Universal scaling of the Hall resistivity in MgB2 superconductors
  The mixed-state Hall resistivity and the longitudinal resistivity in superconducting MgB2 thin films have been investigated as a function of the magnetic field over a wide range of current densities from 100 to 10000 A/cm^2. We observe a universal Hall scaling behavior with a constant exponent of 2.0, which is independent of the magnetic field, the temperature, and the current density. This result can be interpreted well within the context of recent theories. 
W. N. Kang, Hyeong-Jin Kim, Eun-Mi Choi, Heon Jung Kim, Kijoon H. P.   Kim, and Sung-Ik Lee