Showing papers on "Magnetic structure published in 1982"
TL;DR: In this paper, the properties of magnetic insulators containing orbitally degenerate transition metal ions (Jahn-Teller ions) are discussed and the mutual effects of the orbital ordering and the magnetic properties of corresponding compounds are discussed.
Abstract: The properties of magnetic insulators containing orbitally degenerate transition metal ions (Jahn-Teller ions) are discussed. The Jahn-Teller effect in these insulators causes structural phase transitions, lowers the lattice symmetry, and gives rise to an orbital ordering. Various interactions responsible for these effects are discussed: the electron-lattice, quadrupole-quadrupole, and exchange interactions. The mutual effects of the orbital ordering and the magnetic properties of corresponding compounds are discussed. The exchange interaction in the cases of twofold and threefold orbital degeneracy is discussed. The effect of a magnetic field on the orbital and magnetic structure and the temperature dependence of the exchange interaction are studied. The properties of several representative compounds containing Jahn-Teller ions are discussed.
825 citations
TL;DR: In this paper, the effects of magnetostatic and repulsive particle interactions on the formation of agglomerates in a magnetic fluid were investigated using Monte Carlo techniques, and the dependence on particle size and applied field of the form of the agglomers was studied using a spatial distribution function which allows a quantitative distinction to be made between clusters and anisotropic chain structures.
Abstract: Monte Carlo techniques have been used to investigate the effects of magnetostatic and repulsive particle interactions on the formation of agglomerates in a magnetic fluid The dependence on particle size and applied field of the form of the agglomerates was studied using a spatial distribution function which allows a quantitative distinction to be made between clusters and anisotropic chain structures Magnetization curves have been calculated for magnetic particle sizes varying from 5 to 15 nm with and without magnetostatic interactions For the larger particle sizes, it was found that the initial susceptibility is reduced in the presence of interactions This is associated with the presence of pronounced agglomeration in zero field, where open clusters are formed As the applied field is increased the clusters break up to form long chains aligned in the field direction At intermediate particle sizes, there is evidence of magnetic field induced agglomeration leading to the formation of dimers and trimers preferentially aligned in the field direction The smallest particle size showed little evidence of ordering even in strong applied fields, since thermal disordering dominates the situation
191 citations
TL;DR: In this article, the magnetic structure and weak ferromagnetic magnetism of Mn 3 Sn were studied by polarized neutron diffraction at room temperature and it was shown that the spin structure has a triangular configuration of inverse geometry in the c-plane and the triangle rotates opposite to the rotation of the c -plane field component.
Abstract: The magnetic structure and weak ferromagnetism of Mn 3 Sn were studied by polarized neutron diffraction at room temperature. The flipping ratio was measured for a number of Bragg reflections by rotating the crystal about the scattering vector under a magnetic field of 8 kOe applied perpendicular to the scattering vector. It was found that the spin structure has a triangular configuration of inverse geometry in the c -plane and the triangle rotates opposite to the rotation of the c -plane field component. From the analysis of the anisotropy energy it was shown that the triangle of inverse geometry is stabilized by the Dzyaloshinski-Moriya interaction and the weak ferromagnetic moment appears from the mechanism that each spin in the inverse triangle tilts slightly toward its easy axis. It was also shown that the weak ferromagnetic moment rotates just opposite to the rotation of the triangle.
150 citations
TL;DR: A Mossbauer spectroscopic study on a series of aluminum-substituted hematites, α(Fe1-cAlc)2O3, with c up to 0.32 is reported in this paper.
106 citations
TL;DR: In this paper, Rietveld analyses of room-temperature neutron powder diffraction data for seven Nd2(CoxFe1−x)17 alloys (x = 0, 0.1,0.3,0.,0.5, 0.,7, 0,9, 1) are reported, and the magnetic moments obtained from the data refinements indicate a transition from a low to a high spin state on the d, ǫf, and h sites as Fe is incorporated into the structure; a reverse trend is exhibited by the
Abstract: Rietveld analyses of room‐temperature neutron powder diffraction data for seven Nd2(CoxFe1−x)17 alloys (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) are reported. In the ternary systems we find that the c‐type transition metal sites are preferentially occupied by Fe ions; concomitantly, the d and h sites have Co occupations larger than those predicted by stoichiometry, while the f sites deviate only slightly from random occupation. The magnetic moments obtained from the data refinements indicate a transition from a low to a high spin state on the d, f, and h sites as Fe is incorporated into the structure; a reverse trend is exhibited by the moments on the c site.
102 citations
TL;DR: The crystal and magnetic structures of the Co x Ni 1 − x MnGe compounds have been studied by neutron diffraction experiments Magnetic phase diagram has been constructed as mentioned in this paper, the compounds with the low Co concentration have helicoidal magnetic structure The compounds with large Co concentration are ferromagnets
87 citations
TL;DR: In this paper, the magnetic structure of a weak ferromagnetic Mn 3 Sn has been studied by polarized neutron diffraction at room temperature, and large flipping ratios were observed for the 100 and 110 reflections under application of a magnetic field in the c -plane perpendicular to the scattering vector.
Abstract: The magnetic structure of a weak ferromagnetic Mn 3 Sn has been studied by polarized neutron diffraction at room temperature. Large flipping ratios were observed for the 100 and 110 reflections under application of a magnetic field in the c -plane perpendicular to the scattering vector. The spin structure deduced from the h 0 l and h h l reflections has a triangular configuration but the spin plane is not determined. For applied field parallel to [010] the spin-A is parallel to [010], but for applied field parallel to [\bar110] the spin-B is antiparallel to [\bar110]. The magnetic form factor of the Mn atom agrees with the calculated Mn 2+ form factor and the magnetic moment is 1.78 µ B /Mn.
67 citations
TL;DR: Magnetic properties of the Ce 1- x La x Mn 2 Si 2 system were investigated by means of neutron diffraction and magnetometry in this paper, where it was shown that the type of magnetic ordering depends on the Mn-Mn interatomic distances in the basal plane.
60 citations
TL;DR: In this article, it was shown that the deviation of the magnetic field is a manifestation of the newly-reconnected field line loop loop's draping toward the tail's central or midnight meridian.
Abstract: The magnetic field in the plasmoid which is created by the reconnection of magnetic field lines at a neutral line formed in the near-earth region of the plasma sheet at substorm onset, and which flows out of the magnetotail into the magnetosphere's wake, displays a strong positive or negative Y(SM) component that has been difficult to reconcile with the standard, two-dimensional reconnection geometry. It is shown that this deviation of the magnetic field is a manifestation of the newly-reconnected field line loop's draping toward the tail's central or midnight meridian, and that the draping is a consequence of the three-dimensional plasma flow associated with the reconnection process.
54 citations
45 citations
TL;DR: A powder neutron diffraction study and subsequent line profile analysis of the magnetic structure of iron(III) molybdate at 2 K indicate that it is a four-sublattice antiferromagnet containing four crystallographically distinct iron atoms in the space group P2/sub 1/a (b unique) as discussed by the authors.
Abstract: A powder neutron diffraction study and subsequent line-profile analysis of the magnetic structure of iron(III) molybdate at 2 K indicate that it is a four-sublattice antiferromagnet containing four crystallographically distinct iron atoms in the space group P2/sub 1//a (b unique). An analysis of covalency in iron(III) molybdate reveals a higher degree of covalency (A/sub sigma//sup 2/ + 2A/sub ..pi..//sup 2/ + A/sub s//sup 2/ = 9.15%) in the iron(III) to oxygen bonds than is found in the structurally related iron(III) sulfate (6.1%). A Moessbauer-effect study indicates that, at 11.8 K and above, iron(III) molybdate is paramagnetic with parameters typical of an octahedral high-spin iron(III) compound. Between 11.72 and 11.59 K both ordered and paramagnetic phases coexist. Below 11.72 K the Moessbauer spectrum shows the presence of spontaneous magnetic ordering with four inequivalent magnetic hyperfine fields. On three of the iron sites, the hyperfine fields are rather similar while the fourth site exhibits a significantly greater hyperfine field. The differences between various combinations of the four hyperfine fields show maxima at about 10 K. At 1.14 K the field values are 540, 529, 519, and 509 kOe. The isomer shifts for each site are similar at ca. 0.52 mm/s, and themore » quadrupole shifts are small at ca. +- 0.01 mm/s. Magnetic susceptibility studies confirm that the material is paramagnetic above ca. 20 K, with an effective magnetic moment of 5.92 ..mu../sub B/ and a Curie-Weiss temperature of -55.6 K. The magnetic susceptibility shows a peak of ca. 10 K, the magnitude of which increases with decreasing applied field between 45.81 and 9.95 kG. 8 figures, 2 tables.« less
TL;DR: In this paper, the low-energy part of the ground-state magnetic excitation spectra of Ho2Co17 and Ho2Fe17 were found to consist of three modes: (i) a highly dispersive transition-metal mode; (ii) a non-dispersive local mode and (iii) a weakly dispersive mode degenerate with the local mode at the zone boundary.
Abstract: The low-energy part (<20 meV) of the ground-state magnetic excitation spectra of Ho2Co17 and Ho2Fe17 were found to consist of three modes: (i) a highly dispersive transition-metal mode; (ii) a non-dispersive local mode and (iii) a weakly dispersive mode degenerate with the local mode at the zone boundary. These modes are interpreted within the linear spin wave formalism, using a two-sublattice approximation for the magnetic structure, and taking isotropic exchange and single-ion crystal-field interactions into account. The exchange constants, the anisotropy of the transition-metal sublattice and two linear combinations of the rare-earth crystal-field parameters B20, B40, B60 and B66 are determined by fitting the linear spin wave solution to the observed dispersion relations.
TL;DR: The magnetic structure of small CrO2 particles doped with about 1.2 wt.% 57Fe has been explored by 57Fe Mossbauer spectroscopy as a function of the particle size as discussed by the authors.
Abstract: The magnetic structure of small CrO2 particles doped with about 1.2 wt.% 57Fe has been explored by 57Fe Mossbauer spectroscopy as a function of the particle size. Mossbauer spectra, obtained with a longitudinal magnetic field applied, unambiguously establish that a noncollinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect is the origin of this phenomenon. It follows that a core model proposed earlier for the magnetic structure of CrO2 small particles is warranted.
TL;DR: A noncollinearity of the magnetic structure in HoCo5 during the magnetization reorientation has been evidenced through magnetization Mossbauer and neutron diffraction measurements.
Abstract: A noncollinearity of the magnetic structure in HoCo5 during the magnetization reorientation has been evidenced through magnetization Mossbauer and neutron diffraction measurements. Such a configuration permits a minimization of exchange interactions and holmium and cobalt anisotropies which are competing.
TL;DR: In this article, a spin flop transition occurring in fields of 1-15 kOe at 4.2 K was analyzed in terms of effective anisotropy and exchange fields.
Abstract: Silicates are the most common Earth materials. Many iron‐rich solid solution series order magnetically but ordering temperatures rarely exceed 100 K, even for the iron end‐members. Minerals with sheet and chain structures are discussed, with emphasis on the magnetic properties of greenalite, cronstedtite, biotite, and crocidolite determined by magnetization, susceptibility, and Mossbauer measurements and by magnetic neutron diffraction. The principal magnetic interactions in the ferrous minerals are ferromagnetic, due to near 90° Fe–O–Fe bond angles for edge‐sharing octahedral sites, yet all of them order antiferromagnetically as the ferromagnetic sheets or chains are coupled by relatively weak antiferromagnetic interactions. A spin flop transition occurring in fields of 1–15 kOe at 4.2 K is analyzed in terms of effective anisotropy and exchange fields. Magnetocrystalline anisotropy arises from the Fe2+ ion which is in an orbital singlet 5A1g, lz=0 ground state in an effectively trigonal crystal field. Th...
TL;DR: In this article, the magnetic ordering of ternary borides RRh3B2 (R=La to Gd) is inferred from the high values of the ratio of paramagnetic moment to ordered state moment.
Abstract: Magnetization (4.2 to 300 K) and 11B paramagnetic NMR (77 to 300 K) studies have been carried out on ternary borides RRh3B2 (R=La to Gd). These compounds crystallize in the CeCo3B2‐type structure. From cell volume considerations Ce is in a mixed valent/quadrivalent state while the rest of the rare earth ions are in a trivalent state. With the exception of La and Pr compounds, all other compounds are found to order magnetically. From the high values of the ratio of paramagnetic moment to ordered state moment, the magnetic ordering is inferred to be the itinerant type in CeRh3B2 and EuRh3B2. In Nd and Gd compounds, magnetization data reveal that magnetic ordering is associated with the rare earth sublattice. A complex behavior of magnetization is observed in SmRh3B2. A first order quadrupole split 11B NMR spectrum is observed in Ce, Pr, Nd, and Sm compounds. The boron Knight shift in all these compounds is small and, within the limits of experimental error, scales linearly with susceptibility in Pr and Nd compounds. A temperature independent Knight shift is observed in SmRh3B2, indicating the influence of strong crystal fields.
TL;DR: In this paper, the authors performed 57Fe Mossbauer measurements in the temperature interval between 295 K and 4.2 K and in an external magnetic field on both powder specimen and single crystals of FeP. The results show a nearly temperature independent electric quadrupole interaction strength eQVzz of 1.34 mm/s.
TL;DR: In this paper, the spin correlations in Zn1−cMncTe alloys for several values of c have been studied by neutron powder diffraction as a function of temperature T between 2 and 300 K.
Abstract: The nature of the spin correlations in Zn1−cMncTe alloys for several values of c has been studied by neutron powder diffraction as a function of temperature T between 2 and 300 K. Results have been obtained for c=0.376, 0.565, 0.594, and 0.68. The correlations are weak at low c and high T, but intensify progressively as c increases and/or T decreases. For c as high as 0.68, the experiments do not indicate any phase transition to a fully ordered magnetic structure, but the appearance of broad, intense magnetic diffuse scattering peaks at particular positions suggests a strong tendency towards antiferromagnetic ordering of type III. The results are analyzed in terms of a theory of the magnetic scattering from magnetic ions surrounded by near‐neighbor shells of correlated spins. Comparison is also made with the correlations expected from an ordered type III structure modified by various exponential functions of a correlation length κ(c). Application of a magnetic field up to 2 Tesla to the c=0.594 specimen p...
TL;DR: In this article, the low-temperature magnetic ordering of nonstoichiometric compounds GdD2+x and SmD2 +x was investigated by neutron diffraction and magnetic susceptibility measurements, and it was shown that both the antiferromagnetic structure and the Neel temperature depend strongly on the D concentration.
Abstract: The low‐temperature magnetic ordering of the nonstoichiometric compounds GdD2+x and SmD2+x for ‖x‖<015 has been investigated by neutron diffraction and magnetic susceptibility measurements It is shown, that both the antiferromagnetic structure and the Neel temperature TN depend strongly on the D concentration Both for GdD193 and for SmD185, the magnetic structure is found to be of the type MnO For higher concentrations, the structure becomes incommensurate with the lattice For GdD200, a helical structure with axis along the 〈111〉 direction is observed The angle between the moments in the successive (111) layers is found to be 1638° For GdD193 and GdD200, TN values of 20 K and 155 K, respectively, are obtained For SmD2+x, TN is found to be reduced from 96 K for x = 015 to 80 K for x = 0 and to less than 45 K for x = 015
TL;DR: In this article, the results from an investigation by Mossbauer spectroscopy of approximately 1 at.% 57Fe in NiCl2, NiBr2 and CoI2 are presented.
Abstract: Results from an investigation by Mossbauer spectroscopy of approximately 1 at.% 57Fe in NiCl2, NiBr2, NiI2 and CoI2 are presented. In NiCl2 and NiBr2 the results are satisfactorily analysed by a crystal-field model, and new information concerning the magnetic spin arrangements has been obtained. At all temperatures below TN for NiCl2+57Fe, and at temperatures between TN and 23K for NiBr2+57Fe, the spins are along a hexagonal (210) direction. Below 23K the results from Mossbauer spectra of NiBr2+57Fe are consistent with a different magnetic structure. Optical spectra taken at several temperatures suggest that iron impurities modify the NiBr2 helical arrangement. Mossbauer spectra of NiI2+57Fe show extreme line broadening; possible explanations are discussed. Lastly, in CoI2+57Fe the results are consistent with a magnetic structure in which the spins lie in the basal plane.
TL;DR: Using powder neutron diffraction techniques, this paper examined the magnetic order of the pseudoternary compound Ho(Rh0.3Ir0.7)4B4 below the Neel temperature TN=2.7K.
TL;DR: In this paper, the temperature dependence of small angle neutron scattering in weakly ferromagnetic Ni3Al has been investigated by means of multi-detector small-angle spectrometers at A.E.L. Grenoble.
Abstract: The temperature dependence of small angle neutron scattering in weakly ferromagnetic Ni3Al has been investigated by means of multi‐detector small‐angle spectrometers at A.E.R.E. Harwell and I.L.L. Grenoble. Measurements are reported in three stoichiometric samples with residual resistivity ratios [RRR=ρ(293 K)/ρ(4.2 K)] of up to 40 and in a Ni rich specimen (Ni75.4Al24.6). The cross sections in stoichiometric specimens exhibit an approximately linear rise with temperature well below the Curie point (TC=41±1 K), a peak around TC and a fall approximately proportional to (T−TC)−1 above TC. This behaviour is interpreted in a Ginzburg‐Landau model of magnetic fluctuations involving a single adjustable parameter, from which a spin correlation length around TC and an effective spin‐wave stiffness well below TC may be derived. Finally the possible qualitative features of the overall transverse magnetic fluctuation spectrum of Ni3Al are examined and a simple model is noted which can account for the observed fall i...
TL;DR: In this article, the energy and entropy of a superposition of several modulated spin patterns is calculated from first principles, and the structures which give stationary free energy are identified, and it is shown that in neodymium a double q structure is the most stable.
Abstract: The energy and entropy of a superposition of several modulated spin patterns is calculated from first principles, and the structures which give stationary free energy are identified. The addition of an anisotropic exchange term, of similar form and magnitude to that observed in praseodymium, suggests the conclusion that in neodymium a double q structure should be the most stable. The experimental evidence on neodymium is reviewed and is shown to be rather naturally accounted for by the double q structure, though as yet no conclusive evidence can be offered.
TL;DR: In this article, the authors investigated the magnetic properties of Tb dihydride TbH2+x for −0.05
Abstract: Tb dihydride TbH2+x has been investigated for −0.05
TL;DR: In this paper, it was shown that the magnetization cannot account for the whole Faraday rotation anisotropy and the magneto-optical coefficient of electric dipole type transitions is anisotropic.
Abstract: Faraday rotation has been measured in (Er2.2Y0.8)Fe5O12 crystals in the 11–300‐K temperature range in a magnetic field along the three main crystallographic directions. A strong anisotropy is observed below the compensation temperature, which vanishes at the compensation. The origin of this anisotropy is discussed and it is shown that the magnetization cannot account for the whole Faraday rotation anisotropy and that the magneto‐optical coefficient Ce of electric dipole type transitions is anisotropic. A comparison between (Er2.2Y0.8)IG and pure ErIG results is given. The strong anisotropy is tentatively related to the noncollinear magnetic structure observed below the compensation.
TL;DR: The cubic CsCl-type compounds TmAg and Tm 0.9 AG have been investigated by means of susceptibility and magnetization measurements and of elastic and inelastic neutron scattering experiments.
TL;DR: The magnetic ordering temperatures of the samples with x≥60 increase with Fe content as discussed by the authors, consistent with the small magnetic hyperfine fields observed in the magnetic samples, and the resistivity of the magnetic and nonmagnetic samples show different temperature dependences.
Abstract: Sputtered amorphous FexNb100−x (30≤x≤85) has been studied by Mossbauer spectroscopy and resistivity measurements. The samples with x<60 are nonmagnetic. The magnetic ordering temperatures of the samples with x≥60 increase with Fe content. Small magnetic hyperfine fields are observed in the magnetic samples, consistent with the small Fe moments measured. The resistivity of the magnetic and nonmagnetic samples show different temperature dependences. Only the magnetic samples exhibit a resistivity minimum, indicating a Kondo‐like mechanism.
TL;DR: In this article, a polarized neutron diffraction experiment at 4.2 K was carried out on two NpAs 2 single crystals with different orientations of the crystallographic axes with respect to the magnetic field.
TL;DR: TmCo 2 has a first order magnetic phase transition with in the magnetic phase a ground state J z = 5 and a first excited state Jz = 4 as mentioned in this paper, where the ground state corresponds to the magnetic transition.