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  • 1
    Electronic Resource
    Electronic Resource
    Spin density waves in dilute CuMn alloys : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5454-5456 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron scattering studies on concentrated CuMn alloys show static spin density waves (SDW) that are incommensurate with the lattice and which become dynamic above the freezing temperature Tf with a dispersion relation that is essentially vertical. The existence of both the static and the dynamic SDW in dilute CuMn alloys where the Mn atoms may be separated beyond the range of SDW stability was examined. There is no such cutoff range in the Overhauser SDW model where the transition temperature is simply linear with concentration, but a recent calculation by Ioffe and Feigel'man gives magnetic order that does depend on an interaction range and the density of spins on the lattice. For CuMn alloys, they obtain spin-glass ordering at low Mn concentration with a crossover to short-range helical order near 10% Mn. Our neutron scattering measurements were made on single crystals of CuMn alloys containing 1.4% and 3.0% Mn. Elastic scans along 〈1ζ0〉 at temperatures well below Tf yield the same type of intensity distribution as that previously observed for the more concentrated alloys and show the existence of static SDW at dilutions down to 1.4% Mn. Inelastic scans in the same Q region for the Cu–3% Mn alloy clearly show the presence of dynamic SDW at temperatures up to T/Tf=7.5. These results favor the SDW model of Overhauser as the best description of the magnetic order in dilute CuMn alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353716
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  • 2
    Electronic Resource
    Electronic Resource
    Structure of the modulated magnetic phase of Mn3Sn (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6601-6601 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intermetallic compound Mn3Sn has the hexagonal DO19 crystal structure with six Mn and two Sn atoms per unit cell. The triangular antiferromagnetic order that develops below TN=420 K becomes modulated below 270 K in what is generally described as a helical modulation. However, magnetic excitation spectra show the presence of an energy gap of about 4 meV for both the triangular and the modulated phases, and this can occur for a helical modulation only if the period is commensurate with the lattice. This prompted us to re-examine the structure of the modulated phase by neutron diffraction. We find two distinct moment modulations, both propagating along the c axis and both of which are commensurate below 120 K with periods of 11c0 and 14c0. Above 120 K, both modulation wave vectors increase with temperature and become incommensurate. The satellite reflections exhibit quite different intensities and temperature dependencies, and this suggests coexistent modulated phases. For the predominant 11c0 (22 layer) phase, we observe a third harmonic with about 20% of the amplitude of the first harmonic and with no fifth harmonic to 1% in amplitude. This shows that the modulation in Mn3Sn is definitely not that of a uniform helix. The observed intensity distributions are compared with configurational models in which multilayer blocks of the triangular order align along the easy sixfold axes in the basal plane and rotate by 60° per block in proceeding along the c axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356908
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic transitions at high fields in (Fe,Mn)3Si alloys : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6359-6361 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the series of ordered DO3 solid solutions Fe3−xMnxSi, field-induced transitions have previously been found to occur for antiferromagnetic alloys with values of x near 1.70. The present work has determined a region of composition in which antiferromagnetism is the low-field, low-temperature state and gives the variation of the critical field as a function of temperature and composition. The critical field decreases approximately quadratically with temperature and rises to beyond 6 T in the range of composition from 1.6≤x≤1.8. Neutron diffraction indicates that the antiferromagnetic axis is shifted from the [111] direction and that in a 5 T field the antiferromagnetic component of the scattering is reduced considerably from that in zero field. However, no corresponding increase in ferromagnetic component is observed within experimental error and Arrott plots suggest the high-field state is still largely antiferromagnetic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358266
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  • 4
    Electronic Resource
    Electronic Resource
    Atomic and magnetic spatial correlations in Fe-13.5% V (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6150-6150 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, considerable theoretical effort has been directed toward a general understanding of the thermally induced concentration and magnetic moment fluctuations in alloys and the relationship of these fluctuations to alloy phase stability. The atom–atom, atom–moment, and moment–moment spatial correlations that are determined from neutron diffuse scattering measurements can be directly compared to those based on electronic structure calculations and thereby provide stringent tests for the theoretical approaches as well as theoretical assistance in the interpretation of experimental results. These comparisons are best made with single crystal data taken along high symmetry directions but surprisingly little of such data is available. In this paper we report the atom–atom and atom–moment correlations along the three highest symmetry directions for the ferromagnetic bcc alloy Fe-13.5% V. These are compared with and are found to be in excellent agreement with predictions from "first-principles'' calculations1 of the same correlation functions.〈ks〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348787
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  • 5
    Electronic Resource
    Electronic Resource
