151Eu Mossbauer and magnetic studies on magnetic superconductor EuSr2Ru1-xCu2+xO8(-0.1=<x=<0.25)

Magnetic and 151Eu Mossbauer studies have been carried out on the ruthenocuprate magnetic superconductors, EuSr2Ru1-xCu2+xO8(-0.1=<x=<0.25). The magnetic ordering temperature (TM) decreases from 135K for x=0.0 to 125K for x=0.25 and the superconducting transition temperature increases from 19K (onset for x=0.0) to 33K (x=0.1). The compounds with x<0 do not show superconductivity down to 2K but show an increase in TM. The 151Eu Mossbauer studies show that the Eu ions are in 3+ (4f6,J=0) and hence in the nonmagnetic state in these compounds. The observation of a broadening in the 151Eu Mossbauer absorption spectra below the magnetic ordering temperature indicates a small transferred magnetic hyperfine field at the Eu site