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Giles-Donovan N, Hillier AD, Ishida K, Hampshire BV, Giblin SR, Roessli B, Gehring PM, Xu G, Li X, Luo H, Cochran S, Stock C. Magnetic skin effect in Pb(Fe _{1/2}$Nb _{1/2}$)O 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:435802. [PMID: 39025119 DOI: 10.1088/1361-648x/ad6523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Accepted: 07/18/2024] [Indexed: 07/20/2024]
Abstract
Relaxor-ferroelectrics display exceptional dielectric properties resulting from the underlying random dipolar fields induced by strong chemical inhomogeneity. An unusual structural aspect of relaxors is a skin-effect where the near-surface region in single crystals exhibit structures and critical phenomena that differ from the bulk. Relaxors are unique in that this skin effect extends over a macroscopic lengthscale of ∼100 μmwhereas usual surface layers only extend over a few unit cells (or ∼nm). We present a muon spectroscopy study of Pb(Fe_{1/2}Nb_{1/2})O3(PFN) which displays ferroelectric order, including many relaxor-like dielectric properties such as a frequency broadened dielectric response, and antiferromagnetism with spatially short-range polar correlations and hence can be termed a multiferroic. In terms of the magnetic behavior determined by the Fe3+(S=5/2,L ≈ 0) ions, PFN has been characterized as a unique example of a 'cluster spin-glass'. We use variable momentum muon spectroscopy to study the depth dependence of the slow magnetic relaxations in a large 1 cm3crystal of PFN. Zero-fieldpositivemuon spin relaxation is parameterized using a stretched exponential, indicative of a distribution of relaxation rates of the Fe3+spins. This bandwidth of frequencies changes as a function of muon momentum, indicative of a change in the Fe3+relaxation rates as a function of muon implantation depth in our single crystal. Usingnegativemuon elemental analysis, we find small-to-no measurable change in the Fe3+/Nb5+concentration with depth implying that chemical concentration alone cannot account for the change in the relaxational dynamics. PFN displays an analogous magnetic skin effect reported to exist in the structural properties of relaxor-ferroelectrics.
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Affiliation(s)
- N Giles-Donovan
- Centre for Medical and Industrial Ultrasonics, James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - A D Hillier
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
| | - K Ishida
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
- RIKEN Nishina Center, RIKEN, Wako, Saitama, Japan
| | - B V Hampshire
- ISIS Facility, Rutherford Appleton Laboratory, Harwell, Didcot, United Kingdom
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - S R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - B Roessli
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut (PSI), 5232 Villigen PSI, Switzerland
| | - P M Gehring
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6100, United States of America
| | - G Xu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6100, United States of America
| | - X Li
- Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, People's Republic of China
| | - H Luo
- Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, People's Republic of China
| | - S Cochran
- Centre for Medical and Industrial Ultrasonics, James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - C Stock
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
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Characterization of a Continuous Muon Source for the Non-Destructive and Depth-Selective Elemental Composition Analysis by Muon Induced X- and Gamma-rays. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12052541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The toolbox for material characterization has never been richer than today. Great progress with all kinds of particles and interaction methods provide access to nearly all properties of an object under study. However, a tomographic analysis of the subsurface region remains still a challenge today. In this regard, the Muon Induced X-ray Emission (MIXE) technique has seen rebirth fueled by the availability of high intensity muon beams. We report here a study conducted at the Paul Scherrer Institute (PSI). It demonstrates that the absence of any beam time-structure leads to low pile-up events and a high signal-to-noise ratio (SNR) with less than one hour acquisition time per sample or data point. This performance creates the perspective to open this technique to a wider audience for the routine investigation of non-destructive and depth-sensitive elemental compositions, for example in rare and precious samples. Using a hetero-structured sample of known elements and thicknesses, we successfully detected the characteristic muonic X-rays, emitted during the capture of a negative muon by an atom, and the gamma-rays resulting from the nuclear capture of the muon, characterizing the capabilities of MIXE at PSI. This sample emphasizes the quality of a continuous beam, and the exceptional SNR at high rates. Such sensitivity will enable totally new statistically intense aspects in the field of MIXE, e.g., elemental 3D-tomography and chemical analysis. Therefore, we are currently advancing our proof-of-concept experiments with the goal of creating a full fledged permanently operated user station to make MIXE available to the wider scientific community as well as industry.
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Stock C, Songvilay M, Gehring PM, Xu G, Roessli B. Broadband critical dynamics in disordered lead-based perovskites. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:374012. [PMID: 32252031 DOI: 10.1088/1361-648x/ab86ee] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
Materials based on the cubic perovskite unit cell continue to provide the basis for technologically important materials with two notable recent examples being lead-based relaxor piezoelectrics and lead-based organic-inorganic halide photovoltaics. These materials carry considerable disorder, arising from site substitution in relaxors and molecular vibrations in the organic-inorganics, yet much of our understanding of these systems derives from the initial classic work of Prof. Roger A Cowley, who applied both theory and neutron scattering methods while at Chalk River Laboratories to the study of lattice vibrations in SrTiO3. Neutron scattering continues to play a vital role in characterizing lattice vibrations in perovskites owing to the simple cross section and the wide range of energy resolutions achievable with current neutron instrumentation. We discuss the dynamics that drive the phase transitions in the relaxors and organic-inorganic lead-halides in terms of neutron scattering and compare them to those in phase transitions associated with a 'central peak' and also a soft mode. We review some of the past experimental work on these materials and present new data from high-resolution time-of-flight backscattering spectroscopy taken on organic-inorganic perovskites. We will show that the structural transitions in disordered lead-based perovskites are driven by a broad frequency band of excitations.
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Affiliation(s)
- C Stock
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - M Songvilay
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - P M Gehring
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States of America
| | - Guangyong Xu
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States of America
| | - B Roessli
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), 5232 Villigen PSI, Switzerland
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