Showing papers on "Magnetic structure published in 1975"
137 citations
TL;DR: In this paper, the atom positions in antiferromagnetic and ferroelectric BiFeO3 have been obtained by profile analysis of powder neutron diffraction data collected ant 42K and 293K.
Abstract: The atom positions in antiferromagnetic and ferroelectric BiFeO3 have been obtained by profile analysis of powder neutron diffraction data collected ant 42K and 293K The sublattice magnetization also determined at 42K, has been used to obtain a covalency parameter sum, Asigma 2+2Api 2+As2=134+or-05% An experiment to obtain further information about the neutron magnetic form factor, by complete separation of the nuclear and magnetic contributions using polarization analysis, is described
95 citations
TL;DR: In this article, the para-to-ferromagnetic transition in Fe2P has been studied using Mossbauer spectroscopy and the magnetic hyperfine fields drop abruptly from about half of their saturation values to zero at 214.5 K indicating a first order transition.
81 citations
TL;DR: Magnetic susceptibility, X-ray diffraction and neutron diffraction measurements have been made on quenched and slow-cooled samples of Ni2MnAl alloy as discussed by the authors, and the positions and intensities of the magnetic reflections are consistent with an antiferromagnetic cone spiral structure associated with the Mn atoms.
Abstract: Magnetic susceptibility, X-ray diffraction and neutron diffraction measurements have been made on quenched and slow-cooled samples of Ni2MnAl alloy. Above 300K the susceptibility is Curie-Weiss but on cooling below this temperature the susceptibility becomes field dependent. Neutron diffraction patterns indicate that the compound is chemically ordered into the B2 structure with some additional L21 (Heusler alloy) type of order, that is enhanced by slow cooling. At 4.2K magnetic scattering was observed in fundamental reflections and in pairs of satellite reflections which were displaced by +or-0.111a* from the reciprocal lattice points corresponding to the nuclear reflections. The positions and intensities of the magnetic reflections are consistent with an antiferromagnetic cone spiral structure associated with the Mn atoms. The collinear components are coupled ferromagnetically in (111) sheets with antiferromagnetic coupling between adjacent planes.
76 citations
TL;DR: In this paper, a modified anti-ferromagnetic spin structure is proposed, where the ferromagnetic ordering of the iron moments in the basal planes is partly destroyed and the magnetic unit cell is four times as large as the chemical unit cell, being doubled both along the a and the c axis.
Abstract: From the analysis of 57Fe and 119Sn Mossbauer spectra a modified anti-ferromagnetic spin structure is proposed. The ferromagnetic ordering of the iron moments in the basal planes is partly destroyed and the magnetic unit cell is four times as large as the chemical unit cell, being doubled both along the a and the c axis. The temperature variation of the reduced magnetic hyperfine field for Sn(1) strongly deviates from the corresponding quantity found for iron. The Neel temperature is found to be 368 K and the critical exponent β obtained is 0.340.
60 citations
TL;DR: The magnetic properties of the R Au 2 Si 2 compounds with R = Ce-Er have been investigated in this article, and it was found that the compounds for which R = Eu, Sm, Gd, Tb and Dy are antiferromagnetically ordered at temperatures ranging from 5.7 to 15.9°K.
54 citations
TL;DR: The magnetic structure of Mn 3 Si (bcc Fe 3 Al type crystal structure) at low temperatures has been determined by neutron diffraction using single crystal samples as mentioned in this paper, which is near the boundary of the Brillouin zone.
Abstract: The magnetic structure of Mn 3 Si (bcc Fe 3 Al type crystal structure) at low temperatures has been determined by neutron diffraction using single crystal samples. It is found that Mn 3 Si has a helical spin structure (Neel temperature 25.8 K) with a wave vector q parallel to one of directions and of magnitude 0.85·1/2·2π K 111 , which is near the boundary of the Brillouin zone. The magnetic structure is either a proper screw or a transversal sinusoidal structure and the magnetic moments at the two Mn sites are µ Mn I =1.72 µ B and µ Mn II =0.19 µ B . The temperature dependence of the magnitude of the wave vector q is similar to that of Cr. From these data the possibility of an itinerant electron antiferromagnetism of Mn 3 Si is suggested in comparison with the SDW in Cr.
39 citations
TL;DR: In this article, the magnetic properties of GdMg and TbMg were investigated by neutron diffraction and the spontaneous magnetization reached 4.5μB at 4.2 K and decreases as T2.
