Magnetic order in La1.9Sr0.1CuO4 from two-magnon Raman scattering

Abstract

In a single crystal of La1.9Sr0.1CuO4 which has a suppressed T-c of 12 K, we observed strong, temperature-dependent two-magnon Raman scattering which indicates an ordered spin phase in the CuO2 plane below T = 40 K. We analyzed the line shape of the two-magnon scattering within the traditional Loudon-Fleury theory and found a superexchange constant J = 1519 K. The calculation of the frequency moments of the spectra suggests that quantum fluctuations are very weak in the ground state. The magnetic scattering in La1.9Sr0.1CuO4 is totally different from that reported in the parent compound La2CuO4.