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Showing papers on "Ferromagnetism published in 1989"


Journal ArticleDOI
28 Mar 1989
TL;DR: Amorphous ribbons of composition Fe/sub 73.5,Cu/sub 1/Nb/sub 3/Si/sub 13.5/B/sub 9/ have been annealed above their crystallization temperature, which produces a homogeneous, ultrafine grain structure of alpha FeSi with typical grain diameters of 10-20 nm.
Abstract: Amorphous ribbons of composition Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 13.5/B/sub 9/ have been annealed above their crystallization temperature, which produces a homogeneous, ultrafine grain structure of alpha FeSi with typical grain diameters of 10-20 nm. The temperature dependence of saturation magnetization reveals two different magnetic phases which correspond to the alpha -FeSi grains and the grain boundary phase, respectively. The nanocrystalline material exhibits excellent soft magnetic properties which are discussed within the framework of the random anisotropy model. >

1,132 citations


Journal ArticleDOI
TL;DR: A perturbative theory of magnetocrystalline anisotropy and orbital moment in itinerant ferromagnets is presented and it is shown that it may produce an an isotropy in the magnetization of the order of 0.1\ensuremath{\mu}B per atom.
Abstract: A perturbative theory of magnetocrystalline anisotropy and orbital moment in itinerant ferromagnets is presented that clearly outlines the close connection between these two quantities. The theory is used to study the magnetocrystalline anisotropy in transition-metal monolayers. The importance of the crystal-field energy and of the filling of the valence band is emphasized. For the first time the orbital contribution to the magnetization in monolayers is estimated; it is shown that it may produce an anisotropy in the magnetization of the order of 0.1\ensuremath{\mu}B per atom.

980 citations


Journal ArticleDOI
TL;DR: In this paper, a fixed spin-moment procedure was used to study magnetovolume effects in bulk fcc iron and maganese, where the moments were constrained to have fixed values in a unit cell of two atoms to allow for antiferromagnetic and field-induced ferrimagnetic order.
Abstract: Total-energy band calculations, including an antiferromagnetic extension of the fixed-spin-moment procedure, are used to study magnetovolume effects in bulk fcc iron and maganese. By constraining these systems to have a fixed total magnetic moment in a single-atom fcc unit cell, we find magnetovolume instabilities in the form of first-order transitions from nonmagnetic to ferromagnetic behavior. Constraining the moments to have fixed values in a CuAu unit cell of two atoms to allow for antiferromagnetic (and field-induced ferrimagnetic) order alters these instabilities and yields second-order transitions from nonmagnetic to antiferromagnetic behavior at volumes coincident with the equilibrium volumes for both metals.

275 citations


Journal ArticleDOI
TL;DR: The magnetic ordering of a single crystal of the cubic polymorph of FeGe has been studied by small-angle neutron scattering as discussed by the authors, and the magnetic ordering in cubic FeGe is a Dzyaloshinskii spiral similar to the structure observed in the compound MnSi.
Abstract: The magnetic ordering of a single crystal of the cubic polymorph of FeGe has been studied by small-angle neutron scattering. The compound orders magnetically at TN=278.7 K into a long-range spiral (period approximately 683-700 AA) propagating along equivalent directions at high temperatures and along equivalent directions at low temperatures. The length of the spiral wavevector is nearly independent of temperature. The transition at TN is first order with very little hysteresis. The transition at which the direction of the spiral turns is rather sluggish. It takes place in a temperature interval of approximately 40 K and shows pronounced temperature hysteresis (T2 down arrow =211 K, T2 up arrow =245 K). Applied magnetic fields of 20-40 mT, depending on the temperature and the field direction, cause the spiral axis to turn into the direction of the applied field. As the field is further increased, the amplitude of the antiferromagnetic spiral decreases and the ferromagnetic component increases until at fields above approximately 200-300 mT cubic FeGe becomes magnetically saturated. The magnetic ordering in cubic FeGe is a Dzyaloshinskii spiral similar to the structure observed in the isostructural compound MnSi. However, in MnSi the spiral propagates along equivalent directions at all temperatures below TN=29.5 K.

