151Eu Mössbauer and magnetic studies on magnetic superconductor [formula omitted

Abstract

Magnetic and 151Eu Mössbauer studies have been carried out on the ruthenocuprate magnetic superconductors, EuSr 2 Ru 1 - x Cu 2 + x O 8 ( - 0.1 ⩽ x ⩽ 0.25 ) . The magnetic ordering temperature ( T M ) 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 T M . The 151Eu Mössbauer studies show that the Eu ions are in 3+ ( 4 f 6 , 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.