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Fisk Fest 8/15/01 Spin Fluctuations in U 2 Zn 17 Broholm et al. PRL (1987)
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Past and Future Insights from Neutron Scattering Collin Broholm*
Johns Hopkins University and NIST Center for Neutron Research
Virtues and Limitations of Neutron Scattering
New Sources and Instrumentation
Capabilities of New Instrumentation
Conclusionsik
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* supported by NSF DMR-0074571
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Fisk Fest 8/15/01
Zachary Fisk and Neutron Scattering
More than 70 papers on neutron scattering: Heavy Fermion Systems Kondo Insulators Valence Fluctuating systems High TC superconductors
Neutrons used to probe Magnetic order and Fluctuations Structure and sample quality Thermal Expansion Phonons
Fisk Fest 8/15/01
Spin Fluctuations in U2Zn17
Broholm et al. PRL (1987)
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Fisk Fest 8/15/01
Structure of YbInCu4
d-spacing (A)
Inte
nsity
(103 c
ount
s/s
)
Lawrence et al PRB (1996)
•Contrast between elements with similar Z•Sensitivity to light atoms in heavy matrix
a probe of sample quality
Flux-grown crystal
Fisk Fest 8/15/01
Magnetic Structure of CeRhIn5
Bao et al PRB (2000)
Fisk Fest 8/15/01
Probing Spin Density Distribution
UPt3
U 5f, 6d, and -7f spin polarizationPt polarized as well
UBe13
Only U polarized
Neumann, Brown, et al. Physica B (1991)
Fisk Fest 8/15/01
Electronic Interactions in La2CuO4
Coldea et al PRL (2001)
Fisk Fest 8/15/01
What makes it hard
150 MeV thermal energy per neutron (fission) a factor Z2 less than X-ray scattering Limitations of current instrumentation
dynamics in samples < 1 mm3
dynamics in nano-structured solids Lateral surface structure complex materials with weak signals Signals from impurities at low concentration Spatial and temporal resolution Pressure above 25 GPa
2cr
Fisk Fest 8/15/01
Expanding Applicability of a Powerful Probe
Increase source brightness Increase spectral brightness by cooling neutrons Increase temporal brightness in pulsed neutron source
Improve beam delivery system Match solid angle to wave vector resolution requirements Match bandwidth to energy resolution requirements
Increase solid angle of detection system Position sensitive detectors Crystal analyzer arrays
Fisk Fest 8/15/01
New Instrumentation and Sources
NIST cold source and instrument upgrade 2002-4 HFIR cold source and instrument upgrade 2002 LANSCE source and instrument upgrade 2002 US Spallation Neutron Source 2006 German high flux research reactor 2004 Australian high flux research reactor 2005 Japanese Spallation Neutron Source 2006 European Spallation Neutron Source ? Chinese Advanced Research reactor ?
Instrument Begin E (meV) Condensed Matter Science Enabled
FANS 1999 1-3 Phonon Density of States
Spin Echo 2000 10-5 Flux lattice dynamicsDynamic Correlations in Glasses
Back Scattering 1999 10-3 Critical PhenomenaQuantum Tunelling
Disc Chopper 2001 10-2-1 Quantum Critical phenomenaPhonon density of states
MACS 2004 10-2-1 Structure of fluctuating systemsImpurity dynamicsInelastic Scattering from small samples
New Instruments for CMP at NIST
Fisk Fest 8/15/01
Intensity from Focusing
1428 cm2 PG(002)
MC Simulation Qiu and Broholm (2001)
MACS monochromator
Fisk Fest 8/15/01
Upgraded Neutron Scattering Facilities at HFIR, ORNL
Upgraded Neutron Scattering Facilities at LANSCEInstrument Begin Specification Condensed Matter
Science Enabled HIPPO Powder Diffractometer
2002 0.35%<Q/Q<5% V1 mm3
Structure and Texture of disordered materials
SMARTS eng. Diffractometer
2001 1 mm3<V<1 m3 Residual Strain in Engineered Structures
Protein Crystallography
2001 TOF sorted Laue diffraction
H-positions in Protein Structure
PHAROS Spectrometer
2002 E/E=0.5% 1 meV<E<1 eV
Room T Lattice and Spin Dynamics
ASTERIX reflectometer
2001 Polarized beam Structure of solid and magnetic interfaces
eV Spectrometer
2004 Rep-rate multiplication
Low T Lattice, Spin, and Liquid Dynamics
Fisk Fest 8/15/01
Fisk Fest 8/15/01May 2001 Aug 7 2001
Instrument Begin Specification Condensed Matter Science Enabled
Silicon Backscattering
2006 eV<E<10eV 0.1Å-1<Q<3.8Å-1
Diffusion, tunneling, and solvent dynamics
Vertical Reflectometer
2006 0<Q<7Å-1 R>10-10
Structure of solid and magnetic interfaces
Horizontal Reflectometer
2006 0<Q<0.5 Å-1
R>10-10 Structure of Liquid interfaces
Extended Q SANS
2006 0.004Å-1<Q<12Å-1 Nano-scale solid and solvent structure
Powder Diffraction
2006 0.1%<Q/Q<1.6% V<0.1 cm3
High Resolution Structure
meV-eV Spectrometer
2006 1.5%<E/E<5% 1 meV<E<1 eV
Room T Lattice and Spin Dynamics
eV-meV Spectrometer
2006 3%<E/E<10% 0 meV<E<20 meV
Low T Lattice, Spin, and Liquid Dynamics
Instruments for CMP at SNS
Fisk Fest 8/15/01
Neutrons in the 21 centuryChemical and magnetic structure at the interfaces of nano-
scale artificially structured systemsExcitations in materials patterned on the nano-scaleProtein structure (including D-positions) and dynamicsComplete 4 D Q-E mapping of dynamic correlation
function for spin and lattice in large single crystals 0<E<100 meV
Systematic access to order parameters of weak or complex broken symmetry phases
Inelastic neutron scattering as a super-susceptometer for screening new materials
Parametric and complete information about structure of matter under extreme conditions
Fisk Fest 8/15/01
Conclusions
Neutrons are great but we don’t have enough yet
New sources and instrumentation should produce a renaissance for the technique
New facilities must be easily accessible to non-neutron-experts to broaden the science program
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