of Neel (1950) and Stacey (1963). Both the Stacey and Neel theories correctly predict logarithmic magnetic viscosity, in spite of the fact that the central role played by the internal demagnetizing field in multidomain grains is ignored in Neel's formulation. This apparent paradox has been resolved. Analysis of the particularly simple case of a two-domain particle shows that the distribution of asymmetrical nonidentical potential barriers required by Neel is automatically generated from the simpler distribution of symmetrical identical barriers proposed by Stacey through the action of the demagnetizing field. Experimental evidence on many facets of viscous magnetization, from terrestrial as well as lunar materials, is reviewed in detail before a final evaluation of the various theories is made. One interesting conclusion is that the magnetic viscosity of multidomain particles, although relatively weak, is still too strong to be explained by displacements of entire domain walls. Either displacements of small wall segments or rotation of pseudo-single-domain moments could account for the enhancement of magnetic viscosity in these particles.
115 citations
TL;DR: In this paper, measurements of the NRM of a 26 m long deep-sea core from the southern Indian Ocean indicated the presence of three transitions of magnetic polarity which have been identified as the upper and lower Jaramillo and the upper Olduvai on the basis of micropaleontological criteria.
110 citations
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.
TL;DR: In this paper, the effect of oxidization on the intensity of the remanent magnetization was measured, and it was shown that the increase in remanent intensity at the higher oxidation temperatures is associated with the unmixing of the titanomaghemite that forms during oxidation.
Abstract: Natural crystals of a titanomagnetite were oxidized in an excited oxygen gas at temperatures that were varied from 50° to 200°C, and the effect of oxidation on the intensity of the remanent magnetization was measured. Oxidation of the titanomagnetite, which was extracted by dry grinding from a submarine basalt, produced two separate types of behavior. When the temperature of oxidation was 135°C or above, oxidation produced an increase in the intensity of the original remanence and a chemical remanence that was stronger than the original remanence in the sample. When the temperature of oxidation was below 135°C, oxidation produced a decrease in the intensity of the initial remanence and a chemical component that was less intense than the original remanence. Both types of oxidation produced a chemical magnetization having higher coercivity than the original remanence during af demagnetization. The increase in remanent intensity at the higher oxidation temperatures is shown to be associated with the unmixing of the titanomaghemite that forms during oxidation.
TL;DR: In this article, the magnetic ordering of planar antiferromagnet was confirmed to be of the planar type with a power law over the range $6\ifmmode\times\else\texttimes\fi
Abstract: Elastic and inelastic neutron-scattering studies of the planar antiferromagnet ${\mathrm{K}}_{2}$Mn${\mathrm{F}}_{4}$ have been carried out. The magnetic ordering is confirmed to be of the ${\mathrm{K}}_{2}$Ni${\mathrm{F}}_{4}$ type with ${T}_{N}=42.14$ K; no evidence is found for the additional ${T}_{N}=58$ K phase reported by Ikeda and Hirakawa (IH). The sublattice magnetization is found to follow a single power law over the range $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}l\frac{1\ensuremath{-}T}{42.14}l3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1}$, with $\ensuremath{\beta}=0.15\ifmmode\pm\else\textpm\fi{}0.01$. This contrasts with the results of IH, who report $\ensuremath{\beta}=0.188$ up to $\frac{1\ensuremath{-}T}{{T}_{N}}=5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ with a crossover to three-dimensional behavior beyond $\frac{1\ensuremath{-}T}{{T}_{N}}=5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The effects of a distribution of N\'eel temperatures on neutron order-parameter determinations is discussed, and it is shown that the apparent crossover behavior observed by IH can be accounted for on the basis of a distribution of ${T}_{N}'\mathrm{s}$ with standard deviation 50 mK in their crystal. The spin-wave dispersion relations in the (${q}_{x},0,{q}_{z}$) plane have been measured at 4.5 K and at ${T}_{N}$. The spin waves correspond precisely to those expected for a simple quadratic anisotropic Heisenberg antiferromagnet with ${J}_{1}=8.45\ifmmode\pm\else\textpm\fi{}0.1 \mathrm{K}$, $g{\ensuremath{\mu}}_{B}{H}_{A}=0.32 \mathrm{K}$, and all other exchange interactions below our resolution limit. These values are in excellent accord with those determined from the susceptibility by Breed and from the sublattice magnetization and AFMR by de Wijn et al., and they thence confirm that simple two-dimensional spin-wave theory gives a complete description of the low-temperature magnetic properties of ${\mathrm{K}}_{2}$Mn${\mathrm{F}}_{4}$. Well-defined spin waves are observed up to ${T}_{N}$; at ${T}_{N}$ the (${q}_{x},0,0$) dispersion relation is a simple sine wave with slope renormalized by $\ensuremath{\sim}9%$ from the 4.5-K value; this renormalization is correctly predicted by the $\frac{1}{S}$ Oguchi correction terms.
TL;DR: In this article, the authors presented numerical calculations of magnetic dipole moments, magnetic octupole moments and transition probabilities in odd-mass nuclei around 208 Pb. The calculations were performed in the framework of the theory of finite Fermi systems with an effective magnetic operator.
TL;DR: In this article, the authors analyzed the effect of cross-relaxation on the recovery of the longitudinal magnetization after a perturbation on a simple exponential curve described by a single time constant T1.
TL;DR: In this paper, a thermodynamic theory for some types of dielectric and magnetic relaxation phenomena is developed, where a polar and an axial vector field occur as internal thermodynamic degrees of freedom and that these fields influence the polarization and magnetization, respectively.
TL;DR: In this article, a soil of Attica (Greece) has been studied by M6ssbauer spectroscopy and magnetization measurements in order to ascertain the nature and form of iron oxides present in it.
Abstract: A soil of Attica (Greece) has been studied by M6ssbauer spectroscopy and magnetization measurements in order to ascertain the nature and form of iron oxides present in it. The room tempera- ture spectra consist of a paramagnetic doublet and a small magnetic sextet. At liquid nitrogen tempera- ture the magnetic component increases considerably at the cost of the paramagnetic component. This behavior is typical of superparamagnetism exhibited by ultrafine magnetic particles. From the values of hyperfine parameters extracted by computer fits of the spectra, the particles can be identified mainly as a-Fe203. The theory of superparamagnetism, in conjunction with M6ssbauer and magnetiza- tion data, is discussed in detail. Application of this theory to the data for the clay fraction of the soil leads to the conclusion that the oxide particles have a size distribution with a mean particle diameter of 131 A and a width of 14 A.
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.
TL;DR: In this paper, the effects of substituting bismuth into various single crystal iron garnets have been investigated and it was shown that the magnitude of the contribution depends on the concentrations of tetrahedrally coordinated Fe3+ions, suggesting that both these ions are involved in the transition responsible for the additional rotation.
Abstract: This paper describes the effects on Faraday rotation and optical absorption of substituting bismuth into various single crystal iron garnets. The large negative contribution to the Faraday rotation produced by the presence of bismuth is of the diamagnetic form and is associated with an optical transition around 415 nm. The magnitude of the bismuth contribution depends on the concentrations of bismuth and tetrahedrally coordinated Fe3+ions, suggesting that both these ions are involved in the transition responsible for the additional rotation. The absorption arising from the bismuth increases with decreasing wavelengths. However, the increase in magnitude of the rotation is such that the figure of merit is increased above that of YIG, peaking at 560 nm with a value of 5.2 deg/dB. The Faraday rotation and figure of merit of low magnetization garnets, suitable for magnetooptic devices, are also increased in the visible by the presence of bismuth.
TL;DR: In this paper, the superparamagnetic relaxation time for spherical particles with cubic magnetocrystalline anistropy, whose easy axis is either [100] or [111] in zero applied field, was calculated.
Abstract: The superparamagnetic relaxation time is calculated for spherical particles with cubic magnetocrystalline anistropy, whose easy axis is either [100] or [111] in zero applied field. Results are reported for relatively small particles only, in which no anomaly is found. It is concluded that the experimentally observed anomaly in this size region must be due to incoherent magnetization reversals.
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.
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.
TL;DR: In this paper, a variational method was proposed to calculate the width and energy of a wall in a film and the twist angle of the wall magnetization in the midplane of the film.
Abstract: The magnetic field due to surface charge distorts the internal structure of domain walls in films as compared to those in an infinite medium. In the midplane of the film the wall magnetization is parallel to the wall plane (for stationary walls), but near the film surface it is ``twisted'' into a direction that can be almost perpendicular to the wall plane. The width and energy of such walls and the twist angle have been calculated by a variational method for uniaxial anisotropy and stationary plane walls. For very thick films (film thickness » wall width in an infinite medium) the reciprocal wall width and the wall energy are smaller than the values for an untwisted wall by approximately a factor of (1−0.65σ)1/2, where σ=4πM0/Ha, M0 is the saturation magnetization, and Ha the uniaxial anisotropy field. For very thin films they are smaller by a factor of (1−σ)1/2.
TL;DR: In this article, self-consistent spin-polarized APW calculations have been performed to determine the energy band structure of metallic vanadium in an assumed ferromagnetic b.c. structure as a function of lattice parameter.
TL;DR: Hard bubbles in typical bubble garnets can be eliminated by ion implantation, which produces a layer of planar magnetization at least a few hundred angstroms thick.
Abstract: Hard bubbles in typical bubble garnets can be eliminated by ion implantation which produces a layer of planar magnetization at least a few hundred angstroms thick. Neon at doses in the 1014‐ions/cm2 range is as effective as hydrogen at doses in the 1016‐ions/cm2 range in suppressing hard bubbles without effecting domain wall coercivity or mobility. Annealing studies have shown that the thermal stability of the effect increases with increasing dose and decreasing energy of implantation and is sufficient to withstand maximum device processing temperatures and assure long lifetimes.
TL;DR: In this article, the proton spin-lattice relaxation time was measured in a crystalline powder of NH 4 ClO 4 from room temperature to 4°K at Larmor frequencies of 22 and 56 MHz.
TL;DR: In this paper, the systematics of ten mercury isotopes, for which there exist precision measurements of both the nuclear magnetic dipole moments and hfs interaction constants A (6s 6p 3P1), were examined.
TL;DR: In this paper, the ferromagnetic domain structure was studied in 3% Si-Fe single crystals during magnetization using the longitudinal Kerr effect and high speed cinematography, and large and variable wall spacings were observed during 60 Hz magnetization with no evidence of wall bowing.
Abstract: The ferromagnetic domain structure was studied in 3% Si-Fe single crystals during magnetization using the longitudinal Kerr effect and high speed cinematography. Large and variable wall spacings were observed during 60 Hz magnetization with no evidence of wall bowing in a crystal with perfect