Critical current density anisotropy of aligned MgB2 crystallites

We have obtained the induced critical current density, J(c) proportional to DeltaM, with DeltaM taken from hysteretic magnetization loops measured for temperatures between 5 and 35 K, in a sample of aligned MgB2 crystallites. We found an almost temperature independent ratio J(c)(ab)/J(c)(c) similar to 1.5, between the critical current density parallel and perpendicular to the ab planes. This latter result follows closely the expected dependence of J(c)(ab)/J(c)(c) approximate to xi(ab)/xi(c) similar to 1.7, where xi(ab) and xi(c) are the corresponding coherence length values. Uncertainties related to the evaluation of geometric factors and subtraction of a magnetic background are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.