Magnetic Raman scattering in cuprate antiferromagnetic insulators and doped superconductors

Girsh Blumberg; Peter M. Abbamonte; Miles V. Klein

doi:10.1117/12.241756

10 June 1996 Magnetic Raman scattering in cuprate antiferromagnetic insulators and doped superconductors

Girsh Blumberg, Peter M. Abbamonte, Miles V. Klein

Proceedings Volume 2696, Spectroscopic Studies of Superconductors; (1996) https://doi.org/10.1117/12.241756
Event: Photonics West '96, 1996, San Jose, CA, United States

Abstract

We present results of low-temperature two-magnon resonance Raman excitation profile measurements for single layer Sr₂CuO₂Cl₂ and bilayer YBa₂Cu₃O_6.1 antiferromagnets over the excitation region from 1.65 to 3.05 eV. These data reveal composite structure of the two-magnon line shape with peaks at approximately 2.8 and approximately 4 J and strong nonmonotic dependence of the scattering intensity on excitation energy. We analyze these data using the triple resonance theory of Chubukov and Frenkel [Phys. Rev. Lett., 74, 3057 (1995)] and deduce information about magnetic interaction and electronic band parameters in these antiferromagnetic insulators. We study the evolution of the magnetic excitation with hole doping in CuO₂ planes of YBa₂Cu₃O_6+(delta ) and YBa₂Cu₄0₈ single crystals. We find that the spin excitations at energy approximately equal to 3 J, similar to the two-magnon excitations in the insulators, persist with doping and are evidence that antiferromagnetic fluctuations with spatial extent of at least three lattice constants are not overdamped in the underdoped superconductors. The two-magnon resonance study shows the existence of the charge-transfer gap in the underdoped cuprates and provides information about evolution of electronic band parameters with doping. We report a magnetic Raman scattering study of YBa₂Cu₄0₈ superconductor with substitution of Zn on the Cu(2) site. Two and five-tenths percent of substitution softens the two-magnon excitation frequency from 2900 to 2300 cm^-1. This softening is attributed to the absence of a defined spin projection on at least one of eight Cu(2)/Zn sites involved in the superexchange, and it signifies that the Zn- introduced magnetic distortion extends to at lest four Cu sites neighboring a Zn site. The electronic Raman continuum intensity weakens with increasing Zn doping, manifesting a relationship between the Raman continuum and the spin fluctuations.

Citation Download Citation

Girsh Blumberg, Peter M. Abbamonte, and Miles V. Klein "Magnetic Raman scattering in cuprate antiferromagnetic insulators and doped superconductors", Proc. SPIE 2696, Spectroscopic Studies of Superconductors, (10 June 1996); https://doi.org/10.1117/12.241756

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