246 citations



Journal ArticleDOI
16 Feb 1989-Nature
TL;DR: In this paper, the critical size for transformation from a uniform single-domain structure to a non-uniform three-dimensional structure is about 0.1 µm for magnetite.
Abstract: The fidelity of magnetic recording materials (whether they be synthetic crystals on a recording tape, or natural crystals in rocks recording changes in the Earth's magnetic field) depends on the uniformity of their magnetic structure. Such structure is determined by minimizing the energies arising from atomic magnetic dipole interactions. Previous micromagnetic models of coupled spin structures have contained well defined constraints to make the calculations tractable. By using a supercomputer, we have been able to perform unconstrained calculations of minimum energy structures for cubic assemblies of up to 22×22×22 exchange-coupled spins. The critical size for transformation from a uniform single-domain structure to a non-uniform three-dimensional structure is about 0.1 µm for magnetite, as found previously from one-dimensional modelling. However, a variety of different non-uniform structures are possible, with energies and magnetic moments much less than those of conventional lamellar domains. The predicted moments of unweighted combinations of these states agree well with experimental measurements on magnetite in the size range 0.08-0.5 μm. Surface spin structures are such as to minimize flux leakage out of the particle and might be misleadingly imaged by the Bitter colloid technique as indicating a single-domain state.

167 citations


Journal ArticleDOI
TL;DR: In this article, the magnetic properties of 3D transition metal monolayers on Pd(001) and Ag(001), as well as 3D dimers in Cu, Ag, and Pd, were investigated.
Abstract: We report results of systematic calculations for magnetic properties of 3d transition metal monolayers on Pd(001) and Ag(001). We find large similarities to interactions of magnetic 3d impurities in the bulk. Therefore the overlayer results are supplemented with results for 3d dimers in Cu, Ag, and Pd. Differences between the two classes of systems are utilized to reveal the interaction within the overlayers and between overlayers and substrates. In virtually all cases we find both ferromagnetic and antiferromagnetic solutions, showing large magnetic moments and similar densities of states. From the trend of the calculations we conclude that V, Cr, and Mn overlayers favor the antiferromagnetic c(2×2) structure, while Ti, Fe, Co, and Ni prefer the ferromagnetic one.

161 citations


Journal ArticleDOI
TL;DR: In this article, the magnetic properties of the chromium tellurides were analyzed and the Hall effect was used to show that the spin structure is not collinear ferromagnetic above Ts.
Abstract: Electronic band-structure calculations are presented for the ferromagnetic compounds CrTe, Cr3Te4 and Cr2Te4 and Cr2Te3. In these compounds the Cr3d-Te5p covalency and the Cr3d(z2)-Cr3d(z2)-overlap along the c axis are the most important interactions. The magnetic polarisation of Te is parallel to the Cr local moment in CrTe, antiparallel to it in Cr2Te3 and about zero in Cr2Te4. Measurements of electronic transport properties (resistivity, Hall effect and thermo-electric power) and magnetic properties of Cr1- delta Te( delta =0.1) and Cr3+xTe4(x=0.2) indicate that these chromium tellurides are p-type metals, with strong interaction between the holes in the Te5p band and the Cr magnetic moments. In the literature the variation of the magnetic properties of Cr3.2Te4 near Ts approximately=100 K has been attributed to a change from a canted antiferromagnetic to a collinear ferromagnetic structure. However, our Hall-effect measurements indicate that the spin structure is not collinear ferromagnetic above Ts.

150 citations


Journal ArticleDOI
TL;DR: In this article, the electronic structures of Co 2 NbSn and Ni 2 MnGa for both cubic and tetragonal structures were calculated by KKR method. And they showed that the band Jahn-Teller effect caused the lattice transformation in both alloys.
Abstract: It is known experimentally that Heusler alloys, Ni 2 MnGa and Co 2 NbSn undergo the cubic-to-tetragonal lattice transformation, in a ferromagnetic state and a paramagnetic one, respectively. We calculated electronic structures of Co 2 NbSn and Ni 2 MnGa for both cubic and tetragonal structures by KKR method. Comparing the density-of-state of the cubic and tetragonal structures for each alloy, it is expected that the band Jahn-Teller effect cause the lattice transformation in both alloys.

