Dependence of magnetic properties on magnetic layer thickness in SmCo/Cr films

SmCo/Cr films were prepared with the thickness of SmCo layer varying from 1 to 400 nm, and the dependence of the magnetic properties on SmCo layer thi ckness was studied. Atomic force microscopy (AFM) measurement revealed that both the Cr underlayer and SmCo/Cr films were very similar in surface morp hology with the surface roughness (Ra) of about 6 nm for the SmCo layer thi nner than 100 nm. The Cr underlayer contributes to generate small grain siz e and smooth surface for SmCo layer as well as to improve its magnetic prop erties. The maximum coercivity was about 3.3 kOe, and the squareness and th e coercive squareness in the plane direction were about 0.91 and 0.97, resp ectively, when the SmCo layer thickness was 40 nm. The diameter of switchin g unit estimated by the magnetic switching volume was smaller than 30 nm, w hile AFM observations show a grain size of 50 nm or more. The magnetic prop erties and the microstructure of SmCo/Cr bilayer films promise to be suitab le for high density recording media applications. (C) 1999 American Institu te of Physics. [S0021-8979(99)68708-4].