We analyze the data for the pressure and boron isotope effect on the temperature dependence of the magnetization near Tc. Invoking the universal scaling relation for the magnetization at fixed magnetic field it is shown that the relative shift of Tc, induced by pressure or boron isotope exchange, mirrors essentially that of the anisotropy. This uncovers a novel generic property of anisotropic type II superconductors, inexistent in the isotropic case. For MgB2 it implies that the renormalization of the Fermi surface topology due to pressure or isotope exchange is dominated by a mechanism controlling the anisotropy.
@article{arxiv.cond-mat/0502202,
title = {Pressure and isotope effect on the anisotropy of MgB$_{2}$},
author = {T. Schneider and D. Di Castro},
journal= {arXiv preprint arXiv:cond-mat/0502202},
year = {2009}
}