Muon spin relaxation study of the stripe phase order in La1.6-xNd0.4SrxCuO4 and related 214 cuprates

We present zero-field muon spin relaxation (μSR) measurements of La1.6-xNd0.4SrxCuO4 with x=0.125,0.15,0.2; La1.475Nd0.4Ba0.125CuO4, La1.875Ba0.125CuO4, and La1.875Ba0.125-ySryCuO4 with y=0.025,0.065. All of the samples with dopant concentrations x+y<~0.15 show similar static magnetic order with coherent precession of the muon spins below TN≈30 K, with a T→0 ordered Cu moment ≈0.3μB. The samples with x=0.20 show no coherent precession but manifest two distinct relaxation regimes, typical of quasistatic magnetism. We then present transverse-field μSR hysteresis measurements of the La1.45Nd0.4Sr0.15CuO4 and La1.4Nd0.4Sr0.2CuO4 systems that show a large superconducting response below approximately 7 K and 12 K, respectively. We argue that superconductivity and magnetic order coexist in the x=0.15 system.