Magnetic Exchange-Coupled Sm(Co,R)/Cr (R = Al, Si, Ti, Nb, Cu) Series Films for Ultrahigh-Density Longitudinal Recording Media

SmCoR (R=Al,Si,Ti,Nb,Cu)/Cr series films were fabricated as one kind of promising materials for the ultrahigh density longitudinal magnetic recording media. The Sm(Co,Al,Si)/Cr thin films with coercivity up to 2.36 kOe, squareness ratio S near 0.94 and coercive squareness ratio S^* about 0.9 were obtained. The Cr interlayer caused magnetic decoupling in Sm(Co,Al,Si)/Cr/Sm(Co,Al,Si) thin films. High coercivity of 3400--3840\,Oe and extremely fine grain size of 5-8 nm for the magnetic layer were examined. Using different substrate bias among the Sm(Co,Al,Si)(deposited with substrate bias of -150 V)/Sm(Co,Al,Si)(deposited with no substrate bias)/Sm(Co,Al,Si)(deposited with substrate bias of -150 V), the multilayer exhibited high coercivity of 2960 Oe and S^* of 0.96. Sm(Co,Al,Si)/Sm(Co,Ti,Cu)/Sm(Co,Nb,Cu) trilayer improved matching between the magnetic layer and the Cr underlayer, and led to increasing in-plane anisotropy, high coercivity of 3280 Oe and S^* of 0.92. Lattice matching of SmCoR 1121 and Cr 110, etc. were found under various conditions. The microstructures of these four kinds of medium were also examined. The results suggest that it is possible to produce Sm (Co,Al,Si,Ti,Nb,Cu) multi-layer media with the combined magnetic properties required for the ultrahigh density magnetic recording.