An improvement of ferrite substrate

The surfaces of hot isostatically pressed (HIP) high density ferrite substrates were lapped, polished and finished ultra-fine by various methods. The quality of these finished surfaces was evaluated by a stylus instrument, electron diffraction and ellipsometry. In this paper, the correlation between the surface roughness and the thickness of the surface dead layer is discussed. The results showed that the ellipsometry is the recommended technique to measure the dead layer nondestructively.