Showing papers on "Saturation (magnetic) published in 1990"
TL;DR: In this paper, it was shown that the volume ratio of Fe16N2 in the Fe-N films increases with decreasing Fe•N film thickness, and the maximum value for Bs is 2.66 T.
Abstract: Fe‐N films with thicknesses of 70–1000 A were deposited by MBE onto Fe films which were epitaxially grown onto GaAs(100) substrates. Without the Fe layer, epitaxially grown Fe‐N films could not be obtained due to a reaction between Fe‐N and GaAs. TEM observations and x‐ray diffraction patterns showed that the epitaxially grown Fe‐N films consist of Fe16N2 and Fe, and that crystal orientation is Fe16N2 (001)//Fe(110). It was found that the saturation magnetic flux density (Bs) increases as the thickness of the Fe‐N films decreases. This is because the volume ratio of Fe16N2 in the Fe‐N films increases with decreasing Fe‐N film thickness. The maximum value for Bs is 2.66 T, and the volume ratio is 85%. These results indicate that Fe16N2 has a high saturation magnetic flux density of 2.8–3.0 T.
222 citations
TL;DR: In this article, the magnetic cross relaxation was studied in a coupled two-spin population system and the magnetic exchange or cross relaxation between the protein and the solvent rather than the chemical exchange of exchangeable protons on the protein.
197 citations
IBM1
TL;DR: In this article, the tip-apex domain is found to be oriented along the tip axis, because of shape anisotropy, and the stray field emerging from the tip apex is comparable to the size of the tip saturation field.
Abstract: Magnetic force microscopy is a new method for imaging ferromagnetic domains with a high lateral resolution (10 nm). In this paper we give the basic tip parameters that have to be taken into account to achieve a quantitative image interpretation. For the electrochemically otched polycrystalline iron, nickel and cobalt wires, the tip-apex domain is found to be oriented along the tip axis, because of shape anisotropy. The stray field emerging from the tip apex is comparable to the size of the tip saturation field. The effective domain lengthL determines the image formation: the force due to magnetization patterns of scales which are large compared toL follow the point-dipole approximation. In the opposite case, a single-pole model is more appropriate. While a cobalt tip can be treated as an isolated domain, for nickel and iron a net polarization in the tip wire induced by the front apex-domain has to be considered. A new analytical theory provides an overall understanding of the image formation and allows the determination of the magnetic field vector and the estimation of its magnitude from measurements.
115 citations
TL;DR: In this article, the crystal structure of Li2CuO2 has been investigated and its magnetic structure solved by neutron powder diffraction, and the magnetic moment of copper atoms at 1.5 K is 0.96(4)microB, which is very close to the saturation moment of spin only Cu+2 (d9).
108 citations
TL;DR: In this paper, a method of separation of ferrimagnetic and paramagnetic components of magnetic anisotropy from the total anisotropic component is developed. But this method is not suitable for the case of high-frequency measurements.
Abstract: SUMMARY A method of separation of ferrimagnetic and paramagnetic components of magnetic anisotropy from the total anisotropy is developed. From the anisotropy measurement of a specimen in a low field (susceptibility anisotropy) and from measurement in two high fields stronger than the saturation field of the ferrimagnetic fraction present, the following anisotropy components can be calculated: susceptibility anisotropy (field-independent) of the paramagnetic fraction, low-field (susceptibility) anisotropy of the ferrimagnetic fraction and high-field anisotropy of the ferrimagnetic fraction. Errors possibly arising from imperfect saturation of the ferrimagnetic fraction in the field practically available are analysed.
98 citations
TL;DR: In this paper, the authors obtained iron nitride films with a saturation magnetization of 21 kG, coercivity less than 1 Oe, and hard axis permeability of 4000.
