Showing papers on "Ferromagnetism published in 1983"
TL;DR: The band structure of Mn-based Heusler alloys of the crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method.
Abstract: The band structure of Mn-based Heusler alloys of the $C{1}_{b}$ crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method. Some of these magnetic compounds show unusual electronic properties. The majority-spin electrons are metallic, whereas the minority-spin electrons are semiconducting.
3,851 citations
TL;DR: In this article, the magneto-optical Kerr rotation in more than 200 metallic systems comprising alloys as well as intermetallic compounds of 3D transition metals was studied and the saturation moment at 4.2 K was determined.
686 citations
TL;DR: In this paper, the temperature dependence of the magnetic hyperfine field of microcrystalline goethite has been studied in detail and the results have been compared to the behaviour of well-crystallized Goethite.
315 citations
TL;DR: In this paper, the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices were presented, showing that the apparent dipolar interactions between the spheres may be made attractive or repulsive.
Abstract: Holes are produced inside a thin layer of magnetic fluid with use of monodisperse polystyrene spheres with diameters in the micrometer range. With an external magnetic field an apparent magnetic dipole will be associated with each hole as a result of the displaced fluid. The apparent dipolar interactions between the spheres may be made attractive or repulsive. This Letter presents the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices.
289 citations
TL;DR: In this paper, the magnetic properties of the cubic NaZn 13 type pseudobinary compounds La(T x Si 1-x ) 13 were studied for T = Fe, Co and Ni in the temperature range 4.2-300 K.
206 citations
TL;DR: In this paper, the stabilization potential of domain walls is determined for both reversible and irreversible after-effects of amorphous alloys using first-order reaction kinetics.
Abstract: The magnetic after-effect spectrum of amorphous alloys is attributed to rearrangements of defect structures which are described by two-level systems. Using first-order reaction kinetics, the so-called stabilization potential of domain walls is determined for both ‘reversible’ and ‘irreversible’ after-effects. It is shown that by an appropriate averaging over the energy gap parameters and the activation energies, the relaxation phenomena in amorphous alloys can be described explicitly.
159 citations
TL;DR: In this article, a series of self-consistent band calculations have been performed for a ferromagnetic state of iron in both the bcc and fcc structures, and the dependence of the magnetic moment per atom on the lattice parameter was obtained.
Abstract: A series of self-consistent-band calculations have been performed for a ferromagnetic state of iron in both the bcc and fcc structures. The dependence of the magnetic moment per atom on the lattice parameter was obtained. The linear combination of Gaussian orbitals method was employed in conjunction with a local-density exchange-correlation potential. An explanation is given for the abrupt increase in the magnetic moment in the fcc case near ${r}_{s}=2.7$ in terms of behavior of the band structure.
152 citations
Patent•
14 Jul 1983
TL;DR: In this article, the authors proposed a method to provide ferromagnetic and great magnetizing force without heating a substrate at high temperature when a magnetic layer is formed in gaseous phase by a method wherein a continuous thin magnetic layer composed of Al, B, Mn is formed on the substrate.
Abstract: PURPOSE:To provide ferromagnetic and great coercive force without heating a substrate at high temperature when a magnetic layer is formed in gaseous phase by a method wherein a continuous thin magnetic layer composed of Al, B, Mn is formed on the substrate CONSTITUTION:It is so arranged that a magnetic layer of a magnetic recording medium is composed of 15-398wt% Al, 02-5wt% B, and Mn substantially as the remainder In this case, a further preferred result will be obtained if the magnetic layer is caused to consist of 17-348wt% Al, 02-3wt% B and the remaining 65-78wt% Mn Moreover, as a substrate on which such a magnetic layer is formed, a non-magnetic high polymer, glass, ceramic, or alloy may be used In so doing, it is possible to provide ferromagnetic and great magnetizing force without the formation in gaseous phase while heating the substrate or adding a heating process after the formation
143 citations
TL;DR: An intercalated 2H-type layer compound, Cr 1/3 NbS 2, was investigated by magnetic and neutron diffraction measurements as mentioned in this paper, and it was found that this compound is a helimagnet with a very long period along the c-axis and with the spins in the c -plane.
Abstract: An intercalated 2H-type layer compound, Cr 1/3 NbS 2 , was investigated by magnetic and neutron diffraction measurements. It was found that this compound is a helimagnet with a very long period along the c -axis and with the spins in the c -plane. The magnetic behavior is similar to that of an easy-plane type ferromagnet except for the magnetization curve in the c -plane. The Curie temperature is 127 K. The saturation magnetization corresponds to 2.9 µ B /Cr. The uniaxial anisotropy constant, K 1 , is -1.46×10 6 ergs/cc at 4.2 K. The magnetizatiom curve in the c -plane shows a metamagnetic behavior, the critical field of which is as low as 1.5 kOe except near T c . Small angle scattering measurements showed a helical structure with Q =0.013 A -1 (480 A period). The helical spin structure and the metamagnetism is explained as due to the antisymmetric exchange interaction.
143 citations
TL;DR: In this article, the authors show that the superlattice formation for approximately a half-filled band is like a Peierls transition, but it results from the electronic structure as a whole with no special role attached to the Fermi surface.
Abstract: The metals in the middle of the transition metal series have a tendency towards antiferromagnetism, ordered AB alloy structures and lattice distortions based on a twofold superlattice. By contrast, at the beginning and end of the series the corresponding tendency is towards ferromagnetism, chemical segregation rather than alloy formation, and stable simple structures. The authors show how all these results can be understood in a unified way in terms of a general theorem published earlier. The argument applies quite generally to any set of tight-binding bands such as the d bands, independent of the specific structure. In a general sense the superlattice formation for approximately a half-filled band is like a Peierls transition, but it results from the electronic structure as a whole with no special role attached to the Fermi surface. The case of threefold superlattices is also discussed with examples.
139 citations
IBM1
TL;DR: The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt; discontinuities in the magnetization, magnetostriction and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity as mentioned in this paper.
Abstract: The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt. For Pt contents between 32 and 40 at%, discontinuities in the magnetization, magnetostriction, and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity. The structure of films containing about 25 at% Pt is a mixture of hexagonal and face-centered cubic (FCC) phases. At this composition the magnetostriction is small, but coercivities are large-700 to 2000 Oe-and dependent upon film thickness. The coercivities of these films do not change with heat treatment up to temperatures of 600°C but decrease markedly at 700°C. The properties of equiatomic Co-Pt film s are similar to those of bulk alloys. In particular the large coercivity observed in films after heal treatment at 500° to 700°C is due to the formation of an ordered tetragonal phase within the face-centered cubic matrix. The structure of films of about 75 at% Pt is initially a disordered face-centered cubic phase and with heat treatment beginning at 500°C an ordered face-centered cubic phase forms. The coercivity of these films (∼200 Oe) does not change with annealing at 500°C. It decreases slightly upon further annealing at 600°C to 700°C. Electron microscope observations were used to correlate the magnetic properties with film structure.
TL;DR: The magnetic phase diagram for CrFe alloys was determined by neutron scattering and low-field magnetisation as discussed by the authors, and two critical concentrations were found as the state of magnetic order evolved from itinerant antiferromagnetism for Fe concentrations less than cA=16.0+or-0.5% to ferromagnetic long-range order.
Abstract: For pt.I see ibid., vol.13, p.441 (1983). The magnetic phase diagram for CrFe alloys was determined by neutron scattering and low-field magnetisation. Two critical concentrations were found as the state of magnetic order evolved from itinerant antiferromagnetism for Fe concentrations less than cA=16.0+or-0.5% to ferromagnetism for Fe concentrations greater than cF=19.0+or-0.5%. Spin-glass behaviour was observed between the two critical concentrations. The onset of ferromagnetism was studied by neutron small-angle scattering. Analysis of the concentration and temperature dependence of the magnetic correlation range below cF suggested that a geometrical element is involved in the development of ferromagnetic long-range order; these results were in semi-quantitative agreement with models for the percolation multi-critical point. The bulk magnetic properties of alloys between the two critical concentrations were consistent with a simple fine magnetic particle model of percolation clusters of Fe moments fluctuating against barriers arising from magnetostatic shape anisotropy.
TL;DR: In this article, the authors carried out elastic and inelastic neutron scattering experiments on a MnSi single crystal with the use of a neutron polarized-beam technique, and observed a characteristic polarization dependence in the magnetic Bragg reflections of the spiral phase, as well as the spin-wave excitations and the critical scattering near ${T}_{c}$.
Abstract: MnSi is a cubic ferromagnet with a long-wavelength spiral below its Curie temperature at 29 K. Recent theoretical and experimental studies have shown that this spiral is only right handed because of the lack of a center of symmetry in the Mn atomic arrangement. We have carried out elastic and inelastic neutron scattering experiments on a MnSi single crystal with the use of a neutron polarized-beam technique. A characteristic polarization dependence was observed in the magnetic Bragg reflections of the spiral phase, as well as the spin-wave excitations and the critical scattering near ${T}_{c}$. This polarization dependence persists into the ferromagnetic phase under a magnetic field and also at temperatures as high as 150 K.
TL;DR: In this paper, the first order magnetic phase transition from ferromagnetic to antiferromagnetic state has been observed with increasing temperature in the Ta concentration range in itinerant electron magnets.
Abstract: Magnetic phase transitions in itinerant electron magnets Hf 1- x Ta x Fe 2 have been studied from measurements of Mossbauer effect, magnetization and X-ray diffraction The first order magnetic phase transition from ferromagnetic to antiferromagnetic state has been observed with increasing temperature in the Ta concentration range 01< x <03 It is concluded that the magnetic phase transitions in Hf 1- x Ta x Fe 2 can be interpreted in terms of the recent theoretical result by Moriya and Usami on magnetic phase transitions in itinerant electron systems
TL;DR: In this paper, a phenomenological model for amorphous magnets with ferromagnetic exchange and small random anisotropy is proposed, and a new type of spin-glass state is described.
Abstract: The phenomenological model is proposed for amorphous magnets with ferromagnetic exchange and small random anisotropy. A new type of spin-glass state is described. Its behaviour in an external magnetic field is shown to deviate strongly from mean-field theory predictions. The effect of coherent anisotropy is discussed.
TL;DR: In this article, the magnetization measurements performed in the temperature range 4.2-300 K in fields up to 15 kOe on amorphous Fe 90 Zr 10, Co 90Zr 10, and Ni 90ZR 10 alloys, prepared by the single-roller-quenching technique, are presented.
Abstract: Results of the magnetization measurements performed in the temperature range 4.2-300 K in fields up to 15 kOe on amorphous Fe 90 Zr 10 , Co 90 Zr 10 , and Ni 90 Zr 10 alloys, prepared by the single-roller-quenching technique, are presented. While the glassy Co 90 Zr 10 and Ni 90 Zr 10 alloys at low fields show a normal ferromagnetic behavior down to 4.2 K, amorphous Fe 90 Zr 10 exhibits a transition from the ferromagnetic state to the mictomagnetic state at a temperature Tf which lies well below the ferromagnetic ordering temperature. T f decreases linearly with increasing H up to fields H-250 Oe and this linear dependence on H gives T f (H=0)=40± 1 K. The magnetic behavior at high fields and the temperature dependence of spontaneous magnetization can be satisfactorily accounted for in terms of a theory proposed for weak itinerant ferromagnets. The unusually large value of the high-field susceptibility at 4.2 K observed for Fe 90 Zr 10 , in particular, is found to contain, besides the contribution arising due to the Invar characteristics of this alloy, a contribution typical of that observed in mictomagnetic alloys. Finally, from an appraisal of the present results and those previously reported on glassy Fe 90 Zr 10 , it is concluded that this alloy contains two types of magnetic electrons: those possessing itinerant character and giving rise to ferromagnetism (single-particle contribution) and Invar anomalies, and those having localized nature and responsible for both the ferromagnetic (spin-wave contribution) and the mictomagnetic behavior.
TL;DR: Magnetization and Mossbauer studies of RFe5Al7(R = Y, Sm to Lu, ThMn12 crystal structure) in magnetic fields up to 50 kOe and temperatures 4.1 to 500 K have been performed as discussed by the authors.
TL;DR: In this article, the results of recent experiments on magnetic properties of ferromagnetic 3D metal surfaces and thin films are compared with each other and with theoretical predictions, including electron spin polarization data Mossbauer and SQUID measurements of thin Fe films.
TL;DR: In this paper, a magnetic study has been carried out in the temperature range 1.2-25 K and magnetic field range 0 to 50 kOe on single crystals of manganese (II) phthalocyanine.
Abstract: : A magnetic study has been carried out in the temperature range 1.2-25 K and magnetic field range 0 to 50 kOe on single crystals of manganese (II) phthalocyanine. At higher temperatures the magnetic properties of manganese (II) phthalocyanine exhibit chain-like characteristics which may be understood in terms of ferromagnetic Heisenberg intrachain exchange of S = 3/2 ions with a weak antiferromagnetic interchain interaction. In the ordered state, Tc, = 8.3 K, MnPc is a canted ferromagnet with easy axes of magnetization being along X1 and X3 directions. A zero-field splitting of the single ion 4A2 state of the manganese (II) ion gives rise to canted ferromagnetism which does not show complete saturation at the high field range of these experiments (50 kOe). The spin structure of manganese (II) phthalocyanine at low temperature is discussed. (Author)
TL;DR: In this article, the authors presented accurate self-consistent local spin density electronic structure calculations for linear chains of Ni and Fe atoms which realistically treat three-dimensional nature, and found that the d-d effective exchange interaction is similar to that in bulk.
TL;DR: In this article, the high temperature phase of the Ni2MnSn Heusler alloy is obtained directly from the melt (structure of B2 type) and the same magneton number n′ eff ⋍ 5 per Mn atom results.
TL;DR: In this article, the transverse and longitudinal magnetic susceptibility of ferromagnetic metals were derived from density-functional theory in the local density approximation, and made practical for computation through a transformation from a Fourier representation to an orbital representation.
Abstract: Expressions for the transverse and longitudinal magnetic (spin) susceptibility of ferromagnetic metals, which have been derived from density-functional theory in the local-density approximation, are simplified and made practical for computation through a transformation from a Fourier representation to an orbital representation. The method is applied to a calculation of the transverse susceptibility of ferromagnetic nickel at $T=0$. Results are obtained for spin-wave energies and widths using a semiempirical band structure.
TL;DR: The physical picture of Invar and Heusler alloys provided by parameter-free, self-consistent, spin-polarized energy-band calculations is described in this paper.
TL;DR: In this paper, the magnetic phase transition in materials with exchange disorder (amorphous ferromagnets, spin glasses) is discussed and a molecular field theory with correlations in space and time is developed, which relates deviations from the mean field behavior to the interplay between the temperature dependent thermal correlations in the spin system and the spatial fluctuations of the material.
01 Dec 1983
TL;DR: In this paper, an active magnetic regenerator is described along with the method of calculation and the temperature profiles for a normal regenerator and a magnetic regenerative refrigerator are shown, and the theory of these devices is predicted by solving the partial differential equations that describe fluid and the magnetic solid.
Abstract: The adiabatic temperature change with field which is limited to about 2 K/Tesla for ferromagnets near their Curie temperatures by the change of magnetization with temperature and the lattice heat capacity is discussed. Practical magnetic refrigerators operate on a regenerative cycle such as the Brayton cycle. This cycle can be executed through the use of an active magnetic regenerator, i.e., a regenerator composed of magnetic material that is cycled in an out of a magnetic field with appropriate fluid flows. The theory of these devices is predicted by solving the partial differential equations that describe fluid and the magnetic solid. The active magnetic regenerator is described along with the method of calculation. Temperature profiles for a normal regenerator and a magnetic regenerative refrigerator are shown.
TL;DR: The magnetic structure and weak ferromagnetism of Mn3Ge was studied by polarized neutron diffraction in this paper, and the magnetic structure was determined to have a triangular spin configuration in the c-plane with the symmetry reversed to the crystalline symmetry.
TL;DR: In this paper, low field dc magnetization measurements on (FexMn1−x)75P16B6Al3 alloys at 4 ⪅ T ⫅ 300 K were reported.
TL;DR: In this paper, the α-ThSi 2 type CeSi x (155≤ x ≤ 200) was investigated and the system undergoes a nonmagnetic-magnetic transition at around x =183 Magnetic and thermal properties of the system suggest that this is the first example of a ferromagnetic dense Kondo system.
TL;DR: In this article, the results of a series of neutron small-angle scattering measurements on ferromagnetic CrFe alloys close to the critical concentration for ferromagnetism (cF) have been analyzed to yield the concentration and temperature dependence of the magnetic inverse correlation range, kappa 1(c,T).
Abstract: For pt.II see ibid., vol.13, p.451 (1983). The results of a series of neutron small-angle scattering measurements on ferromagnetic CrFe alloys close to the critical concentration for ferromagnetism (cF) have been analysed to yield the concentration and temperature dependence of the magnetic inverse correlation range, kappa 1(c,T). It is found that kappa 1 does not go to zero at Tc, but varies as (c-cF)((T-TC)/TC)nu + kappa R where nu =1.2+or-0.1. At low temperatures the alloys showed significant long-range inhomogeneity in the ferromagnetic correlations; this became more pronounced as the concentration approached cF. These features are discussed in relation to the other complex magnetic properties of these highly disordered ferromagnets.
TL;DR: In this paper, a two-dimensional Heisenberg spin system with ferromagnetic exchange, local random anisotropy, and coherent anisotropic anisophotonicity was studied in two dimensions.