Showing papers on "Single domain published in 1997"
TL;DR: In this article, the first magnetization measurements of individual ferromagnetic nanoparticles (15-30 nm) at very low temperatures (0.1-6 K) were presented.
Abstract: Presented are the first magnetization measurements of individual ferromagnetic nanoparticles (15--30 nm) at very low temperatures (0.1--6 K). The angular dependence of the hysteresis loop evidenced the single domain character of the particles. Waiting time, switching field, and telegraph noise measurements showed for the first time that the magnetization reversal of a well prepared ferromagnetic nanoparticle can be described by thermal activation over a single-energy barrier as originally proposed by N\'eel and Brown. The ``activation volume'' estimated by these measurements was close to the particle volume.
525 citations
TL;DR: In this paper, the magnetic switching of a continuous Permalloy film is artificially modified by lithographically structuring an antidot array, which introduces a spatially variant shape anisotropy field that competes with the intrinsic uniaxial anisotropic of the continuous film.
Abstract: The magnetic switching of a continuous Permalloy film is artificially modified by lithographically structuring an antidot array. The antidots introduce a spatially variant shape anisotropy field that competes with the intrinsic uniaxial anisotropy of the continuous film. This results in a well-defined periodic domain structure at remanence as observed by scanning Kerr microscopy, and which could be significant for high-density data storage. A micromagnetic calculation explains the structure and indicates optimum anisotropy conditions for data storage applications.
153 citations
TL;DR: In this paper, the numerical integration of the Gilbert equation of motion resolves magnetisation processes in time and in space, and the calculated domain patterns are in qualitative agreement with magnetic images obtained from Lorentz electron microscopy.
109 citations
TL;DR: In this article, a new model for the magnetic susceptibility of singledomain (SD) grains measured at different frequencies was proposed, which is divergent from the now well-established theory of SD behaviour.
Abstract: SUMMARY A recent paper (Dearing et al. 1996) on the use of frequency dependence of magnetic susceptibility (xfd) in magnetic grain-size investigations of environmental materials has proposed a fundamentally new model for the magnetic susceptibility of singledomain (SD) grains measured at different frequencies, and is divergent from the now well-established theory of SD behaviour. This new model appears to be founded on a confusion about the behaviour of SD grains, as predicted by theory, and magnetic measurements of real materials, which naturally have a distribution of magnetic grain sizes. Here I try to clear up this confusion by showing how different log-normal distributions of magnetic grain sizes affect the frequency dependence of magnetic susceptibility measurement. This analysis highlights that the limiting maximum xfd value of -15 per cent obtained for environmental materials can be explained simply as a constraint imposed by the magnetic grain-size distribution having a finite minimum width (-1.0 on a natural log scale). There is no reason to suppose that if the grain-size dispersion was narrower higher Xfd values could not be observed. Furthermore, the xfd value is non-unique and so cannot be used quantitatively to determine the amount or grain-size distribution of SD grains in a sample
103 citations
TL;DR: In this article, the magnetization reversal process in arrays of sub-micron Ni and Co wires was investigated by means of magnetization and torque experiments together with micromagnetic calculations.
Abstract: We have investigated the magnetization reversal processes in arrays of sub-micron Ni and Co wires by means of magnetization and torque experiments together with micromagnetic calculations. The wires were produced by electrodeposition in the cylindrical pores of track-etched polymer membranes. Diameters in the range 35–400 nm have been studied. The arrays of Co and Ni nanowires display different magnetic behaviors. Particular emphasis is given to the competing shape and crystal magnetic anisotropies that exist in the Co nanowire system. In both systems, explaining the experimental results requires domain formation, except for the smallest diameters where single domain behavior occurs.
86 citations
TL;DR: Magnetic domain behavior was imaged in calcium-doped lanthanum manganese trioxide films as mentioned in this paper, showing that magnetic domains behave differently at temperatures that are well below and near the Curie temperature T c.
Abstract: Magnetic domain behavior was imaged in calcium-doped lanthanum manganese trioxide films. Magnetic domains behave differently at temperatures that are well below and near the Curie temperature T c. At low temperatures the domains are very stable. As temperature rises toward T c, domain-domain interactions become weaker and domains become highly mobile and subject to merging and splitting, yet the domains are still traceable. The contrast (which is a measure of magnetization) and size of domains continuously reduce to zero. The temperature at which the domains disappear agrees with the T c obtained by a macroscopic magnetization measurement. Sample defects such as scratches tend to attract magnetic domains.
79 citations
TL;DR: In this article, the magnetic properties of Fe 38.5Pt, Fe 39.5pt and Fe 50.0pt alloys were investigated using a vibrating sample magnetometer, and correlated with the microstructures of the alloys by transmission electron microscopy.
73 citations
TL;DR: In this article, the first triple-axis neutron scattering measurements of magnetic fluctuations in nanoparticles using an antiferromagnetic reflection were presented, and the results were consistently analyzed on the basis of a simple model with uniaxial anisotropy and the N\'eel-Brown theory for the relaxation.
Abstract: We present the first triple-axis neutron scattering measurements of magnetic fluctuations in nanoparticles using an antiferromagnetic reflection. Both the superparamagnetic relaxation and precession modes in $\ensuremath{\sim}15\mathrm{nm}$ hematite particles are observed. The results have been consistently analyzed on the basis of a simple model with uniaxial anisotropy and the N\'eel-Brown theory for the relaxation.
73 citations
TL;DR: In this paper, the magnetoresistive behavior of epitaxial thin films of the conductive ferromagnetic oxide SrRuO3 with different domain structures grown on both miscut (001) SrTiO3 and exact (1) LaAlO3 substrates was studied.
Abstract: We have studied the magnetoresistive behavior of epitaxial thin films of the conductive ferromagnetic oxide SrRuO3 with different domain structures grown on both miscut (001) SrTiO3 and exact (001) LaAlO3 substrates. A strong anisotropic magnetoresistance (MR) has been observed in the single domain SrRuO3 thin film on miscut (001) SrTiO3 substrate. In contrast, the SrRuO3 thin film on (001) LaAlO3 substrate shows identical MR behavior in two orthogonal directions on the film due to the presence of 90° domains in the plane. For both the films, large negative magnetoresistance effects (∼10%) were observed when the current and the applied magnetic field are parallel. This is attributed to a reduction in spin fluctuations near Tc and to magnetization rotation leading to a change in the angle between the current and magnetization at low temperatures.
63 citations
TL;DR: In this article, the intensity of rotational remanent magnetization (RRM) acquired by single-domain greigite at a rotation frequency of 5 rps was combined with measurements of anhysteretic Remanent Magnetization (ARM) to calculate the effective biasing field (Bg) that produced the RRM.
Abstract: SUMMARY
The intensity of rotational remanent magnetization (RRM) acquired by single-domain greigite at a rotation frequency of 5 rps was combined with measurements of anhysteretic remanent magnetization (ARM) to calculate the effective biasing field (Bg) that produced the RRM. Samples of single-domain greigite had Bg values between -137 and -84 μT, and a MDFRRM of c. 80 mT. By contrast, a suite of natural and synthetic ferrimagnetic iron oxide samples, including single-domain magnetite and yFe3O4 tape particles, acquired Bg values between -3 and -14 μT, and MDFRRM ranged between 43 and 68 mT (when RRM was acquired). Multidomain magnetite did not acquire a RRM. Bg values at 5 rps were calculated from previously published data for magnetite particles of different grain sizes, which revealed a minimum Bg value of -24 μT and a MDFRRM of 57 mT for the finest fraction (0.2-0.8 μm in diameter). In a geological example, measurements of Bg and MDFRRM were used to detect the presence of greigite in a 4 m long Late Weichselian sediment core. Variations in inclination, declination and the intensity of the natural remanent magnetization (NRM) correlate with changes in magnetic mineralogy.
62 citations
TL;DR: In this article, single domain e-Fe3N nitride particles have been synthesized by chemical reduction followed by nitridation at 823 K. The reduction of intrinsic magnetizations and Curie temperatures with decreasing particle size is attributed to canted spin structure predominantly at the surface compared to the bulk of the particles.
Abstract: Single domain e-Fe3N nitride particles have been synthesized by chemical reduction followed by nitridation at 823 K. The e-Fe3N phase crystallizes in hexagonal structure with unit cell parameters, a=2.70 A and c=4.39 A. There is a reduction of unpaired d electrons for intraband polarization as the nitrogen contributes to the density of states and thus results in lowering of magnetic moments. The reduction of intrinsic magnetizations and Curie temperatures with decreasing particle size is attributed to canted spin structure predominantly at the surface compared to the bulk of the particles. Chemisorption of oxygen results in the formation of oxynitride layer at the surface with a ferromagnetic coupling to the spins in the core of the particle. Mossbauer study of e-Fe3N particles exhibits the coexistence of ferromagnetic and superparamagnetic particles and corroborates the observed magnetic properties.
TL;DR: The size and orientation dependent micromagnetic structures of epitaxial Fe(001) thin film elements with in-plane anisotropy were reported in this paper, where a transition from single domain to multidomain remanent states was observed upon reducing the element size.
Abstract: The size and orientation dependent micromagnetic structures of epitaxial Fe(001) thin film elements with in-plane anisotropy are reported. A transition from single domain to multidomain remanent states is observed upon reducing the element size beneath $\ensuremath{\sim}50\ensuremath{\mu}\mathrm{m}$, indicating that the in-plane dipolar field becomes competitive with the magnetocrystalline anisotropy at this size. Because of this competition, distinct micromagnetic structures arise according to the orientation of the element edges. The epitaxial elements are of high structural quality allowing the micromagnetic behavior to be controllably modified.
TL;DR: In this article, the magnetic properties of randomly oriented assembly of noninteracting single-domain particles with cubic anisotropy are studied in detail, and it is shown that the coercive force of such assemblies is almost independent of the value of the damping parameter.
TL;DR: In this paper, a pre-exponential frequency factor of ǫ 0 in the Neel-Arhennius relaxation equation was derived for magnetoferritin and the SPM threshold size at room temperature for Maghemite was estimated to be 20-27 nm.
Abstract: Magnetization and Mossbauer measurements on maghemite particles with an average particle diameter of 10 nm have been made in the temperature range from 5 K to 353 K spanning the superparamagnetic (SPM) and stable single domain (SD) regimes. The maghemite particles were produced within the iron-storage protein ferritin, resulting in a narrowly-sized, weakly interacting nanocomposite material called magnetoferritin. Experiments combining hysteresis measurements, low temperature remanence, and Mossbauer spectroscopy were used to characterize magnetoferritin and to provide experimental estimates of (1) the pre-exponential frequency factor ƒ0 in the Neel-Arhennius relaxation equation; (2) the SPM threshold size at room temperature for maghemite; and (3) the SD value of Hr/Hc at 0 K. The frequency factor was determined from the difference in blocking temperatures measured by dc magnetization and Mossbauer spectroscopy, yielding a value of f0≈109 Hz. This agrees well with the standard value and justifies the usually assumed superparamagnetic blocking condition of KV = 25 kT for remanence measurements. The SPM threshold size at room temperature for remanence measurements was estimated to be 20–27 nm and the extrapolated SD value at 0 K for Hr/Hc is 1.32. The latter value is slightly larger than the theoretical value of 1.09 but may be more appropriate for weakly interacting SD particles commonly found in sediments and soils. However, ƒ0 for ferrimagnetic magnetoferritin is a factor of 103 lower than was determined previously for native ferritin, which contains antiferromagnetic ferrihydrite cores. The difference in ƒ0 values between the two varieties of ferritin is probably related to the two different types of magnetic spin ordering of the core minerals and suggests that the higher value of ƒ0 is more appropriate for antiferromagnetic minerals like hematite and goethite, whereas the lower value is more appropriate for ferrimagnetic minerals like maghemite, magnetite, or greigite.
TL;DR: In this paper, the origin of coercivity in precipitation hardened Sm-Co magnets is investigated by considering domain-wall pinning at boundary phase and Z phase inhomogenities, and it is found that the hexagonal Z phase has no direct influence on the coercivity.
Abstract: The origin of coercivity in precipitation hardened Sm–Co magnets is investigated. By considering domain-wall pinning at boundary phase and Z phase inhomogenities, it is found that the hexagonal Z phase has no direct influence on the coercivity. The intuitive assumption of plane domain walls made in a recent calculation is unrealistic but has no direct effect on the coercivity. However, due to the comparatively large size of the 12:17 cells, the calculated three dimensional domain-wall curvature is sufficiently large to assure a nearly ideal nestling of the domain walls to the 1:5 cell boundary. This nestling yields a coercivity increase from about 0.1 to about 1 T and is therefore responsible for the high coercivity of 2:17 based Sm–Co magnets.
