Showing papers on "Single domain published in 1974"
TL;DR: In this article, the magnetic properties of iron-garnet films and the use of these films as film-waveguide optical switches were discussed, and a detailed investigation of the switching process between 0 and 300 MHz was performed.
Abstract: We discuss magnetic properties of iron‐garnet films and the use of these films as film‐waveguide optical switches. Our experimental study involves the observation of magnetic domains, measurements of Faraday rotation constants, coercive forces and anisotropy fields, and a detailed investigation of the switching process between 0 and 300 MHz. Our theoretical study includes magneto‐optics in film waveguides, and analysis of the serpentine circuit, and an extensive calculation of the motion of the magnetization. For low driving fields, the process of optical switching is the formation of periodic domains and the subsequent motion of domain walls. For higher driving fields, the process is rotation of the magnetization in unison. The switching field required for 100% modulation is several times the anisotropy field in the film, which can be as small as 0.1 Oe.
58 citations
TL;DR: In this paper, the magnetite particles were given an anhysteretic remanent magnetization and then oxidized with a field perpendicular to the original remanence, and the results showed that shape anisotropy dominated any CRM growth or there is a positive exchange interaction between magnetite and magnetite.
Abstract: Excited oxygen gas has been used to oxidize single-domain magnetite particles at temperatures of 50° and 200°C. The magnetite particles were long thin submicron rods with a length to width ratio of 11:1. The samples were given an anhysteretic remanent magnetization and then oxidized with a field perpendicular to the original remanence. The samples were completely oxidized to maghemite and the intensity of initial remanence was reduced by 12%. No chemical remanent magnetization (CRM) was detected in any of the samples, the indication being that either shape anisotropy dominated any CRM growth or there is a positive exchange interaction between magnetite and maghemite.
57 citations
TL;DR: In this article, the magnetization and the related magnetocrystalline anisotropy in terms of a cubic crystalline electric field and an isotropic exchange interaction are described.
Abstract: Magnetization measurements are reported for single crystals of PrAl2 in the range from 4.2K to 30K for magnetic fields up to 150 kOe applied in the (100), (110) and (111) directions. For these measurements, together with the magnetization results obtained earlier for TbAl2 the authors give a quantitative quantum mechanical description of the magnetization and the related magnetocrystalline anisotropy in terms of a cubic crystalline electric field and an isotropic exchange interaction. The parameters used in this description can be unified to good approximation to all REAl2 intermetallic compounds where detailed experiments are available.
52 citations
TL;DR: In this paper, a method for computing the ferromagnetic properties of single-domain particles having cubic anisotropy was proposed for overcoming the indeterminacy of the magnetization orientation when magnetization reversal occurs.
Abstract: For calculations of the ferromagnetic properties of single-domain particles having cubic anisotropy, a computing method is outlined for overcoming the indeterminacy of the magnetization orientation when magnetization reversal occurs. This is used to calculate the magnetization and remanent magnetization loops of random arrays of such particles. It is found for such systems that h c = 0·189 and 0·321, and h R = 0·204 and 0·333 for K 0, respectively. The reduced super-paramagnetic transition temperature is 0–0417 for both cases. Comparisons are made between these calculations and the calculated properties of systems subject to uniaxial anisotropy.
48 citations
TL;DR: Stacey and Banerjee as discussed by the authors showed that the pseudo-single-domain (PSD) intensity and stability of multidomain magnetite grains 0.05-15 μm in size are attributed to residual magnetic moments not removed by demagnetization.
45 citations
TL;DR: In this article, single domain particles of Fe alloys (Fe versus Ni, Cu, Si, Cr, Gd and Ho) were prepared by the evaporation method and the saturation magnetization, remanent magnetization and coercive force of these particles were measured by an automatic magnetic balance.
Abstract: Single domain particles of Fe alloys (Fe versus Ni, Cu, Si, Cr, Gd and Ho) were prepared by the evaporation method. The saturation magnetization, remanent magnetization and coercive force of these particles were measured by an automatic magnetic balance. The dispersion of the anisotropy of Fe, Co and Ni particles were determined by a torque meter. The characteristics of these alloy particles were discussed in terms of their applicability to industrial use. The stability for oxydation and the magnetic orientation of particles have already been reported in the previous paper of this series. By choosing a suitable composition of alloys, the coercivity of the prepared particles can be controlled in the range of 200 to 1800 Oe. It was found that the anisotropy dispersion of Fe-Ni alloy was smaller than that of a commercial CrO2 tape.
41 citations
TL;DR: The reflectivity of single domain crystals of LiNbO 3 and KNbO3 has been measured using linearly polarized light up to 10 eV as mentioned in this paper, and the Kramers-Kronig analysis reveals a large anisotropy of the optical constants in the interband transition region.
