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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

From One- to Two-Magnon Excitations in the S = 3 / 2 Magnet β - CaCr 2 O 4

Here, we apply neutron spectroscopy to measure the magnetic dynamics in the S = 3 / 2 magnet β-CaCr 2 O 4 ( T N = 21 K ). The low-energy fluctuations, in the ordered state, resemble large- S linear spin waves from the incommensurate ground state. However, at higher energy transfers, these semiclassical and harmonic dynamics are replaced by an energy and momentum broadened continuum of excitations. Applying kinematic constraints required for energy and momentum conservation, sum rules of neutron scattering, and comparison against exact diagonalization calculations, we show that the dynamics at high-energy transfers resemble low- S one-dimensional quantum fluctuations. β-CaCr 2 O 4 represents an example of a magnet at the border between classical Néel and quantum phases, displaying dual characteristics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Magnetosynthesis effect on magnetic order, phonons, and magnons in single-crystal Sr 2 ⁢ IrO 4

It was shown earlier that applying a magnetic field during the growth of Sr 2 IrO 4 , also known as “field-alteration”, induces significant changes to its structural, magnetic, and transport properties. However, the microscopic nature of these changes is enigmatic. Here, in this study, we employed resonant elastic and inelastic x-ray scattering, as well as Raman scattering, to investigate samples from two batches of Sr 2 IrO 4 grown in magnetic fields of different strengths. Our findings reveal that samples grown in a weaker magnetic field have similar magnetic order to non-altered samples, whereas those grown in a stronger field show a different stacking of weak in-plane ferromagnetic moments. Additionally, we observed significant softening and broadening of select Raman-active phonons in the field altered samples, with a stronger effect in the samples grown in the stronger field. We discuss insights that our results provide into the microscopic nature of field-alteration in Sr 2 IrO 4 .

36 MATERIALS SCIENCE↗