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Magnetism and magnetic materials probed with neutron scattering
Author's Accepted Manuscript
Magnetism and Magnetic Materials probed with Neutron Scattering S.G.E. te Velthuis, C. Pappas
www.elsevier.com/locate/jmmm
PII: DOI: Reference:
S0304-8853(13)00693-8 http://dx.doi.org/10.1016/j.jmmm.2013.09.034 MAGMA58541
To appear in:
Journal of Magnetism and Magnetic Materials
Received date: 10 September 2013 Cite this article as: S.G.E. te Velthuis, C. Pappas, Magnetism and Magnetic Materials probed with Neutron Scattering, Journal of Magnetism and Magnetic Materials, http://dx.doi.org/10.1016/j.jmmm.2013.09.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Magnetism and Magnetic Materials probed with Neutron Scattering S.G.E. te Velthuis1,* and C. Pappas2 1
Materials Science Division, Argonne National Laboratory, 9700 S Cass Ave, Argonne, Illinois 60439, USA. 2 Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629JB Delft, The Netherlands
*Corresponding author: [email protected] Abstract Neutron scattering techniques are becoming increasingly accessible to a broader range of scientific communities, in part due to the onset of next-generation, high-power spallation sources, high-performance, sophisticated instruments and data analysis tools. These technical advances also advantageously impact research into magnetism and magnetic materials, where neutrons play a major role. In this Current Perspective series, the achievements and future prospects of elastic and inelastic neutron scattering, polarized neutron reflectometry, small angle neutron scattering, and neutron imaging, are highlighted as they apply to research into magnetic frustration, superconductivity and magnetism at the nanoscale. Keywords Neutron scattering; magnetic frustration; superconductivity; nanostructures; nanocomposites Introduction There is no doubt that neutron scattering plays a significant role in determining and consequently understanding the properties and physical phenomena of materials. This impact is illustrated by recent literature and books that give overviews of neutron scattering [1] as applied to studying condensed matter physics [2] with a focus on magnetism and magnetic systems [3]. The impact of neutron scattering in modern science was recognized through the awarding of the 1994 Nobel Prize in Physics to Bertram N. Brockhouse and Clifford G. Shull, specifically for the development of neutron spectroscopy and the neutron diffraction technique, respectively. A major area of research where these techniques have been applied and proven to be of great use is magnetism, a prospect that was recognized early on. In fact, Clifford Shull published Detection of Antiferromagnetism by Neutron Diffraction [4] in 1949, only a year after the first publication on neutron diffraction [5]. This work showed that magnetic moments can order antiferromagnetically. It was the first direct experimental evidence for this new state of matter and the first confirmation of the theory developed in the 1930s by Louis Néel [6] who received the Nobel Price in 1970. Shull and Smart published the now wellknown, low temperature (80 K) diffraction pattern of MnO, illustrating an additional diffraction peak absent in the pattern taken at room temperature. They argued it was at a position not allowed by the crystal structure and could be indexed to be consistent with a
unit cell that was twice that of the crystal structure, hence indicating antiferromagnetic ordering. Equally important, Bertram Brockhouse published Scattering of Neutrons by Spin Waves in Magnetite [7] in 1957 showing the first experimental data of the energy dispersion of a spin wave in ferrimagnetic Fe3O4, paving the way for studies of magnetic excitations with inelastic neutron scattering. Since these pioneering contributions, new neutron sources, instruments, and techniques have been invented and refined. To highlight some of these developments and achievements, this Current Perspective series gives an overview of the current research in magnetism and the enabling neutron scattering techniques. Included are papers focused on specific research areas, where neutron scattering techniques play a major role, balanced with papers focused on specific techniques depicting how these can be used to study magnetic materials. While crystallographic and magnetic structure information, as can be obtained from diffraction experiments, form the foundation of magnetic materials investigations, the nature of the spin