Magnetoresistivity and H_c2(T) in MgB₂

Detailed magnetotransport data on dense wires of MgB₂ are reported for applied magnetic fields up to 18 T. The temperature and field dependencies of the electrical resistivity are consistent with MgB₂ behaving like a simple metal and following a generalized form of Kohler’s rule. In addition, given the generally higher-T_c values and narrower resistive transition widths associated with MgB₂ synthesized in this manner, combined with applied magnetic fields of up to 18 T, an accurate and complete H_c2(T) curve could be determined. This curve agrees well with curves determined from lower field measurements on sintered pellets and wires of MgB₂. H_c2(T) is linear in T over a wide range of temperature (7K<~T<~32K) and has an upward curvature for T close to T_c. These features are similar to other high κ, clean limit, boron-bearing intermetallics: YNi₂B₂C and LuNi₂B₂C.