2005/07/01 by C. Y. Yang, B. C. Chang, H. C. Ku +1
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.72.174508
7 figures
arxiv created 2005/07/01 · openalex publication_date 2005/11/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
A spontaneous vortex state (SVS) between 30 and 56 K was observed for the weak-ferromagnetic superconductor RuSr2GdCu2O8 with the ferromagnetic Curie temperature TC=131\phantom\rule0.3em0exK and the superconducting transition temperature Tc=56\phantom\rule0.3em0exK. The low-field (\ifmmode±\else\textpm\fi20\phantom\rule0.3em0exG) super-conducting hysteresis loop indicates a narrow Meissner state region within the average lower critical field Bc1(T)=Bc1(0)[1\ensuremath-(T∕T0)2], with average Bc1ave(0)=12\phantom\rule0.3em0exG and T0=30\phantom\rule0.3em0exK. Full Meissner shielding signal in very low applied field indicates an ab plane Bc1ab(0)\ensuremath∼4\phantom\rule0.3em0exG with an estimated anisotropic parameter \ensuremathγ\ensuremath∼7 for this layered system. The existence of a spontaneous vortex state between 30 and 56 K is the result of weak-ferromagnetic order with a net spontaneous magnetic moment of \ensuremath∼0.1\ensuremathμB∕Ru, which generates a weak magnetic dipole field around 10 G in the CuO2 bilayers. The upper critical field Bc2 varies linearly as (1\ensuremath-T∕Tc) up to 7-T field. The vortex melting line Bm varies as (1\ensuremath-T∕Tm)3.5 with melting transition temperature Tm=39\phantom\rule0.3em0exK and a very broad vortex liquid region due to the coexistence and the interplay between superconductivity and weak-ferromagnetic order.