X-ray analysis of thin film structures used in magnetic sensors and magnetic media

C. Schug

Naomi technologies AG, Hechtsheimerstr. 2, D-55131 Mainz, Germany

The performance of multilayer stacks used in magnetic devices such as giant-magnetoresistive (GMR) sensors and magnetic media is intimately linked to the physical properties of the contributing functional films as well as to their crystalline and interfacial structure. A number of surface-sensitive X-ray methods to investigate these parameters is presented. Specular X-ray reflectometry (XRR) has proven to be an absolute method to measure film thicknesses in complicated layer sequences - as e.g. the Ru-nanolayer thickness in GMR stacks - and deposition rates with sub-Angstrom accuracy [1]; it can be used for the routinely offline monitoring of large-area coupons, but also for the calibration of quicker, indirect, inline monitoring methods, e.g. X-ray fluorescence (XRF). Off-specular XRR was successfully applied to monitor the interfacial properties of ion-bombarded Co/Pt-superlattices, a promising candidate for perpendicular recording based on the so-called patterned media approach [2,3]. In-plane X-ray diffraction (XRD) has gained increasing attention with regard to the study of the real structure (crystallite size, preferred orientation, stress) of functional thin films. The method is well-suited to investigate phase transitions in thin films, such as the fcc to fct transition of a GMR sensor's PtMn pinning layer upon annealing [4].

[1] C. Schug, B. York, J. Marien, H.-R. Blank, Advances in X-ray Analysis, Vol. 44 (2001), 295-301

[2] A. Dietzel et