151Eu Mössbauer and magnetic studies on magnetic superconductor EuSr2 Ru1 - x Cu2 + x O8 ( - 0.1 ≤ x ≤ 0.25 )

Abstract

Magnetic and 151Eu Mössbauer 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 135 K for x=0.0 to 125 K for x=0.25 and the superconducting transition temperature increases from 19 K (onset for x=0.0) to 33 K (x=0.1). The compounds with x<0 do not show superconductivity down to 2 K but show an increase in TM. The 151Eu Mössbauer 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 Mössbauer absorption spectra below the magnetic ordering temperature indicates a small transferred magnetic hyperfine field at the Eu site.