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Antiferromagnetic resonance in La 2 CuO 4 + y</mml:mi…

1989; American Physical Society; Volume: 40; Issue: 7 Linguagem: Inglês

10.1103/physrevb.40.5190

1095-3795

S. G. Kaplan, T. W. Noh, A. J. Sievers, S-W. Cheong, Z. Fisk,

Magnetic and transport properties of perovskites and related materials

Our attempts to observe the antiferromagnetic resonance (AFMR) modes in ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4+\mathrm{y}}$ in both single crystal and small particle forms have been unsuccessful. An argument based on a magnetic-susceptibility sum rule shows that the resonance previously identified with the AFMR in polycrystalline ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4+\mathrm{y}}$ [R. T. Collins, et 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 ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4+\mathrm{y}}$ transmission measurements versus magnetic field. Additional measurements on small particles show that the broad resonant feature observed around 8 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ is produced by an electric-dipole-active superconducting sphere resonance of the ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4+\mathrm{y}}$ particles.