Polarized neutron diffraction and X-ray magnetic circular dichroism study of Ru doped UCoGe

TL;DR

This study investigates how Ru doping enhances ferromagnetism in UCoGe by using polarized neutron diffraction and X-ray magnetic circular dichroism, revealing increased Curie temperatures and orbital uranium moments.

Contribution

It provides new microscopic insights into ferromagnetism enhancement in Ru-doped UCoGe, highlighting the role of orbital uranium moments and 5f-ligand hybridization.

Findings

Curie temperature increases with Ru doping

Orbital uranium moments grow with doping

Parallel orientation of U and Co moments in doped samples

Abstract

We report on microscopic study of the ferromagnetism enhancement in the Ru doped ferromagnetic superconductor (FM SC) UCoGe. For that purpose, two single crystals with composition UCo0.97Ru0.03Ge and UCo0.88Ru0.12Ge were prepared. Both single crystals were investigated by polarized neutron diffraction (PND) at low temperatures in magnetic fields and the latter one also by the soft X-ray magnetic circular dichroism (XMCD) method. UCo0.96Ru0.03Ge and UCo0.88Ru0.12Ge have been found ordering ferromagnetically below the Curie temperature TC = 6 K and 8.5 K, respectively, which are considerable higher than TC = 3 K of UCoGe. The increase of TC is accompanied by enhancement of the spontaneous moment to ms = 0.11 mB/f.u. and ms = 0.21 mB/f.u., respectively. The analysis of the PND results assigns the ferromagnetism enhancement mainly to the growth of the orbital part of uranium 5 f moment. In contrast to the published results of PND study of the parent UCoGe, we have found parallel orientation of the U and Co moments in both doped compounds. Evolution of magnetic characteristics with Ru concentration is discussed within a scenario considering the varying 5 f-ligand hybridization as the key mechanism.