133 citations


Journal ArticleDOI
TL;DR: In this paper, low-field magnetic measurements reveal that both compounds undergo a magnetic phase transition at 8.1 and 8.6 K for I and II, respectively, indicating that the transition is ferromagnetic.
Abstract: The antiferromagnetic coupling constant has been estimated to be on the order of 260 cm −1 for both compounds. Low-field magnetic measurements reveal that both compounds undergo a magnetic phase transition at 8.1 and 8.6 K for I and II, respectively. The magnetization curves indicate that the transition is ferromagnetic. The magnetic anisotropy, which is of the Ising type, is originated mainly by the dipolar interaction between manganese and radical. The EPR spectra at room temperature do not show the typical behavior of one-dimensional systems due to the fact that the chains are not linear but zigzag; however, effects due to short-range order are visible in the EPR resonance fields on lowering the temperature

121 citations


Journal ArticleDOI
TL;DR: In this paper, a series of stable adducts of lanthanides with nitronyl nitroxides of general formula 0 were synthesized and the magnetic properties of the adduct were investigated in the range 11-300 K.
Abstract: 1H-imidazolyl-1-oxy1 3-oxide, NITR; R = phenyl, ethyl) The magnetic properties of Gd(hfac),(NITPh), were investigated in the range 11-300 K, while all the other compounds were studied in the range 4-300 K The gadolinium(II1) ions were found to be weakly coupled in a ferromagnetic fashion to the radical, while the radicals are antiferromagnetically coupled to each other The possible mechanisms responsible for this behavior are discussed Many efforts have currently been devoted to the synthesis of materials with expected magnetic properties In order to arrive at such a result, chemists must have available different building blocks with which it will be possible to arrange complex architectures Therefore, it is of fundamental interest to know the conditions under which, for instance, ferro- or antiferromagnetic coupling will be developed between different spins, and simple molecular clusters need to be synthesized and investigated in order to test theories This procedure is now fairly well established for transition-metal ions:*3 but much less is known for lanthanide ions Indeed, although lanthanides have long been known to develop interesting magnetic properties when used to dope transition-metal ionic the study of discrete magnetically coupled molecular systems has been largely overlooked up to the present Some of us have recently reported the magnetic properties of trinuclear complexes containing one gadolinium(II1) and two copper(I1) ions magnetically coupled in such a fashion that a smooth increase of XT on lowering T was observede12 These data were explained with an isotropic ferromagnetic exchange between the gadolinium and the copper ions The coupling must be determined by superexchange through the oxygen bridges, but no attempt was made to use an orbital model to justify the observed coupling This purpose in principle might be achieved more easily by studying the interaction of lanthanide ions with stable organic radicals such as nitroxides, because in this case the magnetic interaction would be of the direct exchange type, and the observed coupling might be directly connected with the nature of the bond interaction between the x* orbital on the ligand and the f orbitals of the lanthanides In other words, the nitroxides, which are widely used as spin labels and spin probes, in this case might be used as bond probes,13 in the sense that an analysis of their interaction with the metal ions should provide first-hand information on the metal-ligand bond and on the nature of the magnetic orbitals With these considerations in mind, we synthesized a series of stable adducts of lanthanides with nitronyl nitroxides of general formula 0

Journal ArticleDOI
TL;DR: It is shown that small changes in the layering pattern can lead to large changes in /ital M/(/ital T/) and static susceptibility and change in the value of the interface exchange parameter cause large changes only in the weak-coupling limit.
Abstract: Magnetic superlattices composed of ferromagnetic films (Fe and Gd) which couple antiferromagnetically at the interfaces are studied. In a magnetic field a variety of different spin configurations are possible. We show how these phases are reflected in magnetization and susceptibility measurements. In particular, a twisted spin configuration is characterized by a much larger susceptibility than an aligned spin configuration. We show that small changes in the layering pattern can lead to large changes in /ital M/(/ital T/) and static susceptibility. In contrast, changes in the value of the interface exchange parameter cause large changes only in the weak-coupling limit.

Journal ArticleDOI
TL;DR: In this article, the crystal structure and magnetic properties of inter-metallic compounds XMnSb (X=Pt, Ni, Co, Au, Cu) and PtMnSn were investigated and it was found that several of these materials contain precipitates of other phases and/or large atomic disorder.
Abstract: The authors present investigations of the crystal structure the microstructure and the magnetic properties of the inter-metallic compounds XMnSb (X=Pt, Ni, Co, Au, Cu) and PtMnSn. It was found that several of these materials contain precipitates of other phases and/or large atomic disorder, which can be influenced by heat treatment. The magnetic properties show an effective paramagnetic moment which differs from the value corresponding to the saturation moment at 0 K. This effect is attributed to a decrease of the conduction electron spin polarisation at high temperature.

