Effect of field dependent core size on reversible magnetization of   high-$\kappa$ superconductors
  The field dependence of the vortex core size $\xi(B)$ is incorporated in the London model, in order to describe reversible magnetization $M(B,T)$ for a number of materials with large Ginzburg-Landau parameter $\kappa$. The dependence $\xi(B)$ is directly related to deviations in $M(\ln B)$ from linear behavior prescribed by the standard London model. A simple method to extract $\xi(B)$ from the magnetization data is proposed. For most materials examined, $\xi(B)$ so obtained decreases with increasing field and is in qualitative agreement both with behavior extracted from $\mu$SR and small angle neutron scattering data and with that predicted theoretically. 
V. G. Kogan, R. Prozorov, S. L. Bud'ko, P. C. Canfield, J. R.   Thompson, J. Karpinski, N. D. Zhigadlo, P. Miranovi\'c