    Extreme covalence in the Tc–Cl bond from polarized neutron diffraction (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7743-7745 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A polarized neutron diffraction experiment on a salt containing the 4d1 TcNCl4− ion (S=1/2) yielded the flipping ratios of six reflections confined to the hk0 plane. Using nuclear structure factors, FN, extrapolated from the 123 and 295 K x-ray structures, magnetic structure factors, FM, were obtained from the flipping ratios. The values of FM were fitted to a model of spin populations in the Tc-4d and the Cl-3(sp) orbitals. It was found that 46(5)% of the spin density is located on the Cl atoms, corresponding to exceptionally high covalence in the Tc–Cl bonding. The amount is distinctly higher than found indirectly by ESR measurements, but is to some extent supported by a local density functional DV–Xα calculation. Because the data is limited to the one projection, it is not possible to separate the Tc and N spin density contributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464581
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic rare-earth superlattices (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3447-3452 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic structures of several single-crystal, magnetic rare-earth superlattice systems grown by molecular-beam epitaxy are reviewed. In particular, the results of recent neutron diffraction investigations of long-range magnetic order in Gd-Y, Dy-Y, Gd-Dy, and Ho-Y periodic superlattices are presented. In the Gd-Y system, an antiphase domain structure develops for certain Y layer spacings, whereas modified helical moment configurations are found to occur in the other systems, some of which are commensurate with the chemical superlattice wavelength. References are made to theoretical interaction mechanisms recently proposed to account for the magnetic states of these novel materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340763
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  • 7
    Electronic Resource
    Electronic Resource
    Polarized neutron diffraction studies of Gd-Y synthetic superlattices (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4055-4057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microscopic magnetic structures of coherent, single-crystal epitaxially grown superlattices consisting of successive bilayers of NGd basal planes of hexagonal-close-packed Gd followed by NY such atomic planes of nonmagnetic Y have been studied by polarized neutron diffraction. It has been found that for NGd=10, either a simple parallel alignment of the ferromagnetic Gd layers or an antiphase domain structure occurs, depending on the number of intervening Y planes in an oscillatory manner. These data are consistent with a RKKY coupling mechanism between Gd layers. In addition to the investigation of the interlayer interactions, measurements of the magnetization profile across the thickness of a Gd layer have been performed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338525
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  • 8
    Electronic Resource
    Electronic Resource
    Separation of crystal-field levels and phonons in Pr dideuteride using polarized neutrons (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3423-3425 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarized neutrons with polarization analysis are used for the first time successfully for distinguishing crystal-electric-field (CEF) excitations from phonons by investigating both the spin-flip and non-spin-flip cross sections. From this, it is shown that the 20 meV peak in Pr dideuteride, observed previously with unpolarized neutrons, arises from CEF excitations. Since this energy is nearly half the value of the CEF level at 41 meV known before, the 20 meV peak is composed of two contributions. At low temperatures it only arises from transitions from the ground state into the 20 meV level. At room temperature, on the other hand, the 20 meV level is thermally populated, so that transitions from the 20 meV into the 41 meV level are also obtained. This leads to the unexpected increase of the intensity of the 20 meV peak at increasing temperatures observed previously. The present result gives a strong contribution to the knowledge of the CEF parameters of the Pr3+ ions in PrD2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338971
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic excitation in CuMn spin glass alloy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3753-3755 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spin dynamics of a spin glass alloy Cu78.7Mn21.3 have been studied by neutron inelastic scattering. Measurements have been made at 20, 150, and 290 K by the constant E mode of operation. Magnetic excitations with rather large energy transfer have been observed around the (1 1/2 0) and the (1 1/2 ±δ 0) magnetic diffuse peak positions above and below the spin freezing temperature (Tf∼90 K). The results indicate the existence of strong space and time correlations of the spins over the temperature range of the measurements. The experimental data are well explained by a model of dynamically fluctuating spin clusters with a broad distribution of relaxation times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334961
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  • 10
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of La0.5Ca0.5MnO3 (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3883-3883 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nuclear and magnetic structures of the perovskite La0.5Ca0.5MnO3 were studied as a function of temperature. At low temperatures this system exhibits charge ordering and a magnetic structure of a charge exchange-type in the a–c plane with a ferromagnetic component along the b axis. At intermediate temperatures there is a purely ferromagnetic phase. In this intermediate ferromagnetic phase we find charge ordering associated with antiferromagnetic short-range order. We find no evidence that would support the existence of a charge ordered purely ferromagnetic structure. ©1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365055
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