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Nonepitaxial FePt: X films (X =Cu,Au,CuAu) with tunable magnetic properties are fabricated and investigated. Emphasis is on controlling and adjusting the magnetic properties of high-density perpendicular recording media through exchange decoupling and anisotropy. The films are initially deposited as multilayers with the structure [FePtX]n and have individual thicknesses from about 0.06 to 1.1 nm. To create an (001)-oriented granular L10 structure, the films are then annealed at temperatures of 600 °C for 5 min and 550 °C for 10 min. The data indicate that Cu enters the L10 lattice whereas Au segregates at the grain boundaries and reduces the intergranular exchange coupling. For X=CuAu, we obtain coercivities Hc below 10 kOe, and slopes α =(dMdH)Hc of about 1. For X=Cu, we find a favorable reduction in Curie temperature and Hc.