37 citations
TL;DR: In this paper, the properties of Gd-Co sputtered films are discussed not only for bubble domain but also for thermomagnetic application, and the temperature dependence of the M-H loop is studied.
Abstract: Stripe domains and bubble domains are observed in Gd-Co sputtered films. The domain patterns are different from one another for different preparation conditions. In this paper, preparation conditions and some properties of Gd-Co films, namely the domain pattern observed by the polar Kerr magneto-optic effect and the M-H loops measured by the Kerr and the Hall effect, are reported. The temperature dependence of the M-H loop is studied about the compensation temperature. The properties of Gd-Co sputtered films are discussed not only for bubble domain but also for thermomagnetic application.
31 citations
TL;DR: In this paper, the motion of a domain wall surrounded by a perturbed region of current density resulting from the action of the magnetic field of the domain on a uniform impressed current density was investigated.
Abstract: Calculations are made for the motion of a domain wall surrounded by a perturbed region of current density resulting from the action of the magnetic field of the domain on a uniform impressed current density The perturbed region follows the motion of the domain wall and produces a magnetic field which causes the domain to propagate In particular, a ferromagnetic layer containing a cylindrical domain, with a Hall‐effect overlayer, is considered
31 citations
TL;DR: In this paper, the elastic compliance coefficients, dielectric permittivities and piezoelectric constants of a BaTiO3 tetragonal crystal with periodically alternating layers of 180° domains were calculated.
Abstract: The elastic compliance coefficients, dielectric permittivities and piezoelectric constants of a BaTiO3 tetragonal crystal with periodically alternating layers of 180° domains were calculated. It was shown that the presence of 180° domain walls resulted in changes of a number of elastic and dielectric constants of the polydomain sample as compared with the single domain one. The propagation of elastic waves in the laminated crystal was considered. The frequency dependence of effective permittivity and the effect of domain structure on the piezoelectric behaviour of crystal were analysed.
30 citations
TL;DR: In this paper, the magnetic domain structures of regularly shaped samples of FeBO3 have been studied using the Faraday effect and simple strip domain structures induced by magnetostriction were used to determine domain wall widths and domain wall mobility.
Abstract: The magnetic domain structures of regularly shaped samples of FeBO3 have been studied using the Faraday effect. Simple strip domain structures, induced by magnetostriction, were used to determine domain wall widths and domain wall mobility. A comparison of measured and calculated domain wall widths reveals a disparity of two orders of magnitude. This is explained in terms of a complex wall structure at the intersection of Neel and Bloch walls. The sources of large scatter obtained in the mobility results are discussed, and an alternative method of measurement is suggested. It is shown that the relaxation mechanism present in the mobility measurements is not that producing the ferromagnetic resonance linewidth.
TL;DR: In this article, the preparation of glasses in the CoO-Fe2O3-B2O4 system is described and it is shown that the magnetic spinel cobalt ferrite can be obtained in precipitate when the glasses are heat-treated.
Abstract: The preparation of glasses in the CoO-Fe2O3-B2O3 system is described and it is shown that the magnetic spinel cobalt ferrite (CoFe2O4) can be obtained in precipitate when the glasses are heat-treated. The identity of the crystalline phase is established by means of Mossbauer spectroscopy. It is shown that the magnetic properties of the glass-ceramics can be controlled by means of the heat-treatment schedule and intrinsic coercivities as high as 1900 Oe are recorded. The magnetic properties of the as-cast and heat-treated material are discussed generally in terms of superparamagnetic, single domain and multi-domain behaviour. The highest values of the intrinsic coercivity and remanence are compared to those calculated for an assembly of non-interacting single domain particles with positive cubic magnetocrystalline anisotropy.
TL;DR: In this article, the motion of domain walls induced by microwave pulses is described in high power phase shifters using ferrite toroids, and it is shown that a circularly polarized rf magnetic field of strength h o exerts substantially the same pressure on domain walls as a dc magnetic field applied along the domain axis.
Abstract: A new high power effect in ferrites, the motion of domain walls induced by microwave pulses is described. In high power phase shifters using ferrite toroids this effect can change the remanent magnetization and hence change the insertion phase of the device. A theoretical explanation of these effects is obtained by considering a partially magnetized ferrite material having uniaxial anisotropy and exposed to an rf magnetic field perpendicular to the anisotropy axis. Experiments at 3 GHz on a twin-slab (i.e., toroid) phase shifter at peak power levels up to 300 kW are in good agreement with the theoretical expectations. It is shown that a circularly polarized rf magnetic field of strength h o exerts substantially the same pressure on domain walls as a dc magnetic field applied along the domain axis and having the strength H_{z} = \gammah\min{o}\max{2}\omega w, where γ is the gyromagnetic ratio and ω the angular frequency. The rf generated pressure tends to shrink those domains in which the imposed sense of circular polarization coincides with the sense of the natural spin precession.
