A cage 1, wherein an oxide layer comprising {HEAD ~ an Fe3O4 phase} as {TAIL ~ a main ingredient} and not containing or Fe2O3 phase is present at a thickness of 50 nm or more further on the surface of the nitride layer 
A cage 1 , wherein an oxide layer comprising { HEAD ~ an Fe3O4 phase } as { TAIL ~ a main ingredient } and not containing or Fe2O3 phase is present at a thickness of 50 nm or more further on the surface of the nitride layer
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH