Showing papers on "Ferromagnetism published in 1981"
TL;DR: The phase diagram of the infinite-range model of spin-glasses exhibits two mixed phases as mentioned in this paper, where ferromagnetism and spin-glass order coexist, due to freezing of the transverse degrees of freedom.
Abstract: The phase diagram of the infinite-range model of spin-glasses exhibits two mixed phases. In these mixed phases, ferromagnetism and spin-glass order coexist, due to freezing of the transverse degrees of freedom or replica symmetry breaking. This may help to interpret a number of recent experimental findings, e.g., in $\mathrm{Au}\mathrm{Fe}$.
731 citations
TL;DR: In this paper, the lattice constants of these compounds were determined and the formation of the Heusler L 2 1 -type phase was compared with model predictions, and it was found that only a limited number of these combinations leads to the cubic L2 1 -Heusler-type compounds.
359 citations
TL;DR: The many theoretical studies of the various magnetic, thermal and magnetoelastic properties for paramagnetic and ferromagnetic transition metals and alloys in the simple itinerant electron model are reviewed in this article.
Abstract: The many theoretical studies of the various magnetic, thermal and magnetoelastic properties for paramagnetic and ferromagnetic transition metals and alloys in the simple itinerant electron model are reviewed. The important amendments to the simple itinerant electron model or Stoner model of magnetism due to the spin wave excitations and spin fluctuations are explained.
260 citations
TL;DR: In this paper, the magnetic entropy of a typical 3-dimensional ferromagnetic substance near the Curie temperature as a function of temperature and magnetic field strength was calculated and compared with the experimental results.
250 citations
TL;DR: In this article, the two-impurity Kondo problem is studied by using perturbative scaling techniques and the physics are determined by the interplay between the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the two impurity spins and the Kondo effect.
Abstract: The two-impurity Kondo problem is studied by use of perturbative scaling techniques. The physics is determined by the interplay between the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the two impurity spins and the Kondo effect. In particular, for a strong ferromagnetic RKKY interaction the susceptibility exhibits three structures as the temperature is lowered, corresponding to the ferromagnetic locking together of the two impurity spins followed by a two-stage freezing out of their local moments by the conduction electrons due to the Kondo effect.
213 citations
IBM1
TL;DR: In this article, the authors systematically investigated exchange coupled films of sputter deposited Ni80Fe20/FeMn and FeMn/Ni 80Fe20 and obtained films with high exchange bias and low coercive forces.
Abstract: We have systematically investigated exchange coupled films of sputter deposited Ni80Fe20/FeMn and FeMn/Ni80Fe20 and obtained films with high exchange bias and low coercive forces. The variation of film properties with deposition conditions as well as with the permalloy and FeMn thicknesses have also been studied. The results demonstrated a strong dependence of exchange bias effect (HUA) on the amount of γ‐phase FeMn, the amount of impurities, as well as the abruptness of the transition profile at the interface. In addition, our results have also raised a number of new questions concerning the magnetic state of the interface and the origin of the interface coupling phenomena.
187 citations
TL;DR: HAL as discussed by the authors is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Two-dimensional ising model with competing interactions : floating phase, walls and dislocations J. Villain, P. Bak
183 citations
TL;DR: In this paper, the effect of spin-density structure factor on the amplitude of X-rays scattered by a magnetically ordered substance, carried out in relativistic quantum theory (i.e., taking the spin into account), is detailed.
Abstract: The calculation of the amplitude of X-rays scattered by a magnetically ordered substance, carried out in the relativistic quantum theory (i.e. taking the spin into account), is detailed. The effect of the orbital momentum is described in an appendix. The practical formulae dealing with the polarization of the beams are given both in a simple form for the usual experiments and in a complete form, using the Stokes vectors, for the most general case. The experiments show a change in the intensity of the X-rays diffracted by a ferromagnetic (pure iron) or a ferrimagnetic (zinc-substituted magnetite) powder when the magnetization, perpendicular to the diffraction plane, is reversed. The relative values of these intensity changes range from 10-4 to 5 x 10-3 and agree in sign and magnitude with the predictions. They are proportional to the spin-density structure factor multiplied by the imaginary part of the charge- density structure factor; the large anomalous scattering of the Cu Kα radiation in the iron-containing samples is used in the present experiments.
165 citations
TL;DR: Magnetic moments and total energies of ferromagnetic and antiferromagnetic bcc and fcc iron are obtained as a function of atomic volume by means of self-consistent band-structure calculations using the local spin-density-functional approximation as discussed by the authors.
148 citations
TL;DR: A detailed analysis of experimental results on the basis of the theory of micromagnetism for inhomogeneous systems shows clearly that the ferromagnetic phase transition is mainly influenced by intrinsic exchange fluctuations whereas the characteristic properties of the magnetization curve are governed predominantely by defect structures as mentioned in this paper.
Abstract: In amorphous ferromagnetic alloys the characteristic properties of magnetization processes and of the hysteresis loop are sensitively influenced by fluctuations of material properties and defect structures. A detailed analysis of experimental results on the basis of the theory of micromagnetism for inhomogeneous systems shows clearly that the ferromagnetic phase transition is mainly influenced by intrinsic exchange fluctuations whereas the characteristic properties of the magnetization curve are governed predominantely by defect structures. The defect structures are identified as agglomerates of the free volume which are formed during the rapid quenching process.
132 citations
TL;DR: In this article, the free energy of a superconductor containing a periodic array of magnetic ions with ferromagnetic interactions was calculated for the various phases possible in a super-conductor.
Abstract: The free energy is calculated for the various phases possible in a superconductor containing a periodic array of magnetic ions with ferromagnetic interactions. Suggestions are made for experimental observation of coexisting superconductivity and long-range magnetic order.
01 Jun 1981
TL;DR: In this paper, a trigonal effective crystal-field model was used to explain the anisotropy of the susceptibility and magnetization of a clinochlore crystal using the trigonal effect model for 1:1 and 2:1 layer silicates, with a splitting of the Tzg triplet of 1,120 K.
Abstract: Magnetization, susceptibility and M6ssbauer spectra are reported for representative chlorite samples with differing iron content. The anisotropy of the susceptibility and magnetization of a clinochlore crystal is explained using the trigonal effective crystal-field model developed earlier for 1:1 and 2:1 layer silicates, with a splitting of the Tzg triplet of 1,120 K. Predominant exchange interactions in the iron-rich samples are ferromagnetic with J= 1.2 K, as for other trioctahedral ferrous minerals. A peak in the sus- ceptibility of thuringite occurs at Tm = 5.5 K, and magnetic hyperfine splitting appears at lower temperatures in the M6ssbauer spectrum. However neutron diffraction reveals no long-range magnetic order in thuringite (or biotite, which behaves similarly). The only magnetic contribution to the diffraction pattern at 1.6 K is increased small angle scattering (q<0.4~ 1). A factor favouring this random ferromagnetic ground state over the planar antiferromag- netic state of greenalite and minnesotaite is the presence of pairs of ferric ions on adjacent sites, in conjunction with magnetic vacancies in the octahedral sheets. Monte Carlo simulations of the magnetic ground state of the sheets illus- trate how long range ferromagnetic order may be destroyed by vortices forming around the Fe 3 +--Fe 3 + pairs. tral in chlorites. Substitution of trivalent ions for Mg in the brucite layers is compensated by replacement of Si by A1 in the tetrahedral sheets of the talc layers (Bailey 1980). The general formula for a trioctahedral chlorite is
TL;DR: In this article, it was confirmed that the value of Curie (or Neel) temperature for the Mn sublattice decreases with increasing c constant and that the remaining compounds have antiferromagnetic properties.
TL;DR: In this article, the first moment of the magnetic disturbances at the surface of a ferromagnet was determined using neutrons reflected from the surface, with a sensitivity corresponding to one magnetic dead layer.
Abstract: Polarized neutrons reflected from the surface of a ferromagnet are sensitive to the magnetization close to the surface as well as to the bulk magnetization. In a calculation using parameters appropriate to nickel it is shown how the two contributions can be separated. Neutron measurements can determine the first moment of the magnetic disturbances at the surface, with a sensitivity corresponding to one magnetic dead layer.
TL;DR: In this paper, a high-temperature itinerant ferromagnet CeRh3B2 was reported to order magnetically at 115K. The magnetic ordering seems to be intrinsic and presumably arises from the Rh d-band.
Abstract: Reports a high-temperature itinerant ferromagnet CeRh3B2 which orders magnetically at 115K. The magnetic ordering seems to be intrinsic and presumably arises from the Rh d-band. Similar compounds of La, Pr and Nd do not show any magnetic ordering down to 77K.
TL;DR: The magnetic properties of amorphous yttrium-iron alloys Y1-xFex have been studied over a wide concentration range 0.2-0.4 as mentioned in this paper.
Abstract: The magnetic properties of amorphous yttrium-iron alloys Y1-xFex have been studied over a wide concentration range 0.32
TL;DR: In this article, the authors report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni and show the moment per Ni atom is reduced relative to pure Ni.
Abstract: We report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni, which, contrary to earlier ferromagnetic resonance measurements, show the moment per Ni atom is reduced relative to pure Ni. The low‐temperature magnetization is found to vary linearly with modulation amplitude, but, surprisingly, the Curie temperature is found to be almost amplitude independent.
TL;DR: In this article, the ac hysteresis loop and susceptibility of amorphous alloys were measured in the presence of small constant fields and it was shown that the ac susceptibility of alloys with w just above w C has maxima near both transition temperatures.
