Influence of R.F. sputter parameters on the magnetic orientation of Co-Cr layers

Co-Cr layers for the perpendicular recording mode were deposited by means of RF-sputtering. The most important sputter parameters, i.e. the RF sputter high voltage V
RF
, the argon pressure P
ar
and the substrate holder temperature T
sh
, gave an optimum value for perpendicular orientation of the magnetization. The crystal structure is always hcp within the ranges of varied parameters and no other magnetic phases were observed. If the sputter parameters do not have optimum values an additional hcp compound with in-plane orientation of the c-axis is observed. This orientation causes an increase of the in-plane remanence
S//= (M_{r}/M_{s})
. Measurements of the substrate temperature T
s
as an function of the various sputter parameters lead to the conclusion that an exclusive perpendicular c-axis orientation is only obtained at
T_{s} \sim 15\theta\deg
c. At other T
s
established either directly by changing T
sh
or indirectly by changing the sputter conditions an additional hcp compound with in-plane c-axis orientation appears. We concluded that T
s
is the dominant parameter for sputtering CoCr layers.