TL;DR: In this paper, the angular dependence of the switching field Hs for single-domain particles was measured using a magnetic force microscope with an in situ electromagnet, and quantified the extent to which the particles can be considered "single-domain".
Abstract: Quantitative measurements of the switching field properties of individual single-domain particles are both scientifically and technologically important. Such data are relevant for the engineering of a patterned magnetic storage medium where a single bit of information corresponds to individual single-domain particles with sizes consistent with storage densities >50 Gbit/in2. By electroplating into Al2O3 and track-etched polycarbonate filters, we have prepared particles over a large range of radii from R=20–500 nm, and have characterized them by transmission electron microscopy. Using a magnetic force microscope with an in situ electromagnet, we have quantified the extent to which the particles can be considered “single-domain.” We have also measured the angular dependence of the switching field Hs for these particles. At zero degrees, Hs lies above the curling curve for R/R0>4, and falls below the curling curve for R/R0<2, where R0 is the exchange length (R0=20.6 nm for Ni). At intermediate radii, the ang...
TL;DR: In this paper, the authors show that demagnetizing fields have a major role in determining the magnetic response of the arrays, which show high saturation fields and a coercivity which is lower than predicted by curling or uniform rotation models.
Abstract: Nanometer-sized Co arrays consisting of 200 nm or 20 nm diameter cylindrical islands, occupying a fractional surface area of 50 to 65%, have been synthesized by electrodeposition through the pores of suitable Al oxide templates. An increase in coercivity for 20 nm compared to 200 nm diameter Co island arrays is explained in terms of a transition to a single domain state. In this size range, demagnetizing fields have a major role in determining the magnetic response of the arrays, which show high saturation fields and a coercivity which is lower than predicted by curling or uniform rotation models. A high effective anisotropy is important in obtaining relatively high values of coercivity (up to 1700 Oe) in highly packed arrays.
TL;DR: In this article, the authors used magnetic force microscopy to study the magnetic domain and domain wall structures in pseudo-single-domain grains (5-20 gm) of magnetite (Fe304).
Abstract: Magnetic domain and domain wall structures in pseudo-single-domain grains (5-20 gm) of magnetite (Fe304) were studied using magnetic force microscopy. Many of the observed micromagnetic features can be explained by the magnetostatic effects of surfaces and grain edges and interactions within and between walls. Domain walls were frequently subdivided into 1-3 opposite polarity segments separated by Bloch lines, although some walls contained no Bloch lines. Subdivided walls display a characteristic zigzag structure along the easy axis direction, where zigzag angles can be as high as 200-40 o . The zigzagging structure, in addition to wall segmentation, further minimizes the magnetostatic energy of the walls. Bloch lines can be (de)nucleated during wall displacement or after repeated alternating field (AF) demagnetization. Within individual walls, the number of Bloch lines and their pinning locations were found to vary after repeated AF demagnetization demonstrating that walls, like individual grains, can exist in several different local energy minima. The number of Bloch lines appears to be independent of domain state, but frequently the polarity of the wall was coupled with the direction of magnetization in the adjoining domains, such that wall polarity alternates in sign between adjacent walls across an entire grain. Even after the domain magnetization is reversed, the same sense of wall chirality is maintained across the grain producing unique grain chiralities. For one particular grain it was possible to reconfigure a likely three-dimensional (3-D) domain structure. The body and surface structures result primarily from a combined volume magnetostatic interaction between all grain surfaces and magnetocrystalline anisotropy. Finally, commonly observed open-flux features within the interior of grains or along grain edges terminating planar domains are inconsistent with the prediction of edge closure domain formation based on recent 2- D micromagnetic models. Our observations suggest that 3-D micromagnetic models are required to model results even for grains larger than 1 gm.
IBM1
TL;DR: In this paper, the magnetic properties of nanoscale magnetic films with large perpendicular anisotropy were studied and the results for the field and temperature dependence of the domain wall velocity suggest that for thin films the hysteresis can be described as a depinning transition of domain walls rounded by thermal activation for finite temperatures.
