Giant superconducting anisotropy inBi2Sr2

D. E. Farrell

¹

,

S. Bonham

²

,

Jason M. Foster

³

et al.

On the transverse magnetization of the anisotropic superconductor 2H–NbSe2

“…It was already proved by experiments on HTSCs with moderate (Y-Ba-Cu-O) and strong (Ba-Bi-Ca-Cu-O and Tl-superconductors) anisotropy [12,13]. The compound under present study is a classic London superconductor [22], as the magnetic field penetration depth l in it sufficiently exceeds its coherence length x (for the component of M normal to the ab plane, which is responsible for superconductivity, l ab » 1000 Å and the coherence length x c » 10 Å although it is nevertheless larger than the interlayer distance).…”

“…The London model is in reality responsible only for the logarithmic prefactor -M 0 and for the linear dependence of M on ln H in (13). The factor at H c2 under the logarithm appears initially as a fitting parameter.…”

“…Experimental evidence for the existence of transverse magnetization and intrinsic torque of anisotropic HTSC was obtained for the first time in [12]. Later on, intrinsic torque measurements were performed on single crystals of HTSCs [13][14][15] and organic superconductors [14]. In those works the thermodynamic properties of the equilibrium Abrikosov vortex lattice were examined in the framework of London electrodynamics on the basis of an-gle dependence of the torque (Kogan model [11]) and Ginzburg-Landau phenomenology (Clem model [16,17]).…”

Anisotropy of perpendicular field penetration into high-Tc superconductors induced by strong longitudinal field

“…The description of modern magneto-optical techniques can be found elsewhere [6][7][8][9]. Two kinds of the magneto-optical layers for the magnetic flux structure visualization are currently used for investigations: Thin films of europium chalcogenides directly deposited onto the superconductor surface and thus yielding high spatial resolution of 1 ~tm [5,6], and industrially prepared special ferrimagnetic garnet films having a high field sensitivity and providing non-destructive testing of samples [ 7,8 ].…”

“…The latter geometry is often encountered in transport and magnetic measurements in both high-To and traditional superconductors. The additional constant field is a characteristic feature in torque, vibrating-reed and torsionpendulum experiments [9][10][11] because of the necessity to transform the induced magnetic moment into a measured mechanical moment. The effects of the qualitative change of the flux motion in this geometry have been discussed only very recently [ 2 ].…”