Abstract: We have obtained iron nitride films with a saturation magnetization of 21 kG, coercivity less than 1 Oe, and hard axis permeability of 4000. The saturation magnetostriction decreased as input power increased, or as the N2/Ar flow rate ratio decreased. X‐ray analysis revealed that an increase in input power or a decrease in the flow rate ratio resulted in less γ’‐Fe4N phase in the films deposited. The coercivity was also very sensitive to these variations. The iron nitride films did not show structural changes under vacuum annealing from 150 to 300 °C, but their coercivity decreased slightly. The coercivity increased rapidly after annealing above 350 °C, however.
87 citations
17 Apr 1990
TL;DR: In this paper, an empirical description of stress-induced magnetization is presented as a practical extension of the Jiles-Atherton model of ferromagnetic hysteresis.
Abstract: It is argued that attempts to describe the stress magnetization behavior of ferromagnetic materials have, in general, relied upon unsubstantiated assumptions regarding the distribution of domains and the relative motion of domain walls under the combined influences of applied field and mechanical stress. An empirical description of stress-induced magnetization is presented as a practical extension of the Jiles-Atherton model of ferromagnetic hysteresis. It permits a semiquantitative description of the stress magnetization characteristics of ferromagnetic materials and highlights the profound influence of previous magnetic history. It is concluded that measuring the B/H characteristics of a material as a function of stress and invoking the Jiles-Atherton theory of ferromagnetism could provide a computational basis for predicting the magnetic behavior of complex structures under mechanical stress. >
66 citations
TL;DR: In this article, a thermal fluctuation analysis of high-temperature coercive force data suggests that regions 200-250 nm in size are thermally activated as a unit in grains of all sizes; these are likely domain walls.
Abstract: Approximately equidimensional magnetite crystals, with mean sizes of 215, 390, and 540 nm, respectively, have been produced by reducing hematite crystals. Isothermal magnetic hysteresis properties show a clear progression toward multidomain-like behavior as the mean grain size increases. Saturation remanences Mrs are only 5–10% of saturation magnetization Ms, coercive forces HC are low (5.5–8 mT), and both Mrs and HC have grain-size dependences compatible with those previously established for smaller and larger hydrothermally produced magnetites. Coercivities during remanence acquisition are greater than those measured during demagnetization. The difference between acquisition and destructive fields increases in the larger grains as a result of the increasing importance of the internal demagnetizing field. The low-temperature transition is well expressed in the Mrs and HC data of the 540-nm sample but is more subdued for smaller grains. Magnetostrictive, magnetocrystalline, and magnetostatic mechanisms in turn govern coercivity as the temperature rises. Remanence and coercivity ratios, Mrs/Ms and HR/HC, are almost temperature independent up to 500°C, indicating that domain wall configurations resulting from saturating fields are about the same at any temperature. A thermal fluctuation analysis of high-temperature coercive force data suggests that regions 200–250 nm in size are thermally activated as a unit in grains of all sizes; these are likely domain walls. Apparent demagnetizing factors calculated from both low- and high-temperature data are consistent with a mixture of two-domain (2D) and three-domain (3D) grains in all samples. However, theories of remanence in conventional 2D and 3D grains or in mixtures of 2D, 3D, and metastable single-domain grains do not explain the data in a satisfying way.
59 citations
TL;DR: In this article, the heavy hole excitation saturation intensity in GaAs/AlGaAs quantum wells was measured as a function of applied electric field and AlGaAs barrier design, and the saturation intensity increased with increasing applied field, and decreasing barrier thickness or height, because of increased carrier sweepout rates.
Abstract: We have measured the heavy hole excitation saturation intensity in GaAs/AlGaAs quantum wells as a function of applied electric field and AlGaAs barrier design. We find that the saturation intensity increased with increasing applied field, and decreasing barrier thickness or height, because of increased carrier sweep‐out rates. Time‐resolved sweep‐out time and temperature‐dependent saturation intensity measurement point out the roles of both thermionic emission and tunneling in the field and barrier‐dependent carrier escape time. By reducing the barrier Al composition from 30 to 20%, we achieved an increase in the saturation intensity by a factor of ∼6.
58 citations
TL;DR: In this paper, the magnetic properties of peridotites from ODP Hole 670A have been studied and the degree of serpentinization was determined by a new method which combines saturation magnetization and whole-rock iron content.
58 citations
TL;DR: In this article, the saturation hyperfine-field of antiferromagnetic coherent γ-Fe precipitates in a Cu 100− x Al x matrix (0⩽ x ⩽14) was found to increase remarkably with increasing x, i.e., rising lattice expansion of the matrix.
Abstract: Experimental results from 57 Fe Mossbauer-effect investigations on epitaxial, γ-Fe ultrathin films and on γ-Fe precipitates are presented. Depending on the preparation conditions, low-moment anti-ferromagnetic Fe or high-moment ferromagnetic Fe is observed in fcc-Fe (0 0 1) films on Cu (0 0 1), and high-moment Fe in fcc-Fe (0 0 1) films on Cu 3 Au (0 0 1). Isomer-shift values suggest that this behavior is related to different lattice strains. The saturation hyperfine-field of antiferromagnetic coherent γ-Fe precipitates in a Cu 100− x Al x matrix (0⩽ x ⩽14) was found to increase remarkably with increasing x , i.e., rising lattice expansion of the matrix. For γ-Fe precipitates in Cu, the magnetic transition temperature and the saturation hyperfine-field show an anomalous increase above a critical particle size indicating a suggested structural phase transition. Very small precipitates show superparamagnetism.
TL;DR: In this paper, four polycomponent systems based on LaCo13 have been studied: La(Co1−xFex)13, La (Co 1−xAlx) 13, La(Al 0.4Fe 0.3)13 and La 0.7Nd0.3
Abstract: Four polycomponent systems based on LaCo13 have been studied: La(Co1−xFex)13, La(Co1−xAlx)13, La(Co1−x−yFexAly)13, and La0.7Nd0.3(Co0.7Fe0.3)13. These 1:13 systems were studied because of their potential for permanent magnet fabrication. LaCo13 has a high 3d metal content, the highest for any known rare‐earth intermetallic, a 13 kG saturation induction, and a high Tc (1318 K). Unfortunately, it is cubic and lacks anisotropy. The substituted systems were examined as a portion of a program to find LaCo13‐based systems of applications significance. Replacement of Co in LaCo13 by Fe and/or Al leads to a rapid decline in Tc for all systems studied. Replacement of Co by Al results in a decline in moment, whereas replacement by Fe leads to a rise in moment to 2.39μB/3d atom for La(Co0.4Fe0.6)13, as compared to 2.46μB/3d atom for Fe0.7Co0.3. Analysis of the magnetic data shows that vacancies occur in both half‐bands for LaCo13 (4.8 spin up and 3.24 spin down) but in only one half‐band in La(Co1−xAlx)13 for x≥0.2....
TL;DR: The magnetic ordering of R2BaNiO5 (R Y, Er) has been studied by neutron powder diffraction as mentioned in this paper, and the results show that the Ni-Er interactions are predominant between 33 and 16 K, and, at lower temperatures, cooperative Er-Er interaction leads to a saturation of the Er3+ ordered moments at T = 4 K.
TL;DR: In this article, the saturation behavior of InGaAsP optical amplifiers for input pulsewidths of 15 ps and 150 fs was studied and the measured output saturation energies were 150 and 40 fJ, respectively.
Abstract: The saturation behavior of InGaAsP optical amplifiers is studied for input pulsewidths of 15 ps and 150 fs. The measured output saturation energies are 150 and 40 fJ, respectively. A simple rate equation model based on pump-probe results predicts the observed pulsewidth-dependent saturation behavior. >
TL;DR: In this paper, the crystal structure of Bi2CuO4 has been investigated and its magnetic structure solved by neutron powder diffraction, which is perfectly described in the space group P4/ncc.
