Rare-earth-ion-size control on magnetic irreversibility field in CuBa 2RECu 2O 7− δ

Abstract

For CuBa 2RECu 2O 7− δ (Cu-1212:P), the dependence of magnetic irreversibility field ( H irr) on the ionic radius of rare earth element (RE) has been studied. CuBa 2RECu 2O 7− δ samples with the RE ionic radii [ r(RE)] varying from 0.982 Å (for RE=Yb 0.6Lu 0.4) to 1.079 Å (for RE=Sm) were studied. The oxygen content of all the samples was set at a fixed level, i.e. δ=0.06±0.03. With decreasing r(RE), the H irr characteristics, i.e. the H irr vs (1− T/ T c) plot, was clearly enhanced. The CuBa 2(Yb 0.6Lu 0.4)Cu 2O 6.92 sample showed a record-high H irr value of ∼9.0 T at 77 K. This result implies that through isovalent cation substitution the carrier-density distribution may be optimized to facilitate the superior H irr property.