scispace - formally typeset
Search or ask a question

Showing papers on "Magnetization published in 1977"


Journal ArticleDOI
TL;DR: In this article, it was suggested that a second-order transition from an antiferromagnetic to a Kondo spin-compensated ground state will occur as the exchange coupling constant J is increased to a critical value Jc for systems in which J ≲ Jc.
Abstract: By considering a one-dimensional analog of a system of conduction electrons exchange coupled to a localized spin in each cell of a lattice, it is suggested that a second-order transition from an antiferromagnetic to a Kondo spin-compensated ground state will occur as the exchange coupling constant J is increased to a critical value Jc For systems in which J ≲ Jc, a very weak sublattice magnetization may occur as a result of nearly complete spin-compensation

1,309 citations


Journal ArticleDOI
TL;DR: In this paper, a new perpendicular magnetic recording system is proposed for high density recording, which uses the perpendicular magnetization mode which is basically free from the demagnetization in very high densities.
Abstract: By the analysis of the self-consistent magnetization and the direct observation of the remanent magnetization of a real tape, the authors discussed the obstacles which are, and will be, encountered in attaining a higher recording densities with the present magnetic recording system, which uses mainly a longitudinal magnetization mode. Then the properties of the three magnetization modes (longitudinal, circular, and perpendicular) are compared. The mode transformation is also discussed. Finally a new perpendicular magnetic recording system is proposed for high density recording. And some results of fundamental experiments are presented. The system uses the perpendicular magnetization mode which is basically free from the demagnetization in very high densities. Its realization mainly owes to the development of a perpendicular anisotropy film and perpendicular magnetic heads.

463 citations


Journal ArticleDOI
TL;DR: ErRh4B4 becomes superconducting at a critical temperature T c 1 of 8.7 K followed by a return to the normal state at a second critical temperature t c 2 of 0.9 K.
Abstract: The compound ErRh4B4 becomes superconducting at a critical temperature T c1 of 8.7 K followed by a return to the normal state at a second critical temperature T c2 of 0.9 K. The return to the normal state at T c2 is coincident with the occurrence of long-range ordering of the magnetic moments of the Er 3+ ions which completely occupy a set of equivalent lattice sites.

433 citations



Journal ArticleDOI
Masuo Suzuki1
TL;DR: In this article, a general phenomenological theory of spin-glasses is presented, which predicts the weak singularities (like cusps) of susceptibilities and specific heat near the transition point TsG and also predicts generally the divergence of the second derivative of the nonlinear susceptibilities with respect to a magnetic field in zero field at Tsa.
Abstract: A general phenomenological theory of spin-glasses is presented, which predicts the weak singularities (like cusps) of susceptibilities and specific heat near the transition point TsG and also predicts generally the divergence of the second derivative of the nonlinear suscepti­ bility with respect to a magnetic field in zero field at Tsa. A similar second derivative of specific heat is also shown to diverge at Tsa except for the molecular field theory. Scaling equations of state for magnetization m and spin-glass order-parameter q are derived, which yield new scaling relations of critical exponents for m(T), q(T), X,(T), Co(T) and the corresponding nonlinear quantities. These general results explain qualitatively very well the magnetic field dependence of magnetization and specific heat observed experimentally. A non-uniform phenomenological Hamiltonian is also proposed for the rcnormalization group approach, which yields the critical dimensionality d,=6, as usuaL Intermediate random statistics and real replica method are p;oposed. There is also presented an exactly soluble model showing a spin-glass like phase transition.