Abstract: The crystal structure of Bi2CuO4 has been reinvestigated and its magnetic structure solved by neutron powder diffraction. The crystal structure, according to earlier work, is perfectly described in the space group P4/ncc. Contrary to the dimeric magnetic behaviour suggested in a recent paper, the title compound becomes long-range antiferromagnetically ordered below 50 K. The ground state has Cz symmetry and the crystallographic magnetic group is P4/n'c'c'. The magnetic moment of copper atoms at 1.5 K is 0.93(6) mu B, which is very close to the saturation moment of spin-only Cu(II)(d9).
Patent•
23 Jul 1990
TL;DR: Magnetic record media are described that have an overlying or underlying magnetically saturable high permeability keeper layer in addition to a high coervicity magnetic layer in which magnetic signals are stored as mentioned in this paper.
Abstract: Magnetic record media are described that have an overlying or underlying magnetically saturable high permeability keeper layer in addition to a high coervicity magnetic layer in which magnetic signals are stored. These media are used in magnetic signal processing devices whose transducers are capable of generating a keeper layer-saturating bias flux. In signal reproduction the bias flux magnetically forms a saturation zone in the nature of virtual gap in the keeper layer that directs signal flux between the media and the transducer.
TL;DR: The stability of the magnetic parameters of several commercially available media was studied by measuring the bulk magnetic properties before and after exposure to different accelerated corrosion tests in environments of elevated temperature and humidity, and also in environments with traces of reactive species as discussed by the authors.
Abstract: The stability of the magnetic parameters of several commercially available media was studied by measuring the bulk magnetic properties before and after exposure to different accelerated corrosion tests in environments of elevated temperature and humidity, and also in environments with traces of reactive species of Cl/sub 2/, H/sub 2/S, and NO/sub 2/. Large corrosion effects were found reflected in irreversible reduction in the saturation and remanent magnetization of the metal particle and some of the thin-film media. Considerable loss of magnetization was also observed in the CrO/sub 2/ media under high-humidity conditions. The Co-modified iron oxide media experienced a considerable reduction in their coercivity. Only the gamma-iron oxide and the Ba-ferrite particulate media and a CoCrTa thin-film alloy with a high content of Cr were essentially stable. >
TL;DR: In this paper, the authors show that at low temperatures the magnetization curve of a dilute magnetic semiconductor exhibits an apparent saturation which is followed by magnetization steps (MSTs), which are caused by crossings of energy levels for pairs of nearest neighbor (NN) magnetic ions.
Abstract: At low temperatures the magnetization curve of a dilute magnetic semiconductor (DMS) exhibits an apparent saturation which is followed, at higher fields, by magnetization steps (MSTs). These MSTs are caused by crossings of energy levels for pairs of nearest‐neighbor (NN) magnetic ions. The fields where the MSTs occur yield the NN exchange constant JNN. Examples of data obtained in both dc and pulsed magnetic fields are presented, and values of JNN for several II‐VI DMSs containing Mn++ are given. The apparent (or technical) saturation value Ms, and the magnitude δM of each MST, indicate that the Mn++ ions are randomly distributed over the cation sites. A dramatic narrowing of the MSTs, and a fine structure, are observed in pulsed‐field experiments on some DMSs. The fine structure in Cd1−xMnxS is attributed to two types of NNs (with different JNN) in the wurtzite structure of this material. The theory of the MSTs, including the effects of distant neighbors and of the Dzyaloshinski–Moriya interaction, is re...
TL;DR: In this paper, the authors measured the isothermal remanent magnetization M rem of an YBa 2 Cu 3 O 7 crystal and used the extended bean model to fit the M rem (H ) data.
