Evolution of ferromagnetism in Ru doped UCoGe studied by PND and XMCD

Pospisil, J.; Haga, Yoshinori   ; Yamamoto, Etsuji  ; Takeda, Yukiharu   ; Okane, Tetsuo  ; Yamagami, Hiroshi*; Valika, M.*; Stunault, A.*; Gillon, B.*; Prokes, K.*; Nenert, G.*; Chapon, L.*; Gukassov, A.*; Cousson, A.*; Sechovsk, V.*

We present that Ru substitution on the Co site in UCoGe leads to an initial sharp increase of the Curie temperature TC up to the maximum of 8.5 K for 12 of dopant. Further increase of the Ru content leads to the suppression of both the TC and spontaneous magnetic moment. Hand in hand with ferromagnetism increase suppression of superconductivity appears. Concentration dependence of the critical exponents of resistivity and heat capacity together with scaling of the TC has signs of the non-Fermi liquid (nFL) behavior around 30 of Ru. Latter performed PND and XMCD experiments assign ferromagnetism enhancement to growth of uranium orbital moment and mainly to dramatic transformation in Co sublattice. In contrast to parent UCoGe, we found parallel orientation of the U and Co moments in UCoRuGe and UCoRuGe single crystals.