skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Magnetic field tunability of spin-polarized excitations in a high-temperature magnet

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1393700
Grant/Contract Number:
FG02-01ER45885
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 9; Related Information: CHORUS Timestamp: 2017-09-21 10:15:42; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Holinsworth, B. S., Sims, H., Cherian, J. G., Mazumdar, D., Harms, N. C., Chapman, B. C. L., Gupta, A., McGill, S. A., and Musfeldt, J. L.. Magnetic field tunability of spin-polarized excitations in a high-temperature magnet. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.96.094427.
Holinsworth, B. S., Sims, H., Cherian, J. G., Mazumdar, D., Harms, N. C., Chapman, B. C. L., Gupta, A., McGill, S. A., & Musfeldt, J. L.. Magnetic field tunability of spin-polarized excitations in a high-temperature magnet. United States. doi:10.1103/PhysRevB.96.094427.
Holinsworth, B. S., Sims, H., Cherian, J. G., Mazumdar, D., Harms, N. C., Chapman, B. C. L., Gupta, A., McGill, S. A., and Musfeldt, J. L.. 2017. "Magnetic field tunability of spin-polarized excitations in a high-temperature magnet". United States. doi:10.1103/PhysRevB.96.094427.
@article{osti_1393700,
title = {Magnetic field tunability of spin-polarized excitations in a high-temperature magnet},
author = {Holinsworth, B. S. and Sims, H. and Cherian, J. G. and Mazumdar, D. and Harms, N. C. and Chapman, B. C. L. and Gupta, A. and McGill, S. A. and Musfeldt, J. L.},
abstractNote = {},
doi = {10.1103/PhysRevB.96.094427},
journal = {Physical Review B},
number = 9,
volume = 96,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on September 21, 2018
Publisher's Accepted Manuscript

Save / Share:
  • We present the designs of probes for making critical current density (J{sub c}) measurements on anisotropic high-temperature superconducting tapes as a function of field, field orientation, temperature and strain in our 40 mm bore, split-pair 15 T horizontal magnet. Emphasis is placed on the design of three components: the vapour-cooled current leads, the variable temperature enclosure, and the springboard-shaped bending beam sample holder. The vapour-cooled brass critical-current leads used superconducting tapes and in operation ran hot with a duty cycle (D) of ∼0.2. This work provides formulae for optimising cryogenic consumption and calculating cryogenic boil-off, associated with current leads usedmore » to make J{sub c} measurements, made by uniformly ramping the current up to a maximum current (I{sub max}) and then reducing the current very quickly to zero. They include consideration of the effects of duty cycle, static helium boil-off from the magnet and Dewar (b{sup ′}), and the maximum safe temperature for the critical-current leads (T{sub max}). Our optimized critical-current leads have a boil-off that is about 30% less than leads optimized for magnet operation at the same maximum current. Numerical calculations show that the optimum cross-sectional area (A) for each current lead can be parameterized by LI{sub max}/A=[1.46D{sup −0.18}L{sup 0.4}(T{sub max}−300){sup 0.25D{sup −{sup 0{sup .{sup 0{sup 9}}}}}}+750(b{sup ′}/I{sub max})D{sup 10{sup −{sup 3I{sub m}{sub a}{sub x}−2.87b{sup ′}}}}]× 10{sup 6}A m{sup −1} where L is the current lead's length and the current lead is operated in liquid helium. An optimum A of 132 mm{sup 2} is obtained when I{sub max} = 1000 A, T{sub max} = 400 K, D = 0.2, b{sup ′} = 0.3 l h{sup −1} and L = 1.0 m. The optimized helium consumption was found to be 0.7 l h{sup −1}. When the static boil-off is small, optimized leads have a boil-off that can be roughly parameterized by: b/I{sub max } ≈ (1.35 × 10{sup −3})D{sup 0.41} l h{sup ‑1} A{sup −1}. A split-current-lead design is employed to minimize the rotation of the probes during the high current measurements in our high-field horizontal magnet. The variable-temperature system is based on the use of an inverted insulating cup that operates above 4.2 K in liquid helium and above 77.4 K in liquid nitrogen, with a stability of ±80 mK to ±150 mK. Uniaxial strains of −1.4% to 1.0% can be applied to the sample, with a total uncertainty of better than ±0.02%, using a modified bending beam apparatus which includes a copper beryllium springboard-shaped sample holder.« less
  • Application of polarization proton scatterings to radioactive nuclear beam experiments is proposed. A polarized proton solid target which works at a high temperature of several tens of Kelvin and in a low magnetic field of {approx} 0.1 T is needed for the purpose. The proton polarization can be produced by transferring an electron population difference in photo-excited triplet states of an aromatic molecule by means of a cross polarization technique. By using this method, we have constructed a polarized proton solid target specifically designed for use in radioactive nuclear beam experiments. The target has been used in the measurement ofmore » vector analyzing power for the p - 6He elastic scattering at 71 MeV/A.« less
  • High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La{sub 1.895}Sr{sub 0.105}CuO{sub 4} (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer Q{sub IC}=(0.5,0.5{+-}{delta},0),(0.5{+-}{delta},0.5,0) exhibits an anomaly at the superconducting T{sub c} which broadens and shifts to lower temperature upon the application of a magnetic field along the c axis. A field-induced enhancement of the spectral weight is observed, but only at finite energy transfers and in an intermediate temperature range. These observations establish the opening of a strongly downward renormalized spin gap in the underdoped regime ofmore » LSCO. This behavior contrasts with the observed doping dependence of most electronic energy features.« less
  • We discuss the spin excitations of a simple model of an ultrathin ferromagnetic film, in which the magnetic moment bearing electrons are itinerant in character. The one-band Hubbard model, treated in mean-field theory, forms the basis of the discussion. The spin excitations are treated by means of the random-phase approximation. We find spin-wave modes of standing wave character, and a spectrum of Stoner excitations influenced strongly by size effects. While the dispersion relations of the standing spin-wave modes appear as expected from a localized-spin model, there are substantive differences between the itinerant- and localized-spin cases. An example is the numbermore » of spin-wave modes evident in the appropriate spectral density functions, for each wave vector. We use a previously developed formalism of spin-polarized electron-energy-loss scattering (SPEELS) to compute SPEELS spectra for our model film. In addition to a broad feature with origin in Stoner excitations, we find clear and relatively intense spin-wave loss peaks.« less