and when the amount of presence of the silicon component exposed on the surface, expressed in terms of silicon, with {HEAD ~ respect} to {TAIL ~ the magnetite particles} is designated as B, the relationship C/B≧15 is satisfied 
to
and when the amount of presence of the silicon component exposed on the surface , expressed in terms of silicon , with { HEAD ~ respect } to { TAIL ~ the magnetite particles } is designated as B , the relationship C / B≧15 is satisfied
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH