Changing the type of superconductivity by magnetic and potential   scattering
  By evaluating the upper and thermodynamic critical fields, $H_{c2}$ and $H_c$, and their ratio $H_{c2}/H_c $ at arbitrary temperatures, we argue that situations are possible when a type-II material is transformed to type-I by adding magnetic impurities. 
V. G. Kogan, R. Prozorov
cond-mat.supr-con