μSR study of magnetic order in La2-xMxCu1-yZnyO4 (M = Sr, Ba)

Zero-field muSR measurements have been performed on Zn-free and Zn-substituted samples of La2-xSrxCuO4 (LSCO) and La2-xBaxCuO4 (LBCO) over a wide doping range. In LSCO and LBCO, around x similar to 1/8, superconductivity is suppressed in the same doping range where magnetic order appears, suggesting that superconductivity competes with the magnetic order. Zn substitution induces or enhances the magnetic order for LSCO, but depresses the magnetic order for LBCO. The difference is attributed to the existence of stable static magnetic correlations in LBCO. In the doping range around x similar to 1/8 the magnetic ordering temperature is almost independent of the doping, which indicates segregation of the spin and hole regions. The constant internal magnetic field observed around x similar to 1/8 is much smaller than that for La2CuO4, suggesting that the magnetic order around x similar to 1/8 is essentially different from the three-dimensional antiferromagnetic order in La2CuO4. The estimated magnetic volume fraction reaches 100% even in the superconducting region. (C) 2002 Elsevier Science B.V. All rights reserved.