Abstract: We study the magnetic properties of nanoscale magnetic films with large perpendicular anisotropy comparing polarization-microscopy measurements on ${\mathrm{Co}}_{28}{\mathrm{Pt}}_{72}$-alloy samples based on the magneto-optical Kerr effect with Monte Carlo simulations of a corresponding micromagnetic model. In our model the magnetic film is described in terms of single-domain magnetic grains interacting via exchange as well as via dipolar forces. Additionally, the model contains an energy barrier which has to be overcome in order to reverse a single cell and a coupling to an external magnetic field. Disorder is taken into account. We focus on the understanding of the dynamics especially the temperature and field dependence of the magnetization reversal process. The experimental and simulation results for hysteresis, the reversal mechanism, domain configurations during the reversal, and the time dependence of the magnetization are in very good qualitative agreement. The results for the field and temperature dependence of the domain wall velocity suggest that for thin films the hysteresis can be described as a depinning transition of the domain walls rounded by thermal activation for finite temperatures.
TL;DR: In this article, the domain structures of the NdFe10.5Mo1.5 and Nd Fe10.6Mo 1.5Nx were studied by using magnetic force microscopy and a domain structure transition from complex maze to simple stripe was found.
Abstract: We succeed in preparing anisotropic magnetic powders with high performance based on the NdFe10.5Mo1.5Nx nitrides. The properties of these materials are favorable for permanent magnet application. The domain structures of the NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx were studied by using magnetic force microscopy. Upon nitrogenation, a domain structure transition from complex maze to simple stripe was found. This transition is due to the strongly uniaxial magnetocrystalline anisotropy induced by interstitial nitrogen atoms. Together with magnetic measurements, we have calculated the domain wall energy γ, exchange constant A, domain wall thickness δ, and critical single-domain particle size Dc of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx.
01 Apr 1997
TL;DR: In this article, the effect of permanent magnet magnetization patterns on shear force production was investigated for magnetic clutches and dual-facing magnet structures and magnet-and-steel structures with and without current.
Abstract: The problem of magnetic clutches is addressed by this paper. Specifically, the effect of permanent magnet magnetization patterns on shear force production is investigated. Dual-facing magnet structures and magnet-and-steel structures (with and without current) are evaluated by finite element techniques. Shear force production is shown to be strongly affected by magnetization patterns as well as geometric sizing.
TL;DR: In this article, the magnetic coupling in the two-phase nanostructure of Fe73.5Si15.5B7Nb3Cu1 has been investigated by SANS technique.
Abstract: The magnetic coupling in the two-phase nanostructure of Fe73.5Si15.5B7Nb3Cu1 has been investigated by SANS technique. The scattering function for partially aligned magnetic moments of ferromagnetic single domain particles following the Langevin statistics of superparamagnetism has been derived which describes the field and temperature dependency of the SANS profiles. Above the Curie temperature of the amorphous phase T
the nanocrystals show superparamagnetic scattering behaviour whereas below T
they interact by magnetostatic forces only and not by exchange coupling via the amorphous matrix.
TL;DR: The infinite hierarchy of differential-recurrence relations for the equilibrium transverse correlation functions appropriate to magnetic relaxation of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a uniform external magnetic fieldH0 is derived by averaging Gilbert's equation as discussed by the authors.
Abstract: The infinite hierarchy of differential-recurrence relations for the equilibrium transverse correlation functions appropriate to magnetic relaxation of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a uniform external magnetic fieldH0 is derived by averaging Gilbert’s equation. Exact expressions in terms of matrix continued fractions for the transverse complex magnetic susceptibility are obtained with the aid of linear-response theory by solving the infinite hierarchy. The principal features of the spectra are emphasized in figures showing the real and imaginary parts of the complex magnetic susceptibility. The accuracy and the range of the applicability of analytical results based on the effective eigenvalue method is established. It is shown that this method provides in general a good approximation to the exact solution with the exception of the range of low-to-intermediate barrier heights of the anisotropy potential where at small H0 there exists essentially a spread of the precession frequencies of the magnetization. @S0163-1829~97!03229-3#
TL;DR: In this paper, the lattice constant of the LaAlO3 lattice was determined using high resolution ω-ω2θ reciprocal space mapping over the 002 peak, however, it was not possible to determine the small splitting of the 2 peak due to the different twin domains.
