Tuning the static spin stripe phase and supercoductivity in La$_{2-x}$Ba$_{x}$CuO$_{4}$ ($x$ = 1/8) by hydrostatic pressure

Muon spin rotation (${\mu}$SR) and magnetization measurements were performed in stripe-stabilized La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ as a function of pressure up to $p$ ${\simeq}$ 2.25 GPa. At ambient pressure this system exhibits static spin stripe order below $T{\rm so}$ ${\approx}$ 30 K. Zero-field ${\mu}$SR experiments indicate that the volume fraction ${\omega}$ of static spin-stripe order significantly decreases with increasing $p$, while the size of the ordered moment and the ordering temperature remain constant. The magnetization measurements show that the sample exhibits a tiny superconducting (SC) volume fraction at ambient pressure. However, by the application of pressure the SC phase volume increases proportionally to the non-magnetic volume fraction (1-${\omega}$). These results indicate that in La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ magnetism and superconductivity occur in mutually exclusive spatial regions.