Critical Field Anisotropy in an Organic Superconductor β-(BEDT–TTF)₂IBr₂

抄録

A measurement of the anisotropy of the upper critical field H_c2 in an organic superconductor β-(BEDT–TTF)₂IBr₂ is reported. A large anisotropy is observed with high critical fields when the magnetic field is applied in the crystallographic a-b plane and a low critical field in the perpendicular direction (H_c2^a : H_c2^b′ : H_c2^c*\simeq25 : 24 : 1). The increased superconducting transition temperature (T_c=2.2–2.3 K with the onset at 2.8 K), compared with the isostructural β-(BEDT–TTF)₂I₃, is attributed to the decreased lattice parameters.