Showing papers by "Tae Won Noh published in 1989"
TL;DR: A far-infrared sphere resonance has been observed in superconducting La/sub 2-// sub x/Sr/sub x/CuO/sub 4-//sub y/ isolated small particles at low temperatures.
Abstract: A far-infrared sphere resonance has been observed in superconducting La/sub 2-//sub x/Sr/sub x/CuO/sub 4-//sub y/ isolated small particles at low temperatures. The frequency and strength of this electronic mode increase with increased Sr doping, decrease with applied magnetic field, and decrease as the temperature is raised; the resonance disappears above the superconducting transition temperature. This superconducting sphere resonance occurs at a frequency below the energy gap and is polarized along the c axis of the particle.
10 citations
TL;DR: In this paper, Collins et al. showed that the resonance previously identified with the antiferromagnetic resonance (AFMR) in polycrystalline La{sub 2}CuO{sub 4+{ital y}} (R. T. Collins, {ital et} {ital al}., Phys. Rev. B 37, 5817 (1988)) is too strong to be compatible with a magnetic spinwave mode.
Abstract: Our attempts to observe the antiferromagnetic resonance (AFMR) modes in La{sub 2}CuO{sub 4+{ital y}} in both single crystal and small particle forms have been unsuccessful. An argument based on a magnetic-susceptibility sum rule shows that the resonance previously identified with the AFMR in polycrystalline La{sub 2}CuO{sub 4+{ital y}} (R. T. Collins, {ital et} {ital al}., Phys. Rev. B 37, 5817 (1988)) is too strong to be compatible with a magnetic spin-wave mode. No evidence of an AFMR mode is found in our single-crystal La{sub 2}CuO{sub 4+{ital y}} transmission measurements versus magnetic field. Additional measurements on small particles show that the broad resonant feature observed around 8 cm{sup {minus}1} is produced by an electric-dipole-active superconducting sphere resonance of the La{sub 2}CuO{sub 4+{ital y}} particles.
5 citations