Finite-size effects in amorphous Fe 90 Zr 10 /Al 75 Zr 25 multilayers

The thickness dependence of the magnetic properties of amorphous Fe90Zr10 layers is explored using Fe90Zr10/Al75Zr25 multilayers. The Al75Zr25 layer thickness is kept at 40 angstrom, while the thickness of the Fe90Zr10 layers is varied between 5 and 20 angstrom. The thickness of the Al75Zr25 layers is sufficiently large to suppress any significant interlayer coupling. Both the Curie temperature and the spontaneous magnetization decrease nonlinearly with decreasing thickness of the Fe90Zr10 layers. No ferromagnetic order is observed in the multilayer with 5-angstrom Fe90Zr10 layers. The variation of the Curie temperature T-c with the Fe90Zr10 layer thickness t is fitted with a finite-size scaling formula [1 - T-c(t)/T-c(infinity)] = [(t - t')/t(0)](-lambda), yielding lambda = 1.2, and a critical thickness t' = 6.5 angstrom, below which the Curie temperature is 0.