The magnetic composite BiOCl-SrFe12O19, a novel p-n type heterojunction was synthesized
by hydrolysis with a medium temperature sintering method. The microstructure and magnetic
properties of the prepared material were characterized by FTIR, XRD, SEM, TEM, HRTEM,
SAED, and VSM. The results showed the  facet of BiOCl with high photocatalytic
activity was exposed in the BiOCl-SrFe12O19. The heterostructured BiOCl-SrFe12O19
had better magnetic properties, contributing to its reuse and improvement in photocatalysis.
Moreover, the composite was blessed with excellent photocatalytic activity and stability.
In the BiOCl-SrFe12O19 system, SrFe12O19 not only inhibited the growth of BiOCl along
the  direction to enhance the exposure of the  wafer, but also acted as
a sensitizer absorbing light irradiation. The magnetic field generated from SrFe12O19
made BiOCl, under light irradiation, produce more photo-induced electrons and holes
and simultaneously hampered their recombination. For the first time we propose the
possible mechanism of how to enhance photocatalytic activity by a magnetic field effect
originating from the magnetic photocatalyst itself.