Spindle motors in data storage devices such as hard disk drives (HDDs), are required to have higher speed, highly accurate rotational performance and low power consumption. Utilization of a self-acting air bearing has been considered as an alternative of the exisisting precision ball bearings for its bearing system. A self-acting air bearing has not come into practical use partly because the performance of contact start stop (CSS) was not satisfactory. In this paper, we have utilized amorphous hydrogenated carbon (a-C : H) as a thin film lubricant of a self-acting air bearing to study its use from the viewpoint of tribology. A result obtained from the contact start stop testing is as follows : when amorphous hydrogenated carbon (a-C : H) was used on the sliding surface of a self-acting air bearing, it exhibited sufficient performance-[which was high enough to be equal to the required] for HDDs-almost more than 15 times that of liquid lubricant which has traditionally been accepted as surface lubricant for magnetic disks.