298 citations


Journal ArticleDOI
Mamoru Mekata1
TL;DR: In this article, the magnetic properties of a triangular Ising lattice with antiferromagnetic nearest neighbor interaction and ferromagnetic second neighbor interaction were investigated at finite-temperature.
Abstract: Molecular field approximation is applied to a triangular Ising lattice with antiferromagnetic nearest neighbor interaction J and ferromagnetic second neighbor interaction J ' to study the magnetic behavior at finite temperatures. In the range of 0> J '/ J >-0.8, with increasing temperature the system is found to have a second-order transition from a ferrimagnetic state to an antiferromagnetic state in which one of three sublattices is completely disordered. Another second-order transition occurs in the ferrimagnetic state. Magnetic structure factor, free energy, magnetic specific heat, differential magnetic susceptibility as well as sub-lattice magnetization are calculated numerically with parameter J '/ J . Critical magnetic field of first-order transition from antiferromagnetic state to ferrimagnetic state is also evaluated. Discussion is given in connection with magnetic ordering in CsCoCl 3 and CsCoBr 3 .

247 citations


Journal ArticleDOI
TL;DR: In this paper, measurements of magnetization, electrical resistivity, thermal expansion and differential thermal change were made on amorphous Fe 100-x B x (9 ≦ X ≦ 21) alloys prepared by rapid quenching from the liquid state.

151 citations


Patent
05 Jul 1977
TL;DR: A magnetic recording medium comprising a magnetic sheet of domain sized particles of at least one member selected from the group consisting of barium ferrite, strontium and lead ferrite is defined in this paper.
Abstract: A magnetic recording medium comprising a magnetic sheet of domain sized particles of at least one member selected from the group consisting of barium ferrite, strontium ferrite and lead ferrite, dispersed uniformly in an organic binder, and a ferromagnetic plate bonded to one surface with the other surface of the sheet being magnetizable at selected sites with the magnetization being in a direction substantially perpendicular to the surfaces.

130 citations


Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of hexagonal Fe 2 P single crystal are studied by the measurements of magnetization, susceptibility, thermal expansion and electrical resistivity along the principal crystallographic axes.
Abstract: The magnetic properties of hexagonal Fe 2 P single crystal are studied by the measurements of magnetization, susceptibility, thermal expansion and electrical resistivity along the principal crystallographic axes. It is found that the saturation magnetization per molecule and the Curie temperature are 2.94 µ B and 208.6 K, respectively, and the anisotropy constant K 1 is 2.32×10 7 erg/cm 3 at 4.2 K, which is considerably larger than the values in 3d-transition compounds. The thermal expansion and the electrical resistivity show discontinuous changes at the Curie temperature indicating that the ferromagnetic to paramagnetic transition of Fe 2 P is accompanied by the first-order transition due to magnetoelastic effects. The exchange striction obtained from the measurement of thermal expansion is discussed on the basis of the theory of Bean and Rodbell.

120 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derive a new inequality for ferromagnetic Ising spin systems and then use it to obtain information about the number of phases which can coexist in such systems.
Abstract: We derive a new inequality for ferromagnetic Ising spin systems and then use it to obtain information about the number of phases which can coexist in such systems. We show in particular that for even interactions only two phases (up and down magnetization) can coexist below the critical temperature at zero magnetic field (h=0) whenever the energy is a continuous function of the temperature. We also prove that the derivatives with respect toh ath=0 of the odd correlation functions (triplet,...) diverge like the susceptibility in the vicinity of the critical temperature (at least for pair interactions). Our results also apply to higher order Ising spins (not just spin 1/2).

105 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the temperature variation of the magnetic fields at the two non-equivalent B-sites is proportional to the sublattice magnetization, suggesting that the deviations arise from a variation in band overlap.
Abstract: Mossbauer spectroscopic studies (57Fe) of powdered magnetite have been undertaken between 120 K and 880 K. Below the magnetic transition temperature (T C=839.5 K) three six-line patterns have been fitted to our experimental spectra. The broadening of the B-pattern is explained by two magnetically non-equivalent B-site irons, suggesting broadening due to electron hopping to be negligible. In the paramagnetic state the electric quadrupole splittings of iron at A-and B-sites are found to be constant, independent of temperature, having the values zero and 0.16 mm/s, respectively. The centroid shifts, on the other hand, show above 700 K large deviations from the calculated second order Doppler shift. It is proposed that the deviations arise from a variation in band overlap. The temperature variation of the magnetic fields is found to be proportional to the sublattice magnetization. The difference in the magnetic fields at the two non-equivalent B-sites is measured to be 1.1 T at 310 K.

