High quality Cu–Co alloy ﬁlms with excellent metallic luster have been electrolytically deposited directly onto n-Si (1 0 0) substrate, thereby eliminating the need of a conducting seed layer, which is otherwise required when the ﬁlms
were grown on insulating substrates (Al2O3). The as-deposited Cu–Co ﬁlms exhibit relatively higher magnetoresistance
(MR) in comparison with the as-deposited ﬁlms on Al2O3 under identical conditions. The observed increase in MR could be attributed to the reduced substrate current shunting. The MR further improves to 2.67% (at H = 10 kOe) with vacuum annealing (at 4251C for 30 min) of the ﬁlms on Si. This has been ascribed to the separation of Cu and Co phases resulting in a magnetic granular nanostructure. This value of MR of annealed ﬁlms on Si is, however, lower in
comparison with the value obtained for annealed ﬁlms deposited on Al2O3. Glancing angle X-ray diffraction (GAXRD) has revealed the formation of copper silicide in these samples, which is responsible for the lower value of MR. Thus we have observed good MR with a copper silicide host matrix.