TL;DR: In this paper, the authors developed an interpretation of magnetization data appropriate to materials where magnetization reversal occurs as a two-stage process: domain nucleation followed by domain wall motion, and applied it to films with perpendicular magnetic anisotropy.
Abstract: In this paper we develop an interpretation of magnetization data appropriate to materials where magnetization reversal occurs as a two-stage process: domain nucleation followed by domain wall motion, and apply it to films with perpendicular magnetic anisotropy. An interpretation of remanence curve data and time dependence data for a two-stage reversal system is proposed. The two principal remanence curves (IRM and DCD) yield data on the energy barrier distribution, while the delta-I plot which compares these two remanence curves offers a method of characterizing the relative importance of domain nucleation and domain wall motion. The interpretation is then applied to a series of magneto-optic thin films where the film thickness varies from 164 to 830 A. All but the thickest film show magnetization reversal is controlled by both domain nucleation and domain wall motion. In the 830 A film only domain wall motion appears important in controlling reversal.
TL;DR: In this paper, magnetic anisotropy constants and domain structures in arrays of magnetic dots 0.5 μm wide fabricated out of an epitaxial (0001) hcp cobalt film were measured.
Abstract: We have measured magnetic anisotropy constants and domain structures in arrays of magnetic dots 0.5 μm wide fabricated out of an epitaxial (0001) hcp cobalt film. Occurrence of a concentric stripe domain pattern for which the magnetization is mostly in-plane with small alternately up and down perpendicular components is found for a 25-nm-thick cobalt dot array. Interestingly, this sample produces a spin reorientation from a quasi in-plane to a fully perpendicularly oriented magnetization when the temperature is lowered, due to an increase of the perpendicular anisotropy at low temperature.
TL;DR: In this paper, Maghemite with spontaneous saturation magnetization M s = 320 kA m −1 at 200 K and a normalized high-field susceptibility χ /M o = 5.1 × 10 −6 m kA −1, practically independent of temperature.
01 Apr 1997
TL;DR: In this paper, the Gilbert equation of motion for magnetic nano-elements of arbitrary shape using a hybrid finite element/boundary element method was solved, and small scale domains in the remanent state were shown.
Abstract: The Gilbert equation of motion is solved for magnetic nano-elements of arbitrary shape using a hybrid finite element/boundary element method. NiFe elements show small scale domains in the remanent state, if a uniaxial anisotropy parallel to the short axis is assumed. In bars with one pointed end, the formation of the domains starts from the flat ends. Narrow elements with a width smaller than 0.2 /spl mu/m remain in a nearly single domain state.
TL;DR: In this paper, it is shown that the domain contrast in such extreme conditions cannot be explained with the usual theory of MFM image formation, in which the stray field from one body (tip or sample) is sensed by the other, without altering of the magnetization distributions.
Abstract: Domains were imaged by magnetic force microscopy (MFM) on materials where the domain size exceeds the sample thickness by three orders of magnitude. Selected samples are a magnetooptical medium and ultrathin cobalt films, all with perpendicular magnetization. A strong domain contrast is observed in both cases. This fact is confronted to the usual theory of MFM image formation, in which the stray field from one body (tip or sample) is sensed by the other, without altering of the magnetization distributions. It is shown that the domain contrast in such extreme conditions cannot be explained with that theory. On the contrary, Abraham and McDonald’s model, which considers the response of the sample to the tip field, is quantitatively compared to experiment. It is shown to provide a good qualitative description of the results, but not a quantitative one, because of oversimplification.
TL;DR: In this article, the magnetic properties of amorphous rare-earth 3D transition metal alloys are reviewed using current theoretical models to account for the experimental data available, and the dependence of the exchange integrals on the interatomic separation is determined.
Abstract: Work on the magnetic properties of amorphous rare-earth–3d-transition-metal alloys is reviewed using current theoretical models to account for the experimental data available. The exchange interaction and random magnetic anisotropy are shown to dominate the magnetization and magnetization reversal processes. Some new phenomena related to the effect of induced magnetic anisotropy on magnetization processes are considered. The results on the magnetoelastic properties of rare-earth alloys are systematized. The dependence of the exchange integrals on the interatomic separation is determined. It is shown that pressure significantly affects the magnetic structure and phase transitions in these magnetic materials.