Journal ArticleDOI
TL;DR: Comparaison quantitative entre l'orientation de l'aimantation mesuree dans les parois de domaines en surface and les previsions de the theorie micromagnetique.
Abstract: The magnetization orientations in domain walls at the surfaces of an Fe crystal, a ferromagnetic glass, and a Permalloy film, measured by scanning electron microscopy with polarization analysis, exhibit asymmetric surface N\'eel wall profiles which (1) are at least twice as wide as interior Bloch walls in bulk and (2) are described quantitatively by our micromagnetic calculations without assuming any special surface parameters. Misinterpretation of domain-wall widths, Bitter patterns, and magnetic-force-microscopy images can result from overlooking the extreme effect of the surface on magnetic microstructure.

Journal ArticleDOI
TL;DR: Three different spin arrangements for the (001) surface of Cr are discussed on the basis of self-consistent total-energy calculations: ferromagnetism, inside-the-surface $c(2\ifmmode\times\else\texttimes\fi{}2)$ antiferromag Netism, and "topological" antiferroelectricity between ferromagnetic terraces separated by single steps.
Abstract: Three different spin arrangements for the (001) surface of Cr are discussed on the basis of self-consistent total-energy calculations: ferromagnetism, inside-the-surface $c(2\ifmmode\times\else\texttimes\fi{}2)$ antiferromagnetism, and "topological" antiferromagnetism between ferromagnetic terraces separated by single steps. The $c(2\ifmmode\times\else\texttimes\fi{}2)$ antiferromagnetic configuration is found to be energetically unfavorable. Instead, topological antiferromagnetism is compatible with both the absence of magnetization observed by spin-resolved photoemission and the existence of spin-split surface states detected by energy- and angular-resolved photoemission.

Journal ArticleDOI
TL;DR: In this paper, the spatial distribution of local magnetic anisotropy axes is characterized by the correlation function C ( x ) which reflects a short-range structural order in a solid.

Journal ArticleDOI
TL;DR: For the first time the full temperature dependence of the quasiparticle band structure and the quAsiparticle density of states of ferromagnetic Ni are presented.
Abstract: By use of a generalized Hubbard model, we investigate the influence of electron correlations on the temperature dependence of the quasiparticle properties of ferromagnetic Ni. The one-particle energies of the model Hamiltonian are taken from a realistic band-structure calculation. The model contains only two parameters, Hubbard U and the interband exchange J. It is approximately solved by use of a self-consistent moment method. We find a ferromagnetic ground state, mainly caused by the uppermost d subband, a magnetic moment at T=0 of 0.56${\ensuremath{\mu}}_{B}$, a Curie temperature of ${T}_{C}$=635 K, a Brillouin-type magnetization curve, a strict Curie-Weiss behavior of the paramagnetic susceptibility, a satellite peak some 6 eV below the chemical potential \ensuremath{\mu} as a consequence of strong electron correlations in the uppermost d subband, a temperature-dependent spin polarization of the satellite (\ensuremath{\simeq}75% at T=0), temperature-dependent exchange splittings at the top of the d band (0.23--0.36 eV at T=0), and an enhancement factor of the electronic specific heat q(T=0) \ensuremath{\simeq}-0.56. All these results are in excellent agreement with the experiment. For the first time the full temperature dependence of the quasiparticle band structure and the quasiparticle density of states of ferromagnetic Ni are presented.

Journal ArticleDOI
TL;DR: A review of the magnetocaloric effect (MCE) in rare-earth magnetic materials of different classes is given in this paper, where the results of measurements of the MCE near phase transitions are given for the vicinity of the Curie and Ne?l temperatures, and also near magnetic compensation points in the case of ferromagnetic-helicoidal antiferromagnetism-ferromagnetic phase transitions.
Abstract: A review is given of the experimental investigations of the magnetocaloric effect (MCE) in rare-earth magnetic materials of different classes: heavy rare-earth metals and their alloys, iron garnets, and intermetallic compounds. The results of measurements of the MCE near phase transitions are given for the vicinity of the Curie and Ne?l temperatures, and also near magnetic compensation points in the case of ferromagnetism-helicoidal antiferromagnetism and helicoidal ferromagnetism?paramagnetism transitions. The contributions to the MCE made by the various magnetic sublattices in rare-earth ferromagnets are identified. Measurements of the MCE in single crystals of alloys of heavy rare-earth metals have made it possible to identify the main energy contributions to the helicoidal antiferromagnetism-ferromagnetism phase transitions and their energy dependences. The concluding section of the review deals with the technical applications of the MCE exhibited by rare-earth magnetic materials. An analysis is made of the potential applications as refrigerants in magnetic refrigerators, in thermodynamic cycles, and in structures of various types.