34 citations
TL;DR: In this article, the magnetic properties of CsCl−type intermetallics in terms of the RKKY model were investigated and the results for PrZn and NdMg are remarkable and form a discrepancy with the ferromagnetic nature of the heavy rare−earth counterparts of these compounds.
Abstract: Neutron−diffraction studies were performed on the compounds PrZn, NdZn, NdMg, and NdAg. The lattice constants were determined at 300 and 4.2 K. For all compounds the CsCl structure was confirmed at room temperature. The compound PrZn was found to be subject to a tetragonal distortion at 4.2 K. A very small tetragonal distortion exists probably also in NdZn and NdMg at 4.2 K. the magnetic moment of the rare−earth component and the magnetic structure type was determined. All compounds are antiferromagnetic at 4.2 K, PrZn and NdMg with the 〈0,0,π〉 structure, NdAg with the 〈π,π,0〉 structure. In view of the generally accepted explanation of the magnetic properties of CsCl−type intermetallics in terms of the RKKY model these findings for PrZn and NdMg are remarkable and form a discrepancy with the ferromagnetic nature of the heavy rare−earth counterparts of these compounds.
33 citations
TL;DR: In this paper, it was shown that NiS 2 has a non-collinear spin structure and the Ni spins with ordering of the first kind for fcc lattice make a constant angle θ with the principal axis of the electric field gradient at the Ni sites.
Abstract: Mossbauer experiment has been performed of 57 Fe doped in antiferromagnetic NiS 2 . The supertransferred hyperfine field of 19 kOe has been observed at 4.2 K. From the analysis of the supertransferred hyperfine field, it is concluded that NiS 2 has a non-collinear spin structure. The Ni spins with ordering of the first kind for fcc lattice make a constant angle θ with the principal axis of the electric field gradient at the Ni sites. The angle θ is (12±4)° above 30 K and (21±6)° below 30 K. The component of Ni spin with the first kind ordering varies smoothly through 30 K. No anomaly has been observed in the isomer shift and the quadrupole splitting at 30 K and at Neel temperature of 54 K. The quadrupole splitting is -(0.27±0.01) mm/sec at 295 K. An effect of u parameter of crystal lattice can explain the negative sign and the weak temperature dependence of the quadrupole splitting of 57 Fe in NiS 2 .
31 citations
TL;DR: In this paper, the magnetic-moment distribution in disordered ferromagnetic bcc ${\mathrm{Fe}}_{3}$Cr has been determined by polarized-neutron diffraction, when compared with those of pure Fe obtained by Shull and co-workers and those for a Fe-Cr alloy of slightly smaller Cr content measured by Lander and Heaton, show an appreciably smaller asphericity.
Abstract: The magnetic-moment distribution in disordered ferromagnetic bcc ${\mathrm{Fe}}_{3}$Cr has been determined by polarized-neutron diffraction. The measured magnetic structure factors, when compared with those of pure Fe obtained by Shull and co-workers and those for a Fe-Cr alloy of slightly smaller Cr content measured by Lander and Heaton, show an appreciably smaller asphericity. The composition dependence of the asphericity has been compared both with a localized-electron model and with calculations based on the coherent-potential approximation (CPA). The concentration dependences of the total spin magnetic moments, of the difference between the magnetic moments of the constituents, and of the density of states at the Fermi level are also compared with the CPA calculations. It is shown that the theory is able to reproduce the general trend of the experimental data in these alloys.
TL;DR: In this article, it was shown that the high temperature magnetic structure is centred tetragonal and true T N = 45.5 K, which is a first order transition temperature at which helimagnetic macrodomains break into metamagnetic microdomains.
TL;DR: A new barium ferrite, BaO·2Fe2O3, was found to be crystallized by heating suspension of α-Fe 2O3 in aqueous barium hydroxide solution under hydrothermal conditions at around 260°C.
TL;DR: In this article, the magnetic properties of ThMn2Si2 and Thmn2Ge2 were studied using neutron diffraction, X-ray diffraction and magnetometric techniques.
Abstract: ThMn2Si2 and ThMn2Ge2 were studied using neutron diffraction, X-ray diffraction, and magnetometric techniques. Both the compounds have tetragonal CeAl2Ge2-type structure. Position parameters z for Si and Ge were determined. ThMn2Si2 is an antiferromagnet with a Neel temperature of 483 K, and ThMn2Ge2 exhibits a small ferromagnetic moment of 0.35μB with the Curie temperature of 400 K. The magnetic transition in ThMn2Ge2 is of first order. The magnetic structures for both compounds consist of ferromagnetic layers perpendicular to the c0-axis which are antiferromagnetically coupled to adjacent layers. The magnetic moment direction in ThMn2Si2 is parallel t o the c0-axis, and in ThMn2Ge2 the magnetic moment is slightly deviated from c0-axis. It is suggested that conduction.
