Fermi Liquid Effect on Tricritical Superconducting Transitions in Thin TiN Films under the Spin Paramagnetic Limitation

Reentrant first order and second order transitions are observed in thin TiN films under the paramagnetic limitation of superconductivity, where the temperature gradients of critical fields are positive. Then, the superconducting condensate has to have higher entropy than the normal state immediately below the critical fields. The observations of reentrant transition in thin TiN films above the tricritical point reveal that the renormalized Fermi liquid effect plays an important role for the superconducting transition. The antisymmetric Fermi liquid parameters obtained from the temperature dependence of critical field have positive definite values of 0.23. Spin orbit scattering parameters almost inversely increase with decreasing film thickness. Orbital depairing parameters are almost linear to the square of film thickness.