Eur. Phys. J. B (2014) 87: 131
https://doi.org/10.1140/epjb/e2014-50036-2

Regular Article

The influence of electron-phonon coupling and spin fluctuations on the superconductivity of the Ti-V alloys

¹ Magnetic and Superconducting Materials Section, Raja Ramanna Center for Advanced Technology, Indore, 452 013 Madhya Pradesh, India
² School of Engineering, Indian Institute of Technology Mandi, Kamand, 175005 Himachal Pradesh, India

^a e-mail: lsschandra@rrcat.gov.in

Received: 16 January 2014
Received in final form: 29 April 2014
Published online: 11 June 2014

Abstract

We report a study of the normal and superconducting state properties of the Ti_xV_1−x alloys for x = 0.4, 0.6, 0.7 and 0.8 with the help of dc magnetization, electrical resistivity and heat capacity measurements along with the electronic structure calculation. The superconducting transition temperature T_c of these alloys is higher than that of elemental Ti and is also higher than elemental V for x ≤ 0.7. The roles of electron density of states, electron-phonon coupling and spin fluctuations in the normal and superconducting state properties of these alloys have been investigated in detail. The experimentally observed value of T_c is found to be considerably lower than that estimated on the basis of electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys. There is some evidence as well for the preformed Cooper pair in all these Ti-V alloys in the temperature regime well above T_c. Similar to x = 0.6 [Md. Matin, L.S. Sharath Chandra, R.K. Meena, M.K. Chattopadhyay, A.K. Sinha, M.N. Singh, S.B. Roy, Physica B 436, 20 (2014)], the normal state properties of the x = 0.4 alloy showed the signature of the presence of spin fluctuations. The difference between the experimentally observed T_c and that estimated by considering electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys is attributed to the possible influence of these spin fluctuations. We show that the non-monotonous variation of T_c as a function of x in the Ti_xV_1−x alloys is due to the combined effects of the electron-phonon coupling and the spin fluctuations.