TL;DR: In this article, the coercive field of magnetostrictive amorphous ferromagnetic alloys is determined by four types of interactions: volume pinning by stress sources, intrinsic fluctuations of material properties, surface irregularities, and relaxation phenomena.
Abstract: Magnetic properties of the hysteresis loop of magnetostrictive amorphous ferromagnetic alloys are predominantly determined by the magnetoelastic coupling energy between the spontaneous magnetization and internal stresses. Domain structures as well as the pinning of domain walls are governed by long-range and short-range stresses, respectively. As sources of elastic stresses we have detected quasidislocation dipoles exerting stress fields which vary as 1/r2. The coercive field is shown to be determined by four types of interactions : 1) volume pinning by stress sources; 2) intrinsic fluctuations of material properties; 3) surface irregularities; 4) relaxation phenomena.
TL;DR: A thorough review of the main advances concerning both linear and nonlinear wave propagations in magnetizable deformable solids is presented in this paper, where the main features such as the influence of strong bias magnetic fields and the introduction of small parameters which bring corrections to classical results of elasticity theory are systematically investigated.
TL;DR: In this paper, the development of magnetic order in the region of the reentrant superconducting transition in Ho${\mathrm{Mo}}_{6}$${S}}_{8} was investigated.
Abstract: Neutron scattering has been used to investigate the development of magnetic order in the region of the reentrant superconducting transition in Ho${\mathrm{Mo}}_{6}$${\mathrm{S}}_{8}$. On cooling, an ordered oscillatory magnetic state develops in the superconducting phase, with a wavelength which increases with the application of a magnetic field. On further cooling the sample reverts to the normal conducting state as ferromagnetism sets in. No oscillatory magnetic phase is observed, however, when the superconducting phase is approached from low temperatures.
TL;DR: In this article, X-ray, neutron diffraction and magnetometric measurements were performed on four intermetallics, and they were found to be antiferromagnetic with Neel points at 368, 380, 460 and 395 K respectively.
TL;DR: In this paper, the authors consider whether a state of disordered local moments (DLM) can exist in an itinerant magnetic metal above Tc and develop a criterion Il(EF)>1 for the non-magnetic state to be unstable with respect to the formation of DLM.
Abstract: The authors consider whether a state of disordered local moments (DLM) can exist in an itinerant magnetic metal above Tc. They develop a criterion Il(EF)>1 for the non-magnetic state to be unstable with respect to the formation of DLM. This criterion is more easily satisfied than the Stoner criterion for ferromagnetism. In(EF)>1, near the centre of a tight-binding band and less easily satisfied near the band edges. They report calculations on tight-binding d bands of 3d transition metals by means of the recursion method. These suggest that BCC Mn and Fe do possess a DLM state, whilst Cr, FCC Mn and Ni do not. They present a method of calculation of the real part of the Green function by the recursion method.
TL;DR: The magnetic behavior of TiBe2 is found to be similar to that of strongly enhanced paramagnets like Pd and Ni3Ga as discussed by the authors, which might be due to the electron-electron interaction.
TL;DR: In this paper, the Sine-Gordon chain was shown to be a topologically stable excitation in one-dimensional magnetic chains with different symmetries and pulse modes with continuously varying amplitudes are found to exist.
Abstract: We review recent theoretical results on nonlinear excitations in one‐dimensional magnets. We deal with classical magnetic chains in a continuum description and discuss solutions to the full nonlinear equations of motion for ferromagnetic as well as antiferromagnetic exchange and additional single ion anisotropies and external magnetic fields. Easy‐plane ferro‐ and antiferromagnetic chains in an external field breaking the easy‐plane symmetry can be mapped approximately to the Sine‐Gordon chain. We introduce this mapping and discuss the approximation involved. The kink modes of the Sine‐Gordon chain are topologically stable excitations in these magnetic chains whereas in 1d magnets with different symmetries also pulse modes with continuously varying amplitudes are found to exist. We investigate the influence of nonlinear excitations on dynamic correlation functions in Sine‐Gordon‐like magnetic chains at finite temperatures. Kinks lead to a characteristic broadening of Bragg peaks in antiferromagnets and to a central peak in the dynamic response function of the xy ferromagnet. The latter is shown to be modified considerably by the lowest order corrections to the noninteracting kink/magnon approach.
TL;DR: In the case of R Fe 6 Al 6 (R = Y, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb), the magnetization curves start with low values at low temperatures and rise to very high values at T max ~ 230 K and then drop to 0 at T c ~ 330 K as discussed by the authors.
TL;DR: The magnetic susceptibility of RB2C2 has been measured in the temperature range of 3-300 K and Curie-Weiss fits to the susceptibilities led to effective moments in agreement with those expected for R3+ ions as mentioned in this paper.
TL;DR: In this paper, the authors derived the FMR conditions from total free energy expressions, where the differences between magnetization direction and applied field direction were taken into consideration, and obtained the three best fitting parameters of K 1, K u, δ and γ.