TL;DR: In this article, the low temperature field dependent magnetization and susceptibility of the linear ferromagnet CsNiF 3 were compared with calculations for a one-dimensional classical spin field model.
TL;DR: In this article, the micromagnetics of competition between magnetostatic and exchange energies are investigated for two geometries. For a cylindrical tube an approximate solution yields the magnetization for all values of the applied magnetic field producing remanence, a coercive field and a critical field at which the magnetisation changes irreversibly.
Abstract: The micromagnetics of competition between magnetostatic and exchange energies is investigated for two geometries. For a cylindrical tube an approximate solution yields the magnetization for all values of the applied magnetic field producing remanence, a coercive field and a critical field at which the magnetization changes irreversibly. The behavior in the irreversible region is also calculated. For the geometry of a thin toroidal shell it is found that most of the reversal processes is divergentless, but in a crucial region magnetic charges develop.
TL;DR: In this paper, it was shown that the magnetization and specific heat of amorphous magnets can be expressed in terms of averages of the magnetisation and specific Heat of small domains in which the spins are assumed to be alike.
TL;DR: The coercive field H c of single domain particles is stress sensitive as mentioned in this paper, and it is possible to orient selectively the orientation of magnetic particles in an arbitrary volume element of volume L3- at position \overrightarrow{r} in a sample.
Abstract: The coercive field H c of single domain particles is stress sensitive. Theory shows that stress alone leads to H c (stress) = 3λ s σ/I s in a uniaxial single domain particle, if the magnetization rotates coherently. λ s is the magnetostriction, σ the stress, and I s the magnetization. It is therefore possible to orient selectively the orientation of magnetic particles in an arbitrary volume element of volume L3- at position \overrightarrow{r} in a sample, since by the proper superposition of ultrasonic pulses with pulse width L a higher stress state can be generated at \overrightarrow{r} than in any other section of the sample. This set of pulses will reduce H c from the unstressed state to H' c c . An applied field H with H' c c will line up dipoles parallel to H only in this volume elemet. One can "write" into the memory. Since this "line up" leads to a signal in coil surrounding the sample, one can also "read" if the dipole orientation changes in the volume L3, since this leads to an induced voltage in the coil surrounding the sample.
TL;DR: In this paper, the effect of longitudinal tensile stress and dc bias fields on the domain patterns and power loss of polycrystalline specimens of commercial 3% grain-oriented silicon-iron under longitudinal and transverse ac magnetization and rotational flux conditions was investigated.
Abstract: Measurements of power loss have been made on individual grains in polycrystalline specimens of commercial 3% grain-oriented silicon-iron under longitudinal and transverse ac magnetization and rotational flux conditions. The domain configurations have also been observed using a stroboscopic Kerr magnetic-optic apparatus. The effect of longitudinal stress and dc bias fields on the domain patterns and power loss under these ac magnetization conditions has also been investigated. It can be concluded that the highest power loss occurs under pure rotational flux conditions and that the application of longitudinal compressive stress increases the power loss, but to a lesser extent when a transverse ac flux is present. The application of a longitudinal dc field increases the power loss for all ac magnetizing conditions, and it has been observed that a longitudinal tensile stress has the opposite effect on the domain configuration to the application of a transverse dc field.
IBM1
TL;DR: In this article, the authors measured the in-plane magnetization and the perpendicular magnetization which 10-μm-thick tape of γ-Fe 2 O 3 particles acquires on passing through the field of a head driven with direct current.
Abstract: We have measured the in-plane magnetization and the perpendicular magnetization which 10-μm-thick tape of γ-Fe 2 O 3 particles acquires on passing through the field of a head driven with direct current. The perpendicular component of the head field has two adverse effects on the remanent state at the surface of the tape closest to the head. First, it induces a perpendicular component of magnetization which leads to asymmetry in the output pulse. Second, it leads to a reduction in the in-plane magnetization which reduces the signal output level at high recording densities. The perpendicular moment can be ≥5% of the in-plane moment in the normal writing current range of the head. In the same current range the reduction in in-plane moment represents about 5% of the tape's maximum remanent moment.
TL;DR: In this paper, it was shown that magnetic domains tend to move parallel with the current in a nearby conductor; the motion is due to Hall currents set up in the conductor by the domain field and is independent of any field gradients due to the unperturbed current.
Abstract: It was recently pointed out that magnetic domains tend to move parallel with the current in a nearby conductor; the motion is due to Hall currents set up in the conductor by the domain field and is independent of any field gradients due to the unperturbed current. The magnitude of the force that produces this drift is here calculated for the cases of a single straight domain wall and of a circular magnetic bubble. The force is found to be strong enough to produce controlled motion of a magnetic bubble, provided that the magnetic material is optically flat and the current carriers in the conductor have a high mobility.