[Russian Text Ignore]
TL;DR: In this article, the results of a numerical diagonalization study of the next-nearest neighbor Heisenberg model on the fcc lattice were presented, and the results showed that the antiferromagnetic type-II order penetrates into the ferromagnetic area of the mean-field model.
Abstract: We present the results of a numerical diagonalization study of the next-nearest neighbour Heisenberg model on the fcc lattice. We have studied clusters of s = 1/2 spins of sizes N = 32 and 64 and obtained ground state energy, magnetization, susceptibility, and static structure factor for various values of applied fields and interaction parameters. From the magnetic structure factors, we find that the antiferromagnetic type-II order penetrates into the ferromagnetic area of the mean-field model. The magnetisation of the type-II state in this area jumps from zero to totally magnetised at a certain applied field. Other areas containing type-II or type-III order, displays “offsets” in the magnetisation curves. Another anomaly is that the phase boundary between the type-I and the type-III states moves in favour of the type-I state around half magnetisation. Apart from this, the phase boundaries are located at their mean field values at zero field, and the positions of the phase boundaries do not depend on the field value. By comparing the longitudinal and transverse structure factors, it is found that the spin orientation in the type-I structure at intermediate fields shows a transition between a canted spin-flop-like structure and a collinear “up-up-up-down” structure. This confirms earlier theoretical predictions. However, in the type-II and type-III phases only the spin-flop structures are observed.
TL;DR: In this article, the magnetic properties of PrZn and NdZn compounds are studied by magnetic measurements and neutron diffraction, and the crystal field parameters are found coherent in sign with those of the heavy rare earth compounds.
Abstract: The magnetic properties of PrZn and NdZn compounds are studied by magnetic measurements and neutron diffraction. Both compounds are antiferromagnetic below 52 and 70 K, respectively. The ordered moments are reduced to 2.35 and 2.55 μB at low temperatures by crystal field effects. Dilatometric measurements reveal a large tetragonal distortion, arising at the Neel temperature and reaching 1.4% at 4.2 K in PrZn. The crystal field parameters are found coherent in sign with those of the heavy rare earth compounds. In PrZn, the magnetostriction is sufficient to explain the fourfold direction of the moment. The ambiguities on the magnetic structure are discussed.
TL;DR: In this article, the magnetic properties of the compound SrTb2Fe2O7 (space group P4 2 mnm ) have been investigated by magnetic measurements of susceptibility and magnetization and by neutron diffraction.
TL;DR: In this article, the magnetic structure of KMnF 3 has been deduced from group-theoretical consideration based on the new space group P 4/m b m, and the proposed structures are examined by trying an interpretation of the magnetic torsion curves given by Heeger et al.
Abstract: The magnetic structure of KMnF 3 has been deduced from group-theoretical consideration based on the new space group P 4/ m b m . In the uniaxial antiferromagnetic region, the structure is of the G-type with the sublattice magnetization parallel to the z axis, while in the weak-ferromagnetic region the structure is of the pseudo-G-type with the sublattice magnetization nearly parallel to the x (or y ) axis and slightly canted towards the y (or x ) axis. These proposed structures are examined by trying an interpretation of the magnetic torsion curves given by Heeger et al. [Phys. Rev. 123 (1961) 1652]. By taking the crystallographic and magnetic domain structures into account, it is shown that the new magnetic structures are fully consistent with the torsion curves including the magnetic-field dependence.
TL;DR: In this paper, Mossbauer spectroscopy of the Fe 2− x Mn x As series confirms that the iron atom completely occupies site I of the structure and leads to Neel temperatures in aggeement with those deduced from magnetic susceptibility measurements.
TL;DR: In this article, an extensive study has been made of the intermediate state in single crystals of superconducting mercury, and a regular laminar structure, closely approaching that envisaged by Landau, was realized in the thinnest sample examined (47 Μm).
Abstract: Using the magneto-optic technique, an extensive study has been made of the intermediate state in single crystals of superconducting mercury. A regular laminar structure, closely approaching that envisaged by Landau, was realized in the thinnest sample examined (47 Μm). The field dependence of the lamina periodicity displays excellent agreement with the Landau model and the deduced surface energy is in good agreement with the Ginzburg-Landau theory. At applied magnetic fields very close to the critical one, the stable magnetic structure consists of isolated superconducting filaments. A number of observations are reported on their growth and stability.
