Structural and soft magnetic properties of nitrogen added iron film prepared by sputter-deposition.

Abstract

The effect of the addition of nitrogen gas on the structural and soft magnetic properties of rf sputter-deposited iron films has been investigated. An iron film containing nitrogen with such good soft magnetic properties as a large saturation magnetic flux density B_s of about 2 OkG and a small coercive force H_c of about 1.0 Oe was obtained in Ar gas of 3.0×10^-3 Torr containing N₂ gas of between 2.5×10^-4 and 3.0×10^-4 Torr. Iron nitrides such as Fe₃N and Fe₄N were detected in this film and the total amount of nitrogen was 3 to 5 at.%. It was confirmed by TEM observation that the addition of nitrogen reduced the grain size of the iron film. The coercive force of this film increased sharply at about 125°C, which corresponds to the Curie temperature of Fe₃N. The decrease of the coercive force in an iron film by the addition of nitrogen may be attributed to the reduction of the grain size and the existence of the magnetic iron nitrides such as Fe₃N and Fe₄N.