TL;DR: In this paper, it was shown that critical size estimates may be more reliable if they are deduced from magnetic studies on pure magnetite samples containing a narrow range of particle sizes rather than on those with some cation deficiency and a large size variation, as were used by Dunlop.
Abstract: Cation deficient (CD) magnetite phases may show peculiar hysteresis properties, as was inferred from recent experiments. Dunlop's estimate of superparamagnetic to single-domain threshold sizes for CD magnetite from hysteresis measurements may thus be misleading. Also critical size estimates may be more reliable if they are deduced from magnetic studies on pure magnetite samples containing a narrow range of particle sizes rather than on those with some cation deficiency and a large size variation, as were used by Dunlop.
TL;DR: In this article, the influence of the coercive force, H c, on domain growth in MnBi films is investigated on a local scale, and it is found that for domain tip movement to occur, a critical domain width has to be exceeded.
Abstract: The influence of the coercive force, H c , on domain growth in MnBi films is investigated on a local scale. It is found that for domain tip movement to occur, a critical domain width has to be exceeded. When H c is in the same order of magnitude of the magnetostatic pressures, this critical width is restored in the final stripe domain width, which is considerably greater than the equilibrium domain width in the absence of H c .
TL;DR: In this paper, an analysis of the effect of stress on spike or closure domains formed at pores is presented in an effort to gain further insight into the effects of applied stress on remanence ratios.
Abstract: An analysis of the effect of stress on spike or closure domains formed at pores is presented in an effort to gain further insight into the effects of applied stress on remanence ratios. The model is based on the concept that spike domain volume is dependent on the domain wall energy, which in turn is influenced by magnetic anisotropy and stress energies. The results indicate that the effects on remanence ratios are proportional to p /K_{1} , the ratio of the product of porosity and average magnetostriction constant to the magnitude of the first-order magnetocrystalline anisotropy constant. This conclusion is used in conjunction with the results of previous models to offer an explanation of the effects of applied stress in the Y 3 Mn x Fe 5-x O 12 system.
TL;DR: In this article, the authors made a calculation of the force that acts on a cylindrical bubble domain when a current flows in a thin adjacent sheet of a magnetoresistive material such as Permalloy.
Abstract: An electric current in a conductor can move a nearby magnetic domain even when all magnetic field gradients due to the current are canceled out; the motion comes from perturbations that are induced in the current by the domain field. A calculation is here made of the force that acts on a cylindrical bubble domain when a current flows in a thin adjacent sheet of a magnetoresistive material such as Permalloy. When the Permalloy layer is magnetized in its own plane, the direction of the force relative to the current depends on the direction of magnetization; the force can be rotated through 360° by rotating the magnetization through 180°. The greatest driving force possible is a few milligauss for each A/cm in the conducting layer.
TL;DR: In this article, it was shown that the magnetic hyperfine field at the Fe nuclei-B n, determined by Mossbauer measurements, decreases faster with Ni content than the spontaneous magnetization.
Abstract: Ferromagnetic domain structures of (110) disks. It is shown that near the 30 per cent Ni concentration, the magnetic hyperfine field at the Fe nuclei-B n , determined by Mossbauer measurements, decreases faster with Ni content than the spontaneous magnetization. Using theoretical results about the origin of B n , this effect can be explained by considering the dependence of the lattice parameter on the Ni content.
TL;DR: The critical fields for the nucleation and reversal of magnetisation in thin films leading to the formation of strip and bubble domain structures have been calculated in this paper, where attention has been paid to the role of imperfections which have been represented by a local lowering of the anisotropy constant.
Abstract: The critical fields for the nucleation and reversal of magnetisation in thin films leading to the formation of strip and bubble domain structures have been calculated. Attention has been paid to the role of imperfections which have been represented by a local lowering of the anisotropy constant. The value of the anisotropy constant and the size of the imperfections have been shown to be important and the corresponding fields compared with other important field values in bubble domain theory.
TL;DR: In this paper, the influence of in-plane magnetic fields and stresses on the magnetization position was measured and the observed variation was interpreted in the light of a simple theory involving anisotropy, magnetostriction and magnetostatic energies.
Abstract: Magnetic domain structure in epitaxial YIG films was investigated using Faraday effect and Bitter method. These experiments have shown complex structures of closure domains. The influence of in-plane magnetic fields and stresses on the magnetization position was measured. The observed variation was interpreted in the light of a simple theory involving anisotropy, magnetostriction and magnetostatic energies. A new determination of the induced stress was inferred from this study, X-ray experiments were also performed. Interfacial dislocations have been observed which are consistent with the rather small value found for the stress.
TL;DR: In this article, the magnetization of a V 3 Ga superconducting tape between two successive flux jumps has been experimentally determined by means of search coil measurement in an increasing field perpendicular to the surface.