We have studied the magnetic field effects (MFEs) on photo-generated various geminate phenyl-pyrilium/biphenyl radical pair (PP center dot/BP+center dot) of variable singlet/triplet spin-correlations within SDS micelle. When RPs are produced largely with singlet spin-correlation, the MFEs have been observed in two different time domains. It consists of both the initial (t = 0) decrease of radical yield with field, considering nanosecond phenomenon, and comparatively slow microsecond MFE. However, the RPs of relatively lower singlet spin-correlation shows only slow mu s behavior, which may indicate that only singlet spin-state is responsible for exhibiting initial stage MFEs. A kinetic scheme, based on Pedersen's 'super-cage model' for two-stage RP reaction in micelle, has been proposed for analysis. (C) 2009 Elsevier B. V. All rights reserved.