TL;DR: The magnetic structure of ferrimagnetic ilmenite Ni2+Mn4+O3 has been investigated by neutron diffraction as mentioned in this paper, where the spins are oriented into two kinds of ferromagnetic planes perpendicular to the [111] rhomboedral axis.
TL;DR: The magnetic structures and magnitudes of the ordered magnetic moments for hexagonal ternary U2N2M-type compounds have been determined by neutron diffraction as discussed by the authors, where M is P, As, S, Se, Se.
Abstract: The magnetic structures and the magnitudes of the ordered magnetic moments for the hexagonal ternary U2N2M-type compounds (where M is P, As, S, Se) have been determined by neutron diffraction. In U2N2S and U2N2Se the observed magnetic unit cells have the same size as the chemical ones while in U2N2P and U2N2As the magnetic unit cell is doubled along the c-axis. At 4K the magnetic moments on the uranium ion amount to 1.4, 1.7, 1.6 and 2.3 mu B for U2N2S, U2N2P, U2N2As and U2N2Se, respectively. In all of them the direction of the magnetic moment is along the c-axis.
TL;DR: The spin arrangement in antiferromagnetic Ni I2 (TN = 75° K) was determined by the Mossbauer effect in 129I as discussed by the authors, where the combined electric quadrupole and magnetic dipole interactions at T < TN was found that the angle θ formed between the [111] axis and the effective magnetic field acting at the 129I nucleus is 55 ± 90°.
TL;DR: In this paper, a powder sample of the compound CoGeO3 of the orthoperoxene enstatite polytype was studied by neutron diffraction, and it was found that the compound undergoes a transition to antiferromagnetism at TN = = (32 ± 1) °K.
Abstract: A powder sample of the compound CoGeO3 of the orthoperoxene enstatite polytype was studied by neutron diffraction. This compound is paramagnetic at room temperature and its structure belongs to the space group D152h–Pbca, with 16 formula units per unit cell. It is found that the compound undergoes a transition to antiferromagnetism at TN = = (32 ± 1) °K. Two distinctly different magnetic structures C (Pbc'a) and C (Pbca') are equally consistent with the neutron diffraction pattern obtained at 4.2 °K. The magnitudes of the magnetic moment at 4.2 °K are (2.84 ± 0.15) μB and (2.86 ± 0.15) μB for the two structures, respectively. The intensity-temperature curve of the strongest magnetic reflection exhibits a smooth temperature dependence but falls considerably above the Co2+ Brillouin curve (J = 3/2). The six coordinates of the Co2+ ions in the unit cell are also determined from the pattern at 4.2 °K.
TL;DR: The mechanism and experimental arrangement by which magnetic contrast can be observed from materials of cubic anisotropy are indicated in this article, where Fe-3.2Si is used as an example to illustrate the effects of tensile strain, magnetic field switching and residual stress on magnetic structure.
Abstract: The mechanism and experimental arrangement by which magnetic contrast can be observed from materials of cubic anisotropy are indicated. Transformer alloy Fe-3.2Si is used as an example to illustrate the effects of tensile strain, magnetic field switching, residual stress, and inclusions on magnetic structure.
TL;DR: In this paper, the susceptibility of the weak ferromagnet Fe 3 BO 6 has been measured along the principal orthorhombic axes as a function of temperature for T 293 K.
Abstract: The susceptibility of the weak ferromagnet Fe 3 BO 6 has been measured along the principal orthorhombic axes as a function of temperature for T 293 K. The results show that the spins are parallel to [100] for T T 0 = 415 K and parallel [001] for T T 0 . At room temperature a field of 8.8 T is necessary to rotate the spins from [001] to [100]. The magnetic structure of Fe 3 BO 6 is discussed with the aid of representation analysis.
01 Jan 1975
TL;DR: The basic principles of electron exchange are covered first and applied to optical transitions in ion pairs as discussed by the authors, and the Frenkel exciton theory of molecular crystals is applied to magnetic crystals.
Abstract: The basic principles of electron exchange are covered first and applied to optical transitions in ion pairs. The Frenkel exciton theory of molecular crystals is developed and applied to magnetic crystals. The electronic and magnetic structure of magnetic insulators is reviewed, including aspects of most importance to the optical properties of these substances. Finally, a review of several systems such as MnF2 is given.
TL;DR: In this paper, the magnetic behavior of TmxDy1−xFeO3 (x = 0.3, 0.5; 0.7; 1.0) single crystals in the temperature range 90-4.2° K were investigated.