Thermal conductivity study of Sr₂RuO₄ in oriented magnetic field

Thermal conductivity κ was measured on high quality single crystals of Sr₂RuO₄, with T_c = 1.37 K close to the value for impurity free material (1.5 K). Linear decrease of κ/T in T is found below 1 K. Dependence of κ/T on magnetic field perpendicular to the conducting plane is consistent with the behavior of type II superconductor, giving H_C1≈0.01 T and H_C2=0.08 T. In parallel magnetic field κ/T vs. H dependence is principally different, showing rapid restoration of conductivity in narrow vicinity of the upper critical field. This behavior is in good agreement with a T-H phase diagram determined from the specific heat and AC susceptibility measurements and is assigned to the field-induced formation of a superconducting state with nodes in the gap.