Stress Measurements in Materials for Magnetic Recording
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STRESS MEASUREMENTS IN MATERIALS FOR MAGNETIC RECORDING V. Raman, K.R. Coffey, R. Umphress and .T.K. Howard IBM - ADSTAR, San Jose, CA 95193.
ABSTRACT Investigations of the mechanical behavior of materials used in magnetic recording is of considerable practical importance in order to assure reliable file performance. With this objective, we have investigated the magnitude of the internal stresses observed in four sputtered thin film materials typically used in magnetic rccording. First, the magnitude of the stresses observed in sputtered carbon films with and without hydrogen were measured and the nature of stress relaxation and thermal stability in dif[ercnt ambicnts were investigated. Second, the magnitude of the internal stress in Col'tCr magnetic media with and without a Cr-based sublayer that enhances magnetic performance was examined. Finally, the magnitude of stresses typically observed in thicker sputtered films of' alumina were investigated both at room temperature and at elevated temperatures. The magnitude of the stresses observed in these sputtered films and their influcnce on mechanical performance are discussed. 1. INTRODUCTION There is continuing interest in investigating the mechanical properties of the wide variety of materials used in the magnetic recording industry because or its direct relevance to file performance and reliability. A common feature between thin film materials applications in the microelectronics industry and in the recording industry is the use of complex multilayered structures of thin metal or non-metal films dcpositcd on different substrates. Typically, in thin film disk applications, a rigid Al alloy disk is clectrolcss plated with a coating of Ni-P for wear resistance [1]. The magnetic media and a protective overcoat film are then sequentially deposited over the disk substrate. The magnetic media is normally a Co based alloy[2]. Several different types of protective disk overcoats have been investigated and the use of sputtered carbon films as a disk overcoat is widespread [1]. The mismatch in the thermal and mechanical properties of these materials, the adhesion of the films both to the substrate and to the magnetic layer and the microstructure and mechanical behavior of these films are all of much interest. Also, the nature and magnitude of the internal stresses present in these films are of direct interest as they can influence both adhesion and tribological performance. The reported work concerns the nature and magnitude of the internal stresses observed in four different thin film materials of interest in the magnetic recording industry. As is well recognized, the magnitude of the internal stresses is largely dictated by the process conditions used in thin film deposition and the objective here is to merely document the nature and magnitude of the stresses typically observed. An additional focus of this work is to examine the influence of temperature on the magnitude of the internal stress as well as to investigate the fiature of the stress relaxation processes that o
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