correlations lies at the core of understanding their magnetic behavior. How inelastic neutron scattering studies, that measure magnetic excitations, contribute to obtaining insights into these correlations, is discussed in the perspective by Isabelle Mirebeau and Sylvain Petit [8] for systems that exhibit magnetic frustration, and by John Tranquada et al. [9] for high temperature superconductors. Specifically, Mirebeau and Petit highlight recent achievements in the understanding of magnetic frustration in pyrochlore magnets, multiferroics, and chiral magnets. In both cuprate-based and more recently-discovered iron-pnictide/chalchogenide superconductors, the compositional phase diagram shows that antiferromagnetic order exists next to superconductivity. Consequently, it is generally assumed that antiferromagnetic correlations and fluctuations are important for the mechanisms that lead to superconductivity. However, as discussed by J. Tranquada et al., there is an active debate in the community as to the exact origin and nature of these correlations, driven to a substantial degree by results from neutron scattering experiments. Often, mistakingly, neutron scattering is thought of exclusively as a technique for studying the collective behavior of bulk samples. In fact, techniques such as polarized neutron reflectometry (PNR) and small angle neutron scattering (SANS) have had a large impact [10] and have great potential for studying magnetism at the nanoscale. For nanostructured magnetic materials, M.R. Fitzsimmons and Ivan K. Schuller [11] provide a perspective on how, for the currently most important materials phenomena, PNR and/or SANS can address key outstanding questions. Recent topics of greatest interest, such as the emergent phenomena at the interfaces of heterostructures and the manipulation of magnetism with strain and electric current are considered. Complementarily, the perspective by Andreas Michels et al. [12], elaborates on the development of sophisticated micromagnetic simulations that now enable the interpretation of magnetic SANS experiments from nanocomposite materials. As a result of the improvement of neutron sources over the decades, specifically with respect to their increased flux, and the development of more efficient neutron polarizers,
the imaging of magnetic domains and fields with a useful resolution has become possible. In the final perspective of this series, W. Treimer [13] discusses the different types of instrumentation for imaging that have been developed and how, they have been used to image magnetic fields and subsequently improve understanding of flux pinning and suppressed Meissner effects in superconductors. As pointed out, imaging with neutrons is an area still expanding with respect to the capabilities as well as its applications. Acknowledgements Work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under contract no. DE-AC02-06CH11357. References [1] B. T. M. Willis and C. J. Carlile, Experimental Neutron Scattering, Oxford University Press, Oxford, 2013. [2] Albert Furrer, Joël Mesot, Thierry Strässle, first ed., Neutron scattering in condensed matter physics, World Scientific Publishing Company, 2009. [3] Tapan Chatterji (Ed.) Neutron Scattering from Magnetic Materials, Elsevier B.V., 2006. [4] C.G. Shull and J. Samuel Smart, Phys. Rev. 76 (1949) 1256. [5] E.O. Wollan and C.G. Shull, Phys. Rev. 73 (1948) 830. [6] L. Néel, Ann. de Phys. 18 (1932) 5; Ibid., 5 (1936) 232; Compt. Rend. 203 (1936) 304. [7] B. N. Brockhouse, Phys. Rev. 106 (1957) 859. [8] I. Mirebeau and Sylvain Petit, J. Magn. Magn. Matter, this issue (2013). [9] J.M. Tranquada, G. Xu, and I.A. Zaliznyak, J. Magn. Magn. Matter, this issue (2013). [10] M.R. Fitzsimmons, S.D. Bader, J.A. Borchers, G.P. Felcher, J.K. Furdyna, A. Hoffmann, J.B. Kortright, Ivan K. Schuller, T.C. Schulthess, S.K. Sinha, M.F. Toney, D. Weller, S. Wolf, J. Magn. Magn. Mater. 271 (2004) 103. [11] M.R. Fitzsimmons and I.K. Schuller, J. Magn. Magn. Matter, this issue (2013). [12] A. Michels, S. Erokhin, D. Berkov, and N. Gorn, J. Magn. Magn. Matter, this issue (2013) [13] W. Treimer, J. Magn. Magn. Matter, this issue (2013). Introduction to Current Perspective series titled Magnetism and Magnetic Materials probed with Neutron Scattering.
Highlights Elastic and inelastic neutron scattering in systems with magnetic frustration and superconductivity. Small angle neutron scattering and polarized neutron reflectometry in studying magnetism at the nanoscale. Imaging of magnetic fields and domains.
