Substitutional Disorder Effect on the Ising-axis Conversion in (Tb_0.5Y_0.5)Cu₂

Abstract

The thermodynamic properties and the results of the Ising-axis conversion of the (Tb_0.5Y_0.5)Cu₂ single crystal are presented. The expected weakening of the magnetic exchange caused by the Y substitution is documented by the lowering of the Néel temperature from T _N =54 K for pure TbCu₂ down to T _N =30 K for (Tb_0.5Y_0.5)Cu₂. Simultaneously, the specific heat data do not show a sharp anomaly at the ordering temperature, the broad transition points to a clustering of Tb and Y ions in the crystal structure. On the other hand, the critical field of the Ising-axis conversion as well as its temperature dependence in (Tb_0.5Y_0.5)Cu₂ is about the same as in pure TbCu₂ which confirms the quadrupolar interaction as the driving force of the conversion process.