Varying Eu2+magnetic order by chemical pressure in EuFe2(As1−xPx)2

Based on low-field magnetization measurements on a series of single crystals, we present a scheme of the Eu${}^{2+}$ spin alignment in EuFe${}_{2}$(As${}_{1\ensuremath{-}x}$P${}_{x}$)${}_{2}$. We explain observations of the Eu${}^{2+}$ ordering previously reported, reconciling different existing phase diagrams. The magnetic moments of the Eu${}^{2+}$ ions are slightly canted, yielding a ferromagnetic contribution along the $c$ direction that becomes stronger with pressure, until superconductivity sets in. The spin-density wave as well as the superconducting phase coexist with an antiferromagnetic interlayer coupling of the canted spins. Reducing the interlayer distance finally leads to a ferromagnetic Eu${}^{2+}$ interlayer coupling and to the suppression of superconductivity.