Reversible effect of hydrogen on superconductivity and weak ferromagnetism inEu1.4Ce0.6MSr2Cu2O10−δ(M=Nband Ru)

Abstract

We have investigated the superconducting compounds ${\mathrm{Eu}}_{1.4}{\mathrm{Ce}}_{0.6}M{\mathrm{Sr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ ($M=\mathrm{Nb}$ and Ru) (${T}_{c}=22$ and 32 K, respectively), as well as these materials charged with hydrogen, by several complementary experimental techniques. ${\mathrm{Eu}}_{1.4}{\mathrm{Ce}}_{0.6}{\mathrm{RuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ is magnetically ordered at ${T}_{N}=122\mathrm{K},$ thus ${T}_{N}\ensuremath{\gg}{T}_{c}.$ Superconductivity (SC) is confined to the ${\mathrm{CuO}}_{2}$ planes, and the magnetic ordering is due to the Ru sublattice. Among many interesting features, irreversibility phenomena at low magnetic fields and a magnetic spin reorientation transition, which are observed, originate from antisymmetric exchange coupling of the Dzyaloshinsky-Moria type. The effect of hydrogen (0.35 at. %) is to suppress SC in both compounds and to enhance the weak-ferromagnetic properties of the Ru sublattice ${(T}_{N}=225\mathrm{K}).$ In contrast to other high-${T}_{c}$ materials, this effect is reversible: namely, by depletion of hydrogen, SC is restored in both materials and for $M=\mathrm{Ru},$ the ${T}_{N}$ drops back to 122 K.