Effect of hole doping and antiferromagnetic coupling on the itinerant ferromagnetism of through Cu substitution at Ru site

Systematic studies on the structural, transport and magnetic properties of SrRu1−xCuxO3  ( x = 0.0 – 0.2 ) compounds have been performed. SrRu0.8Cu0.2O3 shows a tetragonal structure unlike the other compositions which exhibit a pseudo-cubic structure. Low temperature powder X-ray diffraction data of SrRu0.8Cu0.2O3 collected at a synchrotron beam line reveals that the tetragonal structure is stable down to 8 K. Ferromagnetic transition temperatures ( T c ) are significantly reduced from 160 to 34 K with Cu doping. All the compositions exhibit irreversibilities in MZFC(T) and MFC(T) curves ascribable to the presence of domain structures. Magnetic susceptibility measurements show that the copper ions are anti-ferromagnetically coupled for concentrations higher than x = 0.16 . The antiparallel arrangement of Ru5+ ions with its neighboring cations also contributes to the large reduction in the observed magnetic moment. X-ray photoemission spectroscopy measurements show evidence for both tetravalent and pentavalent Ru ions while copper is in a divalent state. We conclude from our resistivity data that Cu2+ substitution promotes a polaronic type of conductivity.