In-situ measurements of magnetic properties in vacuum-deposited permalloy films

The quasi-static magnetic properties of vacuum-deposited Permalloy films of zero-magnetostrictive composition are examined in situ in an evaporator equipped with a laser-operated Kerr magneto-optic hysteresigraph. The coercive force, whicho depends strongly upon the film thickness, is large (Hc > 20 Oe) when the hysteresis loop is first observable with a thickness of ∼ 50 A for low substrate temperatures (T 100°C). There are two peaks of coercivity, at ∼400 A and ∼1,000 A; the two are thought tob e related, respectively, to the transitions from the Neel to the cross-tie walls, and from the cross-tiet o the Bloch walls. Two distinct components of the uniaxial anisotropy field are identified, both of which are characteristic of fabrication parameters: K1, which is difficult to re-orient once the anisotropy is induced; and K2, which is readily re-oriented (with time constant lessth an 10 sec) along any angle between the easy and the hard axis. The net anisotropy field and the easy-axis orientation, both of which are affected by the K2 components, can be calculated for a given set of fabrication parameters. Experimental results agree well with the calculated values. The angular dispersion does not appear to be affected by the amplitude of the orienting field H or the nature of the field (ax. or d.c.) when H > Hc. There is a slight increase in angular dispersion as the K2 component of the anisotropy rotates from the easy to the hard axis.