Handbook on The Physics and Chemistry of Rare Earths, 1988
Publisher Summary This chapter discusses some of the major milestones reached as theoretical and ... more Publisher Summary This chapter discusses some of the major milestones reached as theoretical and experimental investigations of the rare earths have proceeded intensely since about the early 1950s. This review is in no way intended to be comprehensive. In the study of lanthanide magnetism, neutron scattering (both elastic and inelastic) has played a seminal role in elucidating the complex nature of the magnetic interactions, and thus much of the discussion here will focus on results obtained by these techniques and how they relate to those observed by more conventional bulk experimental tools. The lanthanide metals offer possibly the best known examples of truly local-moment magnetic systems. The complexity of the magnetism in lanthanides lies not in the intrinsic nature of the local moment but rather in the exchange coupling mechanisms that produce the long-range order of the 4f moments, and in the associated properties of anisotropy and magnetostriction that strongly perturb the m...
Abstract Powder neutron diffraction measurements have been carried out on the intermetallic compo... more Abstract Powder neutron diffraction measurements have been carried out on the intermetallic compound DyFe 3 at 4 and 295 K. A modified Rietveld profile refinement program was used to fit the neutron data. It was found that a non-collinear magnetic structure model in the a - c plane, gives a satisfactory fit to the data measured at 4 and 295 K. At 4 K, the iron moments on the three crystallographically non-evuivalent sites lie at 253.6° to the c avis, having a magnitude of 2.2 μ B ; the dysprosium moments on the two non-evuivalent sites lie at 71.8° and 51.5° to the c -avis, having magnitudes of 9.8 μ B and 9.6 μ b , respectively. At 295 K, the moments of iron, Dy 1 , and Dy 11 are reduced to 1.9 μ B , 6.9 μ B , and 6.5 μ B , respectively, and all these moments lie closer to the basal plane than at the lower temperature. The magnetivation per formula unit of the refined structure, 3.8 μ B , is in good agreement with the evperimental value. The orientation of the iron moments determined from the neutron data is compared with the results of a Mossbauer spectrum study of the compound.
Rare earth oxysulfides (RO),S combine with different metal sulfides to form quaternary compounds ... more Rare earth oxysulfides (RO),S combine with different metal sulfides to form quaternary compounds displaying original structures. Some of them have true three-dimensional networks, in which the two non-metals are bonded to the two metals, without selectivity in these bonds. They are for example RCrSZO
... DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Cr... more ... DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Crow, and T. Mihalisin, Phys. Rev. ... [5]DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Crow and T. Mihalisin, Phys. Rev. ...
Neutron diffraction studies of eleven compounds across the compositional range of the Y6(Fe1−xMnx... more Neutron diffraction studies of eleven compounds across the compositional range of the Y6(Fe1−xMnx)23 system reveal the presence of substantial preferential atomic ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range, Mn atoms prefer to occupy the f2 site and Fe atoms the f1 site. Neutron diffraction profile refinements show no long range magnetic ordering occurring in the compositional range from x = 0.4 to 0.75 as a consequence of the sharply reduced exchange interactions in the ternary compounds. The average Fe moments on each of the sites are reduced in the Fe-rich ternaries. The manganese atoms are nonmagnetic. In the Mn-rich ternaries the Fe atoms have no spontaneous moments and the Mn moments are decreased dramatically from Y6Mn23.
The Lujan Center, part of the LANSCE accelerator complex at Los Alamos National Laboratory, opera... more The Lujan Center, part of the LANSCE accelerator complex at Los Alamos National Laboratory, operates a comprehensive neutron scattering facility for the U.S. Department of Energy that serves approximately 300 users per year. This paper will discuss the current instruments and status of the facility and also focus on the plans for a major upgrade of the Center including new instruments and enhancements to specific existing instruments. The instrument suite currently includes two reflectometers (one with full polarization), an engineering diffraction machine, a diffractometer specialized to pair-distribution analysis, 2 general purpose powder diffractometers, and 2 inelastic spectrometers. To complement these spectrometers, a full range of pressure, temperature, and magnetic field sample environments is available for users. As part of the planning for a forthcoming enhancement of Lujan Center, a series of workshops have been held over the past year to encourage user input to the desig...
The magnetic properties of the rare-earth metals and a number of the alloy and compound systems f... more The magnetic properties of the rare-earth metals and a number of the alloy and compound systems formed with rare earths are discussed. Emphasis is placed on current experimental results of bulk magnetic measurements and related transport phenomena and their bearing on theoretical studies. Topics covered include exchange interactions, magnetization processes, crystal field effects and anisotropy, magnetostriction, spin structures and their field dependence, specific heat, optical effects, resistivity, magnetoresistivity, and other transport properties affected by the magnetic order. Examples are drawn from a number of material systems including ionic compounds, solid solution compounds (e.g., rare-earth magnetic semiconductors), intermetallic compounds (permanent magnet materials, etc.), and bubble domain materials in addition to the rare-earth elements and intra-rare-earth alloys. Tables are presented giving the spin structures, ordering temperatures, saturation and effective moments, and other properties of the elements and specific compounds.
It was expected that the conference would provide a forum for critical examination and review of ... more It was expected that the conference would provide a forum for critical examination and review of the current and important trends in rare earth science and technology. To this end, over 170 papers were presented in both oral and poster sessions by researchers representing some nineteen countries. The program committee was particularly gratified to see the diversity of effort being devoted to rare earth research by different disciplines allover the world. The collection of refereed papers in this volume attests to the fact that the objectives of the program committee were indeed realized.