Abstract: The isothermal remanent magnetization M rem of an YBa 2 Cu 3 O 7 crystal was measured as function of the maximum applied field 10 Oe⩽ H m ⩽40 kOe, for several isotherms 42K⩽ T ⩽65K, for H m ⊥ c and H m ∥ c Above an onset field for flux penetration H p , M rem initially increases sharply with H m and then crosses over to a saturation value An extended Bean model is used to fit the M rem ( H ) data The derived onset field for T >50K is approximately linear with T and is in agreement with the lower critical fields H c1 ( T ) measured by other techniques At lower temperatures, however, H p continues to increase We incorporate surface barriers in the extended Bean model and consider the possibility that the low-temperature increase in H p might be due to such barriers
TL;DR: In this paper, the surface magneto-optical Kerr effect is used to measure magnetic hysteresis loops for Ni bilayers previously studied by ferromagnetic resonance, and the approach to saturation in the [11] direction confirms the existence of enhanced fourfold inplane magnetic anisotropy, attributed to the effect of arrays of misfit dislocations arising during the epitaxial growth of bcc Ni overlayers on ultrathin layers of Bcc (001)Fe.
Abstract: Surface magneto‐optical Kerr effect is used to measure magnetic hysteresis loops for Ni‐Fe bilayers previously studied by ferromagnetic resonance [Phys. Rev. 38, 12879 (1988)]. The approach to saturation in the [11] direction confirms the existence of enhanced fourfold in‐plane magnetic anisotropy, attributed to the effect of arrays of misfit dislocations arising during the epitaxial growth of bcc Ni overlayers on ultrathin layers of bcc (001)Fe. The [11] magnetization curves for 10 monolayers (ML) of Ni on 7 ML of Fe shows a breaking of symmetry between positive and negative fields. This is ascribed to spin configurations frozen during growth.
TL;DR: In this article, the effect of irradiation at two different frequencies on a spin system was studied in the context of continuous wave electron paramagnetic resonance (EPR) spectroscopy, where ω2 and ω1 are the frequencies of two incident microwave levels.
Abstract: The equation of Anderson [Phys. Rev. 102, 151 (1956)] (ω2−ω1)2=(γH0−ω1)2+γ2H21, which describes resonance conditions if relaxation times are long and irradiation at two frequencies is applied to a spin system, has been studied experimentally in the context of continuous wave electron paramagnetic resonance (EPR) spectroscopy. Here ω2 and ω1 are the frequencies of two incident microwave levels, one of which is much stronger than the other and is of amplitude H1. γH0 is the resonant condition if just one frequency is applied. Magnetization at either ω1 or ω2 has been observed as a function of sweep of the static magnetic field, sweep of ω2 and also sweep of the amplitude H1. Observation of magnetization at frequency ω1 corresponding to the strong microwave field H1 replicates the rotary saturation experiment of Redfield [Phys. Rev. 98, 1787 (1955)]. Multi‐quantum effects are studied with the two frequencies well separated and also when they lie within the width of a single homogeneous line. In addition, dat...
TL;DR: A numerical study of the two-dimensional classical XY model with weak random anisotropy at zero temperature with an important aftereffect is observed, which should give smaller remanence after much longer computer time.
Abstract: We present a numerical study of the two-dimensional classical XY model with weak random anisotropy at zero temperature. Zero-field configurations obtained by ultrafast cooling, first-magnetization curves, and hysteresis loops have been calculated for different random-anisotropy-to-exchange ratios. In zero field, a pinning of vortices by the random-anisotropy field occurs. It prevents the binding then collapsing of pairs of opposite charges and thus leads to a nonferromagnetic ground state. Applying a magnetic field causes a progressive depinning of vortices that disappear in pairs until saturation. Starting from saturation and decreasing the applied field leads, in zero-field, to a magnetic state of large remanent magnetization. However, an important aftereffect is observed. It should give smaller remanence after much longer computer time. Then, the reversal of magnetization in negative fields occurs through a peculiar process that involves the formation and collapse of new kinds of topological defects (infinite strings). These linear defects are in fact the ultimate stage in the shrinking of domains oriented in the initial direction of saturation. Their collapse occurs abruptly through the creation and propagation in opposite directions, along the defect, of an unbound vortex-antivortex pair.
