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6 Combining High Magnetic Fields with Scattering and Optical Probes
Pages 105-121

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From page 105...
... In this chapter, the committee discusses opportunities for new science through scattering and optical probes of materials at high magnetic fields. Bringing High Magnetic Fields to Neutron and X-ray Scattering Facilities Neutron and X-ray scattering experiments have seen some radical advances since the previous COHMAG review of high field facilities.
From page 106...
... However, critical fields above 15 T are totally inaccessible to even the largest superconducting magnets available at neutron scattering facilities today. • Magnetic critical fluctuations near quantum critical points (QCPs)
From page 107...
... A further feature of FIGURE 6.1  Inelastic neutron study of magnetic excitations near a quantum critical point induced by an applied magnetic field. By applying a transverse magnetic field to the quasi-one-dimensional Ising spin compound CoNb2O6, the system can be driven from a magnetically ordered phase to a nonmagnetic paramagnet.
From page 108...
... In the same time interval, a new user facility that combines a free electron laser and pulsed fields as large as 85 T has become operational in the Dresden High Magnetic Field Labora tory. A new facility is under construction at Helmholtz Zentrum Berlin (HZB)
From page 109...
... Table 6.1 lists the magnetic fields available at selected U.S. facilities, and Table 6.2 lists international scattering facilities.
From page 110...
... Of particular significance are not only the absolute magnitudes H of the fields attained and the duty cycle (for pulsed-field magnets) , but also the H/T ratios, where T is the sample temperature; the direction of the magnetic fields relative to momentum and polarization vectors; apertures and the
From page 111...
... Vertical 1.5-300 JRR3 (Japan) 6 Vertical 1.5-300 6 Horizontal 2-300 5 Vertical 0.05-1 13.5 Vertical RT bore with dilution insert and high-temperature options 10 Vertical RT bore and dilution insert and high-temperature options 5 Vertical 4 K and dilution insert option 30 (pulsed resistive)
From page 112...
... The resulting activity will then prepare the X-ray and neutron communities to properly manage and exploit more ambitious high-field systems such as hybrid and pulsed-field magnets. Conclusion: Neutron and X-ray scattering measurements have played a central role in explicating the behaviors of virtually every class of strongly interacting matter.
From page 113...
... (See the discussion in Chapter 9.) Combining Optical Probes and High Magnetic Fields Magneto-optical experiments provide a powerful set of tools to obtain insights into the properties of materials, and such experiments are often an ideal way to study new physical phenomena.
From page 114...
... Josephson plasmons Correlation gaps in 1D conductors Organics plasmons helicons bi-polarons cyclotron res Vibrational modes Topological phonons Inter-band transitions insulators Tunable Fermi Energy EF Band gap Tunable band gap in bilayer & band parameters Graphene Interband transitions Landau Levels trasitions 1 10 100 1000 10000 cm-1 1 IR wavelength: 1000 µm 100 µm 10 µm FIGURE 6.3  Characteristic energy scales in solids. NOTE: DFG, difference frequency generation; OPA, optical parametric amplifier; QCL, quantum cascade laser.
From page 115...
... Finally, the development of low-loss single-mode fibers and compact optical components (lenses, polarizers, even nanometer-resolution translation stages) have allowed scientists to perform very advanced optical experiments at the highest possible magnetic fields and even at very low temperatures.
From page 116...
... For all of these reasons, the Dresden facility and the Nijmegen high magnetic field labora tory of the EMFL have integrated free electron lasers (FELs) , providing very high intensity, quasi-monochromatic, pulsed or quasi-continuous radiation, in exactly this frequency range, at their facilities.
From page 117...
... Although the very highest fields achievable at NHFML would not be reached at a centralized FEL facility, a significant breadth of scientific phenomena (including magnetic excitations, collective modes in correlated electron systems, lattice vibrations, and band gaps) could be studied even at lower fields.
From page 118...
... Among other applications of high-power-density radiation sources in high magnetic field experiments, one may think of pulse probe experiments in the far IR, sum frequency and second harmonic generation, and spin-echo electron paramagnetic resonance at frequencies and field ranges at least 10 times higher than is possible now. Furthermore, the combination of far-IR radiation with scan ning probe techniques that can position metallic nanometer-sized antennas with subwavelength precision may even allow far-IR spectroscopy of single objects.
From page 119...
... Photon sources in the frequency range 0.5 to 25 THz are of special importance for high-field experiments, as typical frequencies of electron spin resonances and cyclotron resonances fall in this range for fields between 20 and 100 T Recommendation: A full photon spectrum, covering at least all of the ener gies (from radio-frequency to far infrared)
From page 120...
... 2012. Circular polarization depen dent cyclotron resonance in large-area graphene in ultrahigh magnetic fields.
From page 121...
... 2010. High-speed terahertz time-domain spectroscopy of cyclotron resonance in pulsed magnetic field.


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