The magnetic properties of granular Co_25Cu_75/Cu multilayer films prepared by sputtering onto heated glass substrates have been investigated in the range of ultrathin alloy films (5-250A) and Cu spacer thicknesses (0-50A). Both the coercive field at 10 K and the maximum superparamagnetic blocking temperature T_B are found to be sensitive to finite-size effects in single-layer films, and to interactions between layers in multilayer films.Our results indicate that the magnetic properties of granular alloy layers can be engineered to a large extent by selectively modifying the local environment of the Co particles.
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