Magnetism and Magnetic Materials probed with Neutron Scattering S.G.E. te Velthuis, C. Pappas
www.elsevier.com/locate/jmmm
PII: DOI: Reference:
S0304-8853(13)00693-8 http://dx.doi.org/10.1016/j.jmmm.2013.09.034 MAGMA58541
To appear in:
Journal of Magnetism and Magnetic Materials
Received date: 10 September 2013 Cite this article as: S.G.E. te Velthuis, C. Pappas, Magnetism and Magnetic Materials probed with Neutron Scattering, Journal of Magnetism and Magnetic Materials, http://dx.doi.org/10.1016/j.jmmm.2013.09.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Magnetism and Magnetic Materials probed with Neutron Scattering S.G.E. te Velthuis1,* and C. Pappas2 1
Materials Science Division, Argonne National Laboratory, 9700 S Cass Ave, Argonne, Illinois 60439, USA. 2 Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629JB Delft, The Netherlands
*Corresponding author: [email protected] Abstract Neutron scattering techniques are becoming increasingly accessible to a broader range of scientific communities, in part due to the onset of next-generation, high-power spallation sources, high-performance, sophisticated instruments and data analysis tools. These technical advances also advantageously impact research into magnetism and magnetic materials, where neutrons play a major role. In this Current Perspective series, the achievements and future prospects of elastic and inelastic neutron scattering, polarized neutron reflectometry, small angle neutron scattering, and neutron imaging, are highlighted as they apply to research into magnetic frustration, superconductivity and magnetism at the nanoscale. Keywords Neutron scattering; magnetic frustration; superconductivity; nanostructures; nanocomposites Introduction There is no doubt that neutron scattering plays a significant role in determining and consequently understanding the properties and physical phenomena of materials. This impact is illustrated by recent literature and books that give overviews of neutron scattering [1] as applied to studying condensed matter physics [2] with a focus on magnetism and magnetic systems [3]. The impact of neutron scattering in modern science was recognized through the awarding of the 1994 Nobel Prize in Physics to Bertram N. Brockhouse and Clifford G. Shull, specifically for the development of neutron spectroscopy and the neutron diffraction technique, respectively. A major area of research where these techniques have been applied and proven to be of great use is magnetism, a prospect that was recognized early on. In fact, Clifford Shull published Detection of Antiferromagnetism by Neutron Diffraction [4] in 1949, only a year after the first publication on neutron diffraction [5]. This work showed that magnetic moments can order antiferromagnetically. It was the first direct experimental evidence for this new state of matter and the first confirmation of the theory developed in the 1930s by Louis Néel [6] who received the Nobel Price in 1970. Shull and Smart published the now wellknown, low temperature (80 K) diffraction pattern of MnO, illustrating an additional diffraction peak absent in the pattern taken at room temperature. They argued it was at a position not allowed by the crystal structure and could be indexed to be consistent with a
unit cell that was twice that of the crystal structure, hence indicating antiferromagnetic ordering. Equally important, Bertram Brockhouse published Scattering of Neutrons by Spin Waves in Magnetite [7] in 1957 showing the first experimental data of the energy dispersion of a spin wave in ferrimagnetic Fe3O4, paving the way for studies of magnetic excitations with inelastic neutron scattering. Since these pioneering contributions, new neutron sources, instruments, and techniques have been invented and refined. To highlight some of these developments and achievements, this Current Perspective series gives an overview of the current research in magnetism and the enabling neutron scattering techniques. Included are papers focused on specific research areas, where neutron scattering techniques play a major role, balanced with papers focused on specific techniques depicting how these can be used to study magnetic materials. While crystallographic and magnetic structure information, as can be obtained from diffraction experiments, form the foundation of magnetic materials investigations, the nature of the spin correlations lies at the core of understanding their magnetic behavior. How