Journal ArticleDOI
TL;DR: In this paper, a paramagnetic (I)-ferromagnetic (II)-sinusoidal (III) phase diagram near a Lifshitz point is studied for the case of uniaxial magnetization.
Abstract: A paramagnetic (I)-ferromagnetic (II)-sinusoidal (III) phase diagram near a Lifshitz point is studied for the case of uniaxial magnetization. The shape of the phase diagram in the vicinity of this point is determined. It is found that the II \ensuremath{\rightleftarrows} III phase transition line is tangent to the order-disorder (I \ensuremath{\rightleftarrows} II and I \ensuremath{\rightleftarrows} III) transition line at the Lifshitz point. The II \ensuremath{\rightleftarrows} III phase transition is shown to be first order, with latent heat and metastability regions. The behavior of magnetic susceptibility is determined. Binary alloy systems are suggested in which the considered type of phase diagram may be expected.

Journal ArticleDOI
TL;DR: In this paper, thermal fluctuations of polarization, magnetization, and associated electromagnetic fields in dielectric magnetic media are considered and the correlation functions can be expressed in terms of the Green functions for Maxwell's equations.
Abstract: We consider thermal fluctuations of polarization, magnetization, and the associated electromagnetic fields in dielectric magnetic media which are allowed to be anisotropic and spatially nonhomogeneous. The theory is purely macroscopic and is based on an application of the fluctuation–dissipation theorem. It is shown that the correlation functions can be elegantly expressed in terms of the Green functions for Maxwell’s equations.

Journal ArticleDOI
TL;DR: In this paper, the properties of a mixture of two anisotropic antiferro-magnets with different easy axes have been analyzed both in mean field approximation and in the method of distribution function.
Abstract: Thermal and magnetic properties of a mixture of two anisotropic antiferro-magnets with different easy axes have been analyzed both in mean field approximation and in the method of distribution function. A new phase called OAF phase is found within a certain range of concentration. In OAF phase, the spin of each species of ion on a sublattice has each own axis of sublattice magnetization tilting oblique to the easy axes of the pure systems. As temperature increases, OAF phase makes a transition into the antiferromagnetic phase and then to the paramagnetic phase successively. It is expected that these transitions are detected by measurements of specific heats for a powder sample and of susceptibilities for a single crystal. It is also pointed out that magnetization processes show some characteristic features of OAF phase.

Journal ArticleDOI
TL;DR: In this article, spontaneous relaxation of the local 4f magnetization due to interconfiguration fluctuation between 4f/sup 1/ and 4f /sup 0/ was interpreted.
Abstract: Diffuse neutron scattering on the intermediate valence compound CePd/sub 3/ shows a quasi-elastic line with Lorentzian shape and very large, nearly temperature-independent width (GAMMA/2 approx. = 20 meV). The intensity under this line has 4f form factor but the total cross section indicates only 0.5 4f electron per formula unit. These observations are interpreted by spontaneous relaxation of the local 4f magnetization due to interconfiguration fluctuation between 4f/sup 1/ and 4f/sup 0/.

Journal ArticleDOI
TL;DR: In this paper, it is shown that the analytical relationship between the total magnetic field or the gravity effect and equivalent magnetization or density on an arbitrary observational surface is given by a Fredholm integral equation of the second kind.
Abstract: The problem of reduction of magnetic and gravity data, when observed on an arbitrary surface in a region of high topographic relief, is studied with equivalent source representation at the points of observation. It is shown that the analytical relationship between the total magnetic field or the gravity effect and equivalent magnetization or density on an arbitrary observational surface is given by a Fredholm integral equation of the second kind. A rapidly convergent iterative scheme is described for the solution of the integral equation, yielding the surface distribution of magnetization or density. With this distribution, the field at any other surface can be easily computed. Then it has been demonstrated with model examples that the gravity or magnetic field observed on a rough terrain can be accurately reduced to a horizontal plane for processing and interpretation.A new method has been suggested for minimization of terrain-induced anomalies on a magnetic or gravity map. This method is based on the concept that when the anomalous field observed on an arbitrary surface is continued to a surface parallel to the topography, the terrain effect in the continued field is sharply reduced relative to the field created by bodies of finite extent in the crust. Model examples are presented to show the accuracy and reliability of the method.

