Spin-fluctuations in Ti$_{60}$V$_{40}$ alloy and its influence on the   superconductivity
  We report experimental studies of the temperature and magnetic field dependence of resistivity and dc magnetic susceptibility and the temperature dependence of zero field heat capacity in a Ti$_{0.6}$V$_{0.4}$ alloy. The temperature dependence of the normal state dc magnetic susceptibility in this Ti$_{0.6}$V$_{0.4}$ alloy shows T$^2$lnT behavior. The temperature dependence of resistivity follows a T$^2$ behaviour in the range 20-50 K. On the other hand, a term $T^3$ lnT is needed in the expression containing the electronic and lattice heat capacities to explain the temperature dependence of heat capacity at temperatures where $T^2$ dependence of resistivity is observed. Such temperature dependence of dc magnetic susceptibility, resistivity and heat capacity are indications of the presence of spin-fluctuations in the system. Further experimental evidence for the spin fluctuations is obtained in the form of a negative value of T$^5$ term in the temperature dependence of resistivity. The influence of spin-fluctuations on the superconducting properties of Ti$_{0.6}$V$_{0.4}$ is discussed in detail. We show from our analysis of resistivity and the susceptibility in normal and superconducting states that the spin fluctuations present in Ti$_{0.6}$V$_{0.4}$ alloy are itinerant in nature. There is some evidence of the existence of preformed Cooper-pairs in the temperature range well above the superconducting transition temperature. Our study indicates that the interesting correlations between spin-fluctuations and superconductivity may actually be quite widespread amongst the superconducting materials, and not necessarily be confined only to certain classes of exotic compounds. 
Md Matin, L S Sharath Chandra, Radhakishan Meena, M K Chattopadhyay, S   B Roy
cond-mat.supr-con