Muon spin relaxation study of the stripe phase order in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">La</mml:mi></mml:mrow><mml:mrow><mml:mn>1.6</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Nd</mml:mi></mml:mrow><mml:mrow><mml:mn>0.4</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CuO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and related 214 cuprates

We present zero-field muon spin relaxation (\ensuremath{\mu}SR) measurements of ${\mathrm{La}}_{1.6\ensuremath{-}x}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ with $x=0.125,0.15,0.2;{\mathrm{La}}_{1.475}{\mathrm{Nd}}_{0.4}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4},{\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4},$ and ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125\ensuremath{-}y}{\mathrm{Sr}}_{y}{\mathrm{CuO}}_{4}$ 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 ${T}_{N}\ensuremath{\approx}30\mathrm{K},$ with a $\stackrel{\ensuremath{\rightarrow}}{T}0$ ordered Cu moment $\ensuremath{\approx}0.3{\ensuremath{\mu}}_{B}.$ 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 \ensuremath{\mu}SR hysteresis measurements of the ${\mathrm{La}}_{1.45}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_{4}$ and ${\mathrm{La}}_{1.4}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{0.2}{\mathrm{CuO}}_{4}$ 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.