inelastic neutron scattering studies, that measure magnetic excitations, contribute to obtaining insights into these correlations, is discussed in the perspective by Isabelle Mirebeau and Sylvain Petit [8] for systems that exhibit magnetic frustration, and by John Tranquada et al. [9] for high temperature superconductors. Specifically, Mirebeau and Petit highlight recent achievements in the understanding of magnetic frustration in pyrochlore magnets, multiferroics, and chiral magnets. In both cuprate-based and more recently-discovered iron-pnictide/chalchogenide superconductors, the compositional phase diagram shows that antiferromagnetic order exists next to superconductivity. Consequently, it is generally assumed that antiferromagnetic correlations and fluctuations are important for the mechanisms that lead to superconductivity. However, as discussed by J. Tranquada et al., there is an active debate in the community as to the exact origin and nature of these correlations, driven to a substantial degree by results from neutron scattering experiments. Often, mistakingly, neutron scattering is thought of exclusively as a technique for studying the collective behavior of bulk samples. In fact, techniques such as polarized neutron reflectometry (PNR) and small angle neutron scattering (SANS) have had a large impact [10] and have great potential for studying magnetism at the nanoscale. For nanostructured magnetic materials, M.R. Fitzsimmons and Ivan K. Schuller [11] provide a perspective on how, for the currently most important materials phenomena, PNR and/or SANS can address key outstanding questions. Recent topics of greatest interest, such as the emergent phenomena at the interfaces of heterostructures and the manipulation of magnetism with strain and electric current are considered. Complementarily, the perspective by Andreas Michels et al. [12], elaborates on the development of sophisticated micromagnetic simulations that now enable the interpretation of magnetic SANS experiments from nanocomposite materials. As a result of the improvement of neutron sources over the decades, specifically with respect to their increased flux, and the development of more efficient neutron polarizers,
the imaging of magnetic domains and fields with a useful resolution has become possible. In the final perspective of this series, W. Treimer [13] discusses the different types of instrumentation for imaging that have been developed and how, they have been used to image magnetic fields and subsequently improve understanding of flux pinning and suppressed Meissner effects in superconductors. As pointed out, imaging with neutrons is an area still expanding with respect to the capabilities as well as its applications. Acknowledgements Work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under contract no. DE-AC02-06CH11357. References [1] B. T. M. Willis and C. J. Carlile, Experimental Neutron Scattering, Oxford University Press, Oxford, 2013. [2] Albert Furrer, Joël Mesot, Thierry Strässle, first ed., Neutron scattering in condensed matter physics, World Scientific Publishing Company, 2009. [3] Tapan Chatterji (Ed.) Neutron Scattering from Magnetic Materials, Elsevier B.V., 2006. [4] C.G. Shull and J. Samuel Smart, Phys. Rev. 76 (1949) 1256. [5] E.O. Wollan and C.G. Shull, Phys. Rev. 73 (1948) 830. [6] L. Néel, Ann. de Phys. 18 (1932) 5; Ibid., 5 (1936) 232; Compt. Rend. 203 (1936) 304. [7] B. N. Brockhouse, Phys. Rev. 106 (1957) 859. [8] I. Mirebeau and Sylvain Petit, J. Magn. Magn. Matter, this issue (2013). [9] J.M. Tranquada, G. Xu, and I.A. Zaliznyak, J. Magn. Magn. Matter, this issue (2013). [10] M.R. Fitzsimmons, S.D. Bader, J.A. Borchers, G.P. Felcher, J.K. Furdyna, A. Hoffmann, J.B. Kortright, Ivan K. Schuller, T.C. Schulthess, S.K. Sinha, M.F. Toney, D. Weller, S. Wolf, J. Magn. Magn. Mater. 271 (2004) 103. [11] M.R. Fitzsimmons and I.K. Schuller, J. Magn. Magn. Matter, this issue (2013). [12] A. Michels, S. Erokhin, D. Berkov, and N. Gorn, J. Magn. Magn. Matter, this issue (2013) [13] W. Treimer, J. Magn. Magn. Matter, this issue (2013). Introduction to Current Perspective series titled Magnetism and Magnetic Materials probed with Neutron Scattering.
Highlights Elastic and inelastic neutron scattering in systems with magnetic frustration and superconductivity. Small angle neutron scattering and polarized neutron reflectometry in studying magnetism at the nanoscale. Imaging of magnetic fields and domains.