Journal ArticleDOI
Abstract: In the basic spinel NiFe2O4, ions of larger and larger ionic radius, Zn2+ and Cd2+, have been introduced with higher and higher concentrations. The corresponding materials of composition Ni1-xZnxFe2O4 and Ni1-xCdxFe2O4 have been prepared by using a special technologic process. The lattice constant increases linearly with the mean ionic radius in tetrahedral site. The variation of the Curie temperature due to a variation of the distance between magnetic ions is evaluated. The contribution to the Curie temperature due to the magnetic carriers distribution is shown by plotting a single intercomposition hypothetic curve. In the same way the influence upon the magnetization value of the variation of the distance between magnetic ions has been evaluated. Results obtained on spinels have been compared with those deduced from literature data in the case of garnets.

Journal ArticleDOI
TL;DR: In this article, a number of 3D, 4d and 5d elements are substituted into Fe3Si in an attempt to form Heusler-like alloys, and the limits of solubility in Fe3 Si are determined.

Journal ArticleDOI
TL;DR: In this article, a sensitive Colpitts oscillator circuit monitored the spatial and temporal variations in magnetization in a vertical 11 cm column of magnetic fluid, and the results are consistent with the hypothesis that spherical agglomerates of 10 7 -10 9 particles are formed and settle gravitationally.

Journal ArticleDOI
TL;DR: In this paper, exact expressions for the time-dependent correlation functions of the x and y component of the magnetization for the one-dimensional anisotropic XY-model (S = 1 2 ) in zero field in the high-temperature limit were derived.
Abstract: Exact expressions are derived for the time-dependent correlation functions of the x and y component of the magnetization for the one-dimensional anisotropic XY-model ( S= 1 2 ) in zero field in the high-temperature limit. As a corollary, the correlation functions for the Ising chain in a transverse field are obtained.

Journal ArticleDOI
TL;DR: In this article, the magnetic and crystallographic properties of the (FeMn)3Si system have been studied by X-ray and neutron diffraction magnetization resistivity and magnetoresistivity measurements.
Abstract: Magnetic and crystallographic properties of the (FeMn)3Si system have been studied by X-ray and neutron diffraction magnetization resistivity and magnetoresistivity measurements. The single-phase alloys have been found to crystallize in the L21A structure and to have ferromagnetic properties at low Mn concentrations. At higher concentrations the alloys exhibit a more complex behaviour, having antiferromagnetic components below a temperature TR which is almost concentration independent. The resistivity showed anomalies at TR as well as at the Curie point. The variation of the magnetic moment on each site has been determined as a function of concentration and is discussed in terms of environmental changes occurring as a result of Mn additions.

Journal ArticleDOI
TL;DR: In this article, the experimental situation in connection with theoretical models is discussed, with a special emphasis on the experimental situations of surface magnetization, including dead layers, live layers, surface anisotropy, and magnetic proximity effects.

Journal ArticleDOI
TL;DR: In this article, a reversal mode, domain wall inversion or curling, is proposed to explain the incoherent reversal of domain wall moments, which consists of nucleating and propagating a Bloch line across a 180° domain wall.
Abstract: At least four types of sub-domain magnetic moments, on a scale smaller than the main domain structure, could contribute to pseudo-single-domain intensities of TRM (thermoremanent magnetization) in small multidomain grains. Of these, moments pinned by the stress fields of dislocations, surface moments, and moments due to the Barkhausen discreteness of domain wall positions are either strongly shielded by the magnetically soft matrix, subject to the internal demagnetizing field during magnetization changes, or so coupled to the domain structure that they cannot change magnetization independently. Only the net moments of domain walls themselves qualify as ‘psarks’—subdomain moments with truly single-domain behaviour. A new reversal mode, domain wall inversion or curling, is postulated to explain the incoherent reversal of domain wall moments. It amounts to nucleating and propagating a Bloch line across a 180° domain wall.

