Observation of the vortex lattice phase transition in the specific heat inLa1.86Sr0.14CuO4 single crystal

Specific heat and magnetization have been measured on La1.86Sr0.14CuO4 sing le crystal in order to investigate the vortex lattice phase transition in t he mixed state under magnetic field up to 120 kOe. Clear anomaly and jump c ome from the phase transition of the vortex lattice were observed in the sp ecific heat and the magnetization, respectively. The temperatures of the vo rtex lattice phase transition and the entropy change accompanied with it we re consistent between both measurements. The temperature dependence of the phase transition obeys the relation of H-m = H-m0(1 - T/T-c)(1.7) by meltin g of the vortex lattice in the magnetic field below 50 kOe and H-d = H-d0(T -c/T - 1) by sublimation of the vortex lattice in the higher field. The res ults strongly suggest a possibility of a crossover from the vortex lattice melting to the sublimation at about 50 kOe. (C) 2002 Elsevier Science B.V. All rights reserved.