Handbook on The Physics and Chemistry of Rare Earths, 1988
Publisher Summary This chapter discusses some of the major milestones reached as theoretical and ... more Publisher Summary This chapter discusses some of the major milestones reached as theoretical and experimental investigations of the rare earths have proceeded intensely since about the early 1950s. This review is in no way intended to be comprehensive. In the study of lanthanide magnetism, neutron scattering (both elastic and inelastic) has played a seminal role in elucidating the complex nature of the magnetic interactions, and thus much of the discussion here will focus on results obtained by these techniques and how they relate to those observed by more conventional bulk experimental tools. The lanthanide metals offer possibly the best known examples of truly local-moment magnetic systems. The complexity of the magnetism in lanthanides lies not in the intrinsic nature of the local moment but rather in the exchange coupling mechanisms that produce the long-range order of the 4f moments, and in the associated properties of anisotropy and magnetostriction that strongly perturb the m...
Abstract Powder neutron diffraction measurements have been carried out on the intermetallic compo... more Abstract Powder neutron diffraction measurements have been carried out on the intermetallic compound DyFe 3 at 4 and 295 K. A modified Rietveld profile refinement program was used to fit the neutron data. It was found that a non-collinear magnetic structure model in the a - c plane, gives a satisfactory fit to the data measured at 4 and 295 K. At 4 K, the iron moments on the three crystallographically non-evuivalent sites lie at 253.6° to the c avis, having a magnitude of 2.2 μ B ; the dysprosium moments on the two non-evuivalent sites lie at 71.8° and 51.5° to the c -avis, having magnitudes of 9.8 μ B and 9.6 μ b , respectively. At 295 K, the moments of iron, Dy 1 , and Dy 11 are reduced to 1.9 μ B , 6.9 μ B , and 6.5 μ B , respectively, and all these moments lie closer to the basal plane than at the lower temperature. The magnetivation per formula unit of the refined structure, 3.8 μ B , is in good agreement with the evperimental value. The orientation of the iron moments determined from the neutron data is compared with the results of a Mossbauer spectrum study of the compound.
Rare earth oxysulfides (RO),S combine with different metal sulfides to form quaternary compounds ... more Rare earth oxysulfides (RO),S combine with different metal sulfides to form quaternary compounds displaying original structures. Some of them have true three-dimensional networks, in which the two non-metals are bonded to the two metals, without selectivity in these bonds. They are for example RCrSZO
... DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Cr... more ... DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Crow, and T. Mihalisin, Phys. Rev. ... [5]DW Cooke, RS Kwok, RL Lichti, TR Adams, C. Boekema, WK Dawson, A. Kebede, J. Schwegler, JE Crow and T. Mihalisin, Phys. Rev. ...
Neutron diffraction studies of eleven compounds across the compositional range of the Y6(Fe1−xMnx... more Neutron diffraction studies of eleven compounds across the compositional range of the Y6(Fe1−xMnx)23 system reveal the presence of substantial preferential atomic ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range, Mn atoms prefer to occupy the f2 site and Fe atoms the f1 site. Neutron diffraction profile refinements show no long range magnetic ordering occurring in the compositional range from x = 0.4 to 0.75 as a consequence of the sharply reduced exchange interactions in the ternary compounds. The average Fe moments on each of the sites are reduced in the Fe-rich ternaries. The manganese atoms are nonmagnetic. In the Mn-rich ternaries the Fe atoms have no spontaneous moments and the Mn moments are decreased dramatically from Y6Mn23.
The Lujan Center, part of the LANSCE accelerator complex at Los Alamos National Laboratory, opera... more The Lujan Center, part of the LANSCE accelerator complex at Los Alamos National Laboratory, operates a comprehensive neutron scattering facility for the U.S. Department of Energy that serves approximately 300 users per year. This paper will discuss the current instruments and status of the facility and also focus on the plans for a major upgrade of the Center including new instruments and enhancements to specific existing instruments. The instrument suite currently includes two reflectometers (one with full polarization), an engineering diffraction machine, a diffractometer specialized to pair-distribution analysis, 2 general purpose powder diffractometers, and 2 inelastic spectrometers. To complement these spectrometers, a full range of pressure, temperature, and magnetic field sample environments is available for users. As part of the planning for a forthcoming enhancement of Lujan Center, a series of workshops have been held over the past year to encourage user input to the desig...
The magnetic properties of the rare-earth metals and a number of the alloy and compound systems f... more The magnetic properties of the rare-earth metals and a number of the alloy and compound systems formed with rare earths are discussed. Emphasis is placed on current experimental results of bulk magnetic measurements and related transport phenomena and their bearing on theoretical studies. Topics covered include exchange interactions, magnetization processes, crystal field effects and anisotropy, magnetostriction, spin structures and their field dependence, specific heat, optical effects, resistivity, magnetoresistivity, and other transport properties affected by the magnetic order. Examples are drawn from a number of material systems including ionic compounds, solid solution compounds (e.g., rare-earth magnetic semiconductors), intermetallic compounds (permanent magnet materials, etc.), and bubble domain materials in addition to the rare-earth elements and intra-rare-earth alloys. Tables are presented giving the spin structures, ordering temperatures, saturation and effective moments, and other properties of the elements and specific compounds.
It was expected that the conference would provide a forum for critical examination and review of ... more It was expected that the conference would provide a forum for critical examination and review of the current and important trends in rare earth science and technology. To this end, over 170 papers were presented in both oral and poster sessions by researchers representing some nineteen countries. The program committee was particularly gratified to see the diversity of effort being devoted to rare earth research by different disciplines allover the world. The collection of refereed papers in this volume attests to the fact that the objectives of the program committee were indeed realized.
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