Magnetic and optical properties of thin films in the system 1-xFe3O4·xFe8/3O4

The magnetic and optical properties of thin films prepared by chemical vapor deposition in the system (1-x)Fe
3
O
4
.xFe
8/3
O
4
are a strong function of x. In particular, the coercive field increases significantly with x. Considering the solid solution of magnetite and λ-Fe
2
O
3
as a defect vacancy form of magnetite, Fe
³⁺
[Fe
³⁺
1+2δ
Fe
²⁺
1-3δ
box$^b$
δ
]O
4
where δ = x/3, it is suggested that the increase in H
c
with x is due to a Fe
²⁺
-
box$^b$
interaction producing a preferred alignment of the vacancy on an octahedral site, which in turn would produce an additional uniaxial anisotropy superimposed on the cubic anisotropy. This interpretation is supported by the observed variation of H
c
with time for compositions within the system. The optical absorption coefficient at 0.63 μm and the optical Faraday effect also are functions of the value of x. The decrease in α with x is associated with the decrease in Fe
²⁺
content, while the decrease in θ is associated with the near equality of the opposing contribution to the rotation of the Fe
³⁺
ions on the octahedral and tetrahedral sites, respectively. Thin films of compositions in the above system have been deposited on glass disks suitable for disk-file applications. Typical recording outputs are shown.