Journal ArticleDOI
TL;DR: In this paper, it was shown that if Z is some vectorial internal degree of freedom which influences the polarization, bip(int) may be defined which is a function of biZ, which may replace biZ as vectorial external degree and which is part of the total specific polarization.
Abstract: It has been shown by the author in a previous paper that thermodynamic vectorial internal degrees of freedom which influence the polarization or the magnetization of a medium may give rise to dielectric or magnetic relaxation phenomena. Snoek's equation for magnetic relaxation phenomena was derived and it was shown that Debye's theory for dielectric after-effects in polar liquids is a special case of the developed theory. In this paper it is shown that if Z is some vectorial internal degree of freedom which influences the polarization a new internal degree of freedom bip(int) may be defined which is a function of biZ, which may replace biZ as vectorial internal degree of freedom and which is a part of the total specific polarization. Furthermore, p(int) may be introduced in such a way that the remaining part of the polarization, p(el) (defined by p ( el ) = p − p int ) , where p is the total polarization per unit of mass), has the property that it vanishes for all values of p(int) if the medium is in a state where the electric field E and the mechanical elastic stresses vanish and the temperature of the medium equals some reference temperature. If the equations of state are linearized the latter result implies for an isotropic medium E =ρa (0,0) (bdp) p ( el ) , where ρ is the mass density and a(0,0)(P) a constant. On the other hand p(int) satifies a relaxation equation. It is seen that the use of p(int) as an internal degree of freedom is of great advantage. This is connected with the fact that p(int) is a measurable quantity in contradistinction to an arbitrary “hidden” vectorial internal degree of freedom. Analogous results may be obtained for magnetic after-effects.

Journal ArticleDOI
TL;DR: The Mariner 10 spacecraft encountered Mercury three times in 1974-1975 as mentioned in this paper, and the first and third encounters provided detailed observations of a well-developed detached bow shock wave which results from the interaction of the solar wind.
Abstract: The Mariner 10 spacecraft encountered Mercury three times in 1974-1975. The first and third encounters provided detailed observations of a well-developed detached bow shock wave which results from the interaction of the solar wind. The planet possesses a global magnetic field and a modest magnetosphere, which deflects the solar wind. The field is approximately dipolar, with orientation in the same sense as earth, tilted 12 deg from the rotation axis. The magnetic moment corresponds to an undistorted equatorial field intensity of 350 gammas, approximately 1% of earth's. The field, while unequivocally intrinsic to the planet, may be due to remanent magnetization acquired from an extinct dynamo or a primordial magnetic field or due to a presently active dynamo. The latter possibility appears more plausible at present. In any case, the existence of the magnetic field provides very strong evidence of a mature differentiated planetary interior with a large core (core radius about 0.7 Mercury radius) and a record of the history of planetary formation in the magnetization of the crustal rocks.


Journal ArticleDOI
TL;DR: In this paper, the magnetic field behavior of a simple model for an amorphous ferromagnet with random single-ion anisotropy was considered. And the results indicated that the canted aligned state is always more stable than low-moment spinglass-like states.
Abstract: We consider the magnetic field behavior of a simple model for an amorphous ferromagnet with random single‐ion anisotropy. The spins are taken as classical unit vectors located at sites of a dense random packing model and coupled via nearest‐neighbor exchange interactions. An easy‐axis direction is chosen at random for each site. For large anisotropy, the coercivity is very large and the hysteresis curves resemble those found for amorphous TbFe2 at low temperature. As the anisotropy is reduced, there is a fairly abrupt change in the behavior of the model indicating that sufficiently weak random anisotropy is effectively averaged away. We have examined the energy of metastable states. The results indicate that the canted aligned state is always more stable than low‐moment spin‐glass‐like states. We also consider the magnetization process in the presence of imposed domain walls and find that wall motion is preceeded by magnetization rotation in the high‐coercivity regime.

BookDOI
01 Jan 1977
TL;DR: In this article, the upper critical field of Type-II superconductors has been investigated for anisotropic properties, and it has been shown that it exhibits anomalous properties at low temperatures.
Abstract: 1. The Upper Critical Field.- R-1 On the Theory of Macroscopic Anisotropy Phenomena in Type-II Superconductors.- R-2 Experimental Investigations on the Anisotropy of the Upper Critical Field in Type-II Superconductors.- 2. Hc2 and Related Properties.- C-1 The Influence of Fermi Surface Anisotropy on Hc2(T).- C-2 Impurity Dependence of Hc2 Anisotropy in Niobium.- C-3 Microscopic Anisotropy Parameters of Niobium.- C-4 Anisotropy of Hc2 in PbTl-Alloys.- C-5 Comments on Hc2 at Low Temperatures.- C-6 The Influence of Magnetic Anisotropy on the Properties of Niobium in the Mixed State.- C-7 Anisotropy of the Stress Dependence of Critical Parameters in Uniaxial Superconductors.- 3. Flux Lines.- R-3 Magnetization and Flux Line Lattice in Anisotropic Superconductors.- R-4 Morphology of Flux Line Lattices in Single-Crystalline Type-II Superconductors.- 4. Flux Lines, Domains and Magnetization.- C-8 Correlations between Flux Line Lattice and Crystal Lattice.- C-9 Experiments on the Correlation between the Flux Line Lattice and the Crystal Lattice in Superconducting Lead Films.- C-10 Anisotropy in the Intermediate State of Superconducting Mercury.- C-11 Mixed State Anisotropy of Superconducting Vanadium.- C-12 Measurement of Torque due to Anisotropy of the Magnetization Vector in Superconducting Niobium.- 5. Energy Gap.- R-5 Microscopic Calculations of Energy Gap Anisotropy.- R-6 An Evaluation of the Validity of Superconducting Evidence for Anisotropy and Multiple Energy Gaps.- 6. Energy Gap and Related Properties.- C-13 Tunneling Junction Phenomena: An Answer to Unanswered Questions.- C-14 An Analysis of Evidence for Superconducting Energy Gap and Pairing Interaction Anisotropy for Two Types of Experiments.- C-15 A Nearly Free Electron Model of the BCS Gap Equation: Energy Gap Anisotropy in Gallium.- C-16 Specific Heat of Superconducting Zinc.- 7. Other Topics.- C-17 Unusual Resistance Effect Shown in a Periodic S-N-S System (Pb-Sn Lamellar Eutectic).- C-18 The Upper Critical Field of Superconducting Polysulfur Nitride, (SN)x - (Abstract only).- List of Participants.- Author Index.

Journal ArticleDOI
G. Albanese1
TL;DR: In this article, a comparative discussion of the data obtained on M, Y, W and Z-type hexagonal ferrites is given, based on the Mossbauer, NMR and neutron spectroscopies, which allows to give more insight into correlations between the cation distribution, the sublattice magnetization and spin configuration.
Abstract: The application of the Mossbauer, NMR and neutron spectroscopies to the study of the hexagonal ferrites allows to give more insight into the correlations between the cation distribution, the sublattice magnetization and spin configuration. In the present paper a comparative discussion of the data obtained on M, Y, W and Z-type hexagonal ferrites is given.

Journal ArticleDOI
TL;DR: In this article, the effect of hydrogen absorption on the magnetic properties of CeFe 2 and ThFe 3 was studied by magnetization measurements and by the 57 Fe Mossbauer effect.