MAGNETIC-PROPERTIES AND GIANT MAGNETORESISTANCE OF FE AU MULTILAYERS/

Magnetic properties and magnetoresistance (MR) are examined for the Fe /Au multilayers (MLs) prepared on glass substrates by electron-beam ev aporation techniques as a function of the thicknesses of Fe and Au lay ers: d(Fe) and d(Au). For small d(Fe), the perpendicular magnetic anis otropy is induced, and in the films of d(Fe)approximate to 5 Angstrom, the stripe magnetic domain patterns are observed. In d(Fe)less than o r equal to 3 Angstrom, however, a superparamagnetic nature and a granu lar-type giant magnetoresistance (GMR) appear at room temperature. In a series of [Fe(3 Angstrom)/Au(d(Au))](40) MLs, the MR ratio increases with d(Au) and reaches the first peak at around 10 Angstrom. On the o ther hand, at 14 K, the ferromagnetic component having a perpendicular anisotropy becomes dominant, and the GMR arises from the random wall alignment due to the antiferromagnetic coupling between the adjacent F e layers, causing the first MR peak at d(Au)approximate to 10 Angstrom . The layered structure is obscured and the superparamagnetic Fe grain s are created by annealing at 300-350 degrees C, followed by the cryst alline growth upon annealing at temperatures above 350 degrees C. Thes e variations in the film morphology cause the changes in the saturatio n magnetization and the MR ratio. (C) 1997 American Institute of Physi cs. [S0021-8979(97)01121-3].