Journal ArticleDOI
TL;DR: A combination of ac susceptibility, dc magnetization in a variety of applied fields, and electrical resistivity data is reported for five members of the R 2 Mo 2 O 7 series of cubic pyrochlore structure oxides, R = Nd, Sm, Gd, Tb, and Y.

Journal ArticleDOI
TL;DR: Conversion-electron Mossbauer spectroscopy of ultrathin pure Fe-based films on W(110) coated by Ag provides detailed information on the mode of growth, the film structure, and the local structure of magnetic order, in particular its thermal decrease.
Abstract: Conversion-electron M\"ossbauer spectroscopy of ultrathin pure $^{57}\mathrm{Fe}$(110) films on W(110) coated by Ag provides detailed information on the mode of growth, the film structure, and the local structure of magnetic order, in particular its thermal decrease, because different structural components are marked by strongly differing magnetic hyperfine fields.

Journal ArticleDOI
TL;DR: Magnetic and magnetoelectric measurements were made on a single crystal of ferroelectric PbFe0.5Nb0.3 in this paper, and it was revealed that the magnetic class below and above T m c was determined to be m' and ml', respectively.
Abstract: Magnetic and magnetoelectric measurements were made on a single crystal of ferroelectric PbFe0.5Nb0.5O3. It was revealed that PbFe0.5Nb0.5O3 has a weak ferromagnetic moment and linear magnetoelectric effect below a transition point T m c of approximately 9 K. The magnetic class below and above T m c was determined to be m' and ml', respectively. A possible model of the transition which explains this symmetry change is proposed.

Journal ArticleDOI
TL;DR: In this paper, the growth of thin films of fcc cobalt on Cu(100) has been characterized with medium energy electron diffraction (MEED) and thermal energy atom scattering (TEAS) in order to prepare films of reproducible structural perfection, interdiffusion profile and atomic concentration.

Journal ArticleDOI
S. H. Lu1, J. Quinn1, D. Tian1, F. Jona1, P. M. Marcus2 
TL;DR: In this article, a tetragonally distorted face-centered-cubic (fcc) structure with a 3.61 A, c= 3.54 A and 4-expanded first interlayer spacing was found.

Journal ArticleDOI
Markus Donath1
TL;DR: Inverse photoemission (IPE) with spin-polarized electrons provides a way to measure separately the exchange-split majority and minority bands in ferromagnets above the Fermi level as discussed by the authors.
Abstract: Inverse photoemission (IPE) with spin-polarized electrons provides a way to measure separately the exchange-split majority and minority bands in ferromagnets above the Fermi level. Consequently spin-resolved IPE turns out to be an outstanding technique for obtaining information on surface magnetism: the magnetization of the topmost atomic layer may be investigated by measuring the exchange splitting of electronic states that are localized within the surface layer. Theoretical models of ferromagnetism may be tested by observing the temperature behavior of bands which contribute to the ferromagnetism of the material. The magnetic coupling of an adsorbate to the ferromagnetic substrate may be studied by probing adsorbate-induced bands. Results for the Ni(110) surface serve as an illustration to discuss the status of spin-resolved IPE and its application to the field of surface magnetism.

Journal ArticleDOI
TL;DR: In this article, the results of X-ray scattering studies of the rare earth metals and related new results for superlattices and thin slabs were reviewed and discussed in the context of lattice modulations.
Abstract: We review the results of X-ray scattering studies of the rare earth metals and present related new results for superlattices and thin slabs. In rare earth crystals we have observed weak structural modulations which accompany the magnetic ordering. The wave length of this modulation can be derived from a spin-slip model in accordance with symmetry considerations. X-ray scattering of both the charge and magnetization density modulations allow for highly accurate determination of the magnetic wave vector. The physical basis of our discussion is given in the context of lattice modulations. The implications of these results for the understanding of magnetic structure of rare earth superlattices are also discussed in the light of recent neutron diffraction studies of holmium-yttrium superlattices. The effect of the finite size of the magnetic block in a superlattice is considered and it is shown that significantly different behavior than in bulk is expected. In particular it is found that for thin slabs the ferromagnetic phase has the lowest energy.

Journal ArticleDOI
TL;DR: In this paper, the Stoner theory of itinerant ferromagnetism was used to calculate the energy and magnetic moments of homogeneous bcc-fcc lattice deformation in iron.
Abstract: The energetics of homogeneous bcc-fcc lattice deformation in iron at 0 K has been investigated along the tetragonal ``Bain'' deformation path. The total energy (as a function of volume), the enthalpy (as a function of pressure), the pressure-volume relations---both for nonmagnetic (NM) and ferromagnetic (FM) states---were calculated using the linear muffin-tin-orbital (LMTO) method. The ground-state magnetic properties (ferromagnetic contributions to the total energy and magnetic moments) were found by making use of the Stoner theory of itinerant ferromagnetism, rather than spin-polarized calculations. This circumvents the difficulties of using the traditional local-spin-density approximation which fails to describe correctly the energetics of iron phases. The Stoner exchange parameter I was calculated from the linear-response theory for each axial ratio c/a as a function of volume and then adjusted by a constant enhancement factor \ensuremath{\beta}, determined by fitting the equilibrium atomic volume of the FM bcc phase. No other adjustments of any quantities were performed. The calculations revealed a somewhat unusual behavior of enthalpy along the deformation path.The enthalpy of the NM phase exhibits a monotonic decrease with c/a, the bcc modification being unstable with respect to the shear deformation. Moreover, up to a certain c/a (depending on pressure), the NM bcc phase is also unstable with respect to spontaneous magnetization. Ferromagnetism stabilizes the bcc phase. However, the FM fcc phase is unstable with respect to shear deformation. The enthalphy curve along the deformation path then has a cusp corresponding to a first-order phase transition between FM and NM states accompanied by an appreciable volume discontinuity. For the FM bcc, the calculated bulk modulus (1.689 mbar) and the magnetic moment (2.223${\ensuremath{\mu}}_{B}$/atom) as well as the fcc-bcc enthalpy difference at zero pressure (6.947 kJ/mol) are in good agreement with available experimental data. A fcc-bcc lattice-deformation enthalpy barrier at the equilibrium pressure ${P}_{0}$=145 kbar is found to be 12.762 kJ/mol. The NM fcc lattice loses mechanical stability at a fcc-bcc enthalpy difference of -14.072 kJ/mol. As an aid to the development of improved interatomic potentials for iron, plots of FM contributions to the energy versus Wigner-Seitz radius for different c/a are also presented.

Journal ArticleDOI
TL;DR: On montre que certains elements non diagonaux de la matrice de l'interaction de Coulomb entre electrons de Bloch, jouent un role fondamental dans le ferromagnetisme metallique.
Abstract: It is pointed out that certain off-diagonal matrix elements of the Coulomb interaction between Bloch electrons are likely to play a fundamental role in metallic ferromagnetism. These matrix elements lower the energy when the two interacting electrons are in states of opposite bonding character, thus favoring a situation where up and down electron bands have different fillings. It is proposed that this effect can explain the occurrence of metallic ferromagnetism in solids, without band degeneracy playing an essential role.

Journal ArticleDOI
TL;DR: Observations of magnetic aftereffect in ferromagnetic films of a few atomic layers of a large interface anisotropy and square hysteresis loop are made using the recently developed alternating-gradient magnetometer.
Abstract: By using the recently developed alternating-gradient magnetometer, that combines very high sensitivity and measurement rapidity, we have made observations of magnetic aftereffect in ferromagnetic films of a few atomic layers. These CO films have a perpendicular easy axis due to a large interface anisotropy and square hysteresis loop. The study of the field dependence of the relaxation rate gives information on the activation energy. The results are discussed in connection with the possible existence of domains and wall motion. It is well known, after Ndel,' that magnetic aftereffect due to thermal activation is a general property of all ferromagnetic materials. In bulk materials, the time scale for magnetic aftereffect is often so large that aftereffect cannot be observed. On the other hand, when the dimensions are very small, aftereffect becomes very important (small particles, rock magnetism). One can therefore ' raise the question of whether aftereffect can be observed when one dimension only is very small, i.e., in ultrathin films.

Journal ArticleDOI
TL;DR: In this article, the spin wave spectra of exchange-coupled epitaxial double-layers of bcc ferromagnetic material with the (100) and (110) surfaces were analyzed theoretically within the classical continuum model.