Study of upper critical field in superconducting borocarbides RNi2B2C (R Y, Ho, Er, Tm)

Abstract We have determined upper critical field, H c2 ( T ), from resistivity measurements in the borocarbide superconductors, RNi 2 B 2 C (R  Y, Ho, Er, Tm). The H c2 ( T ) of thesematerials show a positive curvature which is unlike of a conventional type-II superconductor. Features corresponding to coexistence of superconductivity and magnetism are observed in HoNi 2 B 2 C and ErNi 2 B 2 C. From the resistivity measurements, we observe a double reentrant behaviour in our sample of HoNi 2 B 2 C.