Heat capacity of the heavy fermion superconductor CeIrIn5 under hydrostatic pressure

CeIrIn5 belongs to a new class of heavy fermion (HE) superconductors that crystallize in the tetragonal HoCoGa5-structure. This structure can be regarded as alternating layers of CeIn3 and IrIn2. Bulk CeIn(3)undergoes a transition from an antiferrornagnetic (AFM) state at ambient pressure (T-N = 10 K) to a superconductina state (T-c = 0.15 K) at a critical pressure p(c) = 2.8 GPa at which long range magnetic order vanishes. It is. therefore, regarded as a possible candidate for magnetically mediated superconductivity (SC). We report on measurements of the heat capacity of CeIrIn5 at hydrostatic pressure pless than or equal to1.6 GPa. With increasing pressure, T-c increases almost linearly up to the maximum pressure applied, while the effective mass of the quasiparticles m(eff) decreases as indicated by the ratio C/T (T = 1 K). This may be interpreted as the stabilization of the superconducting state by the increase of the characteristic spinfluctuation temperature T-SF (T-SF:infinityk(p)(2)/c m(eff)). (C) 2002 Elsevier Science B.V. All rights reserved.