Low temperature specific heat of polycrystalline UGe 2 at high pressure

•Ralf Vollmer1, Christian Pfleiderer1, Hilbert v. Löhneysen1,2, Eric D. Bauer3 und M. Brian Maple3
2Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe, Germany
3Institute for Pure and Applied Physical Sciences and Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
1Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe

In UGe 2 , superconductivity in coexistence with ferromagnetism is observed in single crystal [1] and polycrystalline samples [2] the pressure pc » 16  kbar for which the Curie temperature TC drops to zero. We present measurements of the specific heat C in the range 0.1 K to 2.5 K on polycrystalline samples up to 14.7 kbar. The linear coefficient of the specific heat, g = C/T , increases as a function of pressure and is the highest in the p -range where superconductivity is observed. In the superconducting state the a.c. magnetic susceptibility exhibits strong diamagnetic shielding. The specific heat displays an anomaly that is indicative of a bulk superconducting transition of order 15 to 20% by volume. The observed properties reflect an intricate interplay of the coexistence of ferromagnetism and superconductivity in UGe 2 .

[1] S. Saxena et al., Nature 406 (2000) 587; A. Huxley et al., Phys. Rev. B 63 (2001) 144519.

[2] E. D. Bauer et al., J. Phys.: Cond. Matt. 13 (2001) L759.