Crossover of superconductivity across the antiferromagnetic end point in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>FeSe</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:m

Temperature-pressure ($T\ensuremath{-}P$) phase diagrams of ${\mathrm{FeSe}}_{1\ensuremath{-}\mathrm{x}}{\mathrm{S}}_{\mathrm{x}}$ were investigated by the measurements of dc magnetization ($M$) and electrical resistivity ($\ensuremath{\rho}$) under pressure, using single crystal specimens with $x$ = 0.04, 0.08, and 0.13. For all specimens, the $M(T$) curves under pressure near the end point of the antiferromagnetic (AFM) phase are found to show a two-step diamagnetic response, which can be described as the sum of two diamagnetic components ${M}_{1}(T$) and ${M}_{2}(T$), indicating that two superconducting (SC) phases with different ${T}_{\mathrm{c}}$ values coexist within a pressure range of $\mathrm{\ensuremath{\Delta}}P\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. Moreover, the pressure dependence of the amplitudes of ${M}_{1}(T$) and ${M}_{2}(T$) indicates a continuous transfer of the volume fraction between the two SC phases. These behaviors suggest that a crossover of superconductivity occurs in conjunction with the emergence of AFM phase and imply that the SC phases inside and outside the AFM phase could have different origins.