TL;DR: In this paper, it was shown by magnetic measurements that the inclusions are ferromagnetic single-domain particles embedded in a paramagnetic matrix, which behave like superparamagnets at sufficiently high temperatures.
Abstract: According to small-angle X-ray scattering, amorphous Ni-P contains some volume per cent of metal-rich precipitations. During annealing, their diameters grow from about 2 nm in the as-prepared state to about 6 nm. It is shown by magnetic measurements that the inclusions are ferromagnetic single-domain particles embedded in a paramagnetic matrix. At sufficiently high temperatures such systems behave like superparamagnets. At 4.2 K, thermal agitation is too weak to flip the elementary magnetic moments. In this case, magnetisation curves can allow the authors to determine the coercivities and average saturation magnetisations. Annealing induces the two quantities measured at 4.2 K to change proportional to each other. This experimental fact justifies the application of a theory developed for fine non-interacting ferromagnetic particles having a magnetic shape anisotropy. The increase in the spontaneous magnetisation is attributed to the decomposition of the inclusions. With the aid of an approximation procedure the starting value of the phosphorus content and its decrease during annealing are estimated. These results and the values derived for the shape anisotropy agree well with those obtained through small-angle X-ray scattering. The starting phosphorus concentration of the precipitations proved to be independent of their volume fraction and the average composition of the samples. The observed kinetics fit in with the assumption of an activation energy spectrum. The lower limit starts at about 1.4 eV and is shifted on annealing to higher values.
Patent•
21 May 1990TL;DR: In this article, a thin film magnetic head has a first magnetic core member carried by a substrate, a gap layer formed on the first core member, and a second core member formed in a spaced relation with the core member.
Abstract: A thin film magnetic head has a first magnetic core member carried by a substrate, a gap layer formed on the first magnetic core member, and a second magnetic core member formed in a spaced relation with the first magnetic core member. The second magnetic core member is coupled to the first magnetic core member to form a magnetic path and to have an end portion of the gap layer sandwiched by gap defining portions of the first and second magnetic core members. A coil conductor is wound about the magnetic path. In one embodiment, the first magnetic core member includes a first magnetic layer made of a magnetic material having stable magnetic properties during heat treatment and the second magnetic core member includes a second magnetic layer made of a material having a saturation flux density higher than that of the material of the first magnetic core member.
17 Apr 1990
TL;DR: The magnetic properties and the microstructure of Fe-Ta-N-O film prepared by the facing targets sputtering method are reported in this article, where the addition of a small amount of Ta to Fe-NO is shown to improve the thermal stability of the magnetic properties at 600 degrees C without a decrease in saturation flux density (B/sub s/=19 kG).
Abstract: The magnetic properties and the microstructure of Fe-Ta-N-O film prepared by the facing targets sputtering method are reported. The addition of a small amount of Ta to Fe-N-O shown to improve the thermal stability of the magnetic properties at 600 degrees C without a decrease in saturation flux density (B/sub s/=19 kG). The microcrystallized state of Fe-Ta-N-O film observed by X-ray diffractometry is related to the good soft magnetic properties. >
TL;DR: In this paper, the relativistic multiresonator magnetron is analyzed in cylindrical geometry, using the two-dimensional particle-in-cell simulation code magic, and detailed comparisons are made between the simulation results and the experiments by A. Palevsky and G. Bekefi.
Abstract: The relativistic multiresonator magnetron is analyzed in cylindrical geometry, using the two‐dimensional particle‐in‐cell simulation code magic. Detailed comparisons are made between the simulation results and the experiments by A. Palevsky and G. Bekefi [Phys. Fluids 22, 986 (1979)] using the A6 magnetron configuration. Within a constant scale factor, the computer simulations show a similar dependence of microwave power on magnetic field, with dominant excitations in the π and 2π modes. In the preoscillation regime, the electron flow in the simulations differs substantially from the ideal Brillouin flow model. In the nonlinear regime, the saturation is dominated by the formation of spokes.
TL;DR: In this paper, the magnetic field is amplified due to the formation of flux sheets with saturation due either to resistive diffusion (kinematic regime) or to nonlinear effects (dynamic regime).
Abstract: Two‐dimensional (2‐D) magnetohydrodynamic turbulence is investigated for weak initial magnetic fields using numerical simulation. It is found that the magnetic field is amplified owing to the formation of flux sheets with saturation due either to resistive diffusion (kinematic regime) or to nonlinear effects (dynamic regime). In the kinematic regime, which corresponds to the problem of passive scalar convection by 2‐D Navier–Stokes turbulence, the saturation value of the magnetic energy is observed to scale as EMmax∝η−0.8 in approximate agreement with a simple theoretical estimate, EMmax/EM(0)≂Rm, where Rm is the magnetic Reynolds number. Because of the strongly disparate kinetic and magnetic energy spectra in the kinematic regime, roughly EVk∼k−3, EMk∼k, dynamic interaction on small scales already occurs at very small global energy ratios EM/EV, giving rise to strongly enhanced kinetic energy dissipation. In the fully dynamic regime (reached for EM/EV‖t=0>R−1m) global magnetic and kinetic energies become...
TL;DR: A micromagnetic study of the effects of cobalt modification on the magnetization reversal of elongated γ-Fe2O3 particles is presented in this paper, where the undoped particle core is identified as the site for the initial irreversible processes.
Abstract: A micromagnetic study of the effects of cobalt modification on the magnetization reversal of elongated γ‐Fe2O3 particles is presented. Equilibrium states and irreversible switching are computed numerically. The undoped particle core is identified as the site for the initial irreversible processes. For certain material parameters this can lead to a core‐reversed state. The enhancement and the saturation of the enhancement of the switching field are explained as a function of doping level. Extrapolation of the numerical results suggests that approximately one monolayer of cobalt‐ferrite is sufficient to yield significant enhancement of the coercivity.
TL;DR: In this article, the dependence of the magnetic transition temperature and the magnetic hyperfine field on particle volume and on matrix lattice parameter in coherent antiferromagnetic γ-Fe precipitates in Cu100−xAlx matrices was determined by 57Fe Mossabuer spectroscopy and dc susceptibility measurements.
Abstract: We have determined the dependence of the magnetic transition temperature TN and of the magnetic hyperfine field Bhf on particle volume and on matrix lattice parameter in coherent antiferromagnetic γ-Fe precipitates in Cu100−xAlx matrices (0⩽x⩽14) by 57Fe Mossabuer spectroscopy and dc susceptibility measurements. The average particle diameter d was determined precisely by transmission electron microscopy (TEM). The behavior of TN(d) and of Bhf(d) at 4.2 K for γ-Fe in Cu is in agreement with a suggested structural phase transition at TN for d⪆20 nm. Precipitates smaller than d≈15–20 nm show superparamagnetism. The saturation hyperfine-field (and consequently the atomic Fe moment) of γ-Fe was found to increase remarkably with increasing lattice expansion of the Cu Al matrix.
TL;DR: In this paper, a detailed study of the different magnetization components in a fine particle system is presented, and the effects of particle interactions on the magnetic behavior of the system are also discussed.
Abstract: A detailed study of the different magnetization components in a fine particle system is presented. From measurements of these components, it is shown that the various components are related. The effects of particle interactions on the magnetic behavior of the system are also discussed. This behavior is shown to be analogous to that of spin-glass alloys. Low-field measurement are greatly affected by particle interactions, whereas interactions have little effect on saturation measurements. >