Magnetic pair breaking and weak ferromagnetism in single crystals ofEr1−xTbx

Abstract

The magnetic and superconducting properties in the single crystals of Er 1Ϫx Tb x Ni 2 B 2 C compounds are investigated by temperature-dependent magnetization M (T) and in-plane resistivity (T). It is found that the superconducting transition temperature is suppressed by adding Tb in the sites of Er and it follows well de Gennes scaling for both T c ϾT N and T c ϽT N . From the T c variation, the magnetic pair breaking strength of Tb is estimated to be similar to the Er. The antiferromagnetic and weak ferromagnetic transition temperatures show distinct behaviors in terms of the de Gennes factor in the Er-rich (xр0.4) and Tb-rich (xу0.6) side. These observations will be discussed under the consideration of magnetic ground states of ErNi 2 B 2 C and TbNi 2 B 2 C and their interactions.

Superconductivity of MgB2in the BCS framework with emphasis on extrinsic effects on critical temperature

“…The substitution of Mn and Fe in the MgB 2 system is particularly interesting due to the magnetic properties of these materials. Substitutions with magnetic impurities are expected to suppress superconductivity dramatically because of the spinflip pair breaking scattering (due to the exchange interaction between conduction electrons and magnetic moments of the substituted ions) [233][234][235][236][237][238][239][240]. For Fe doping the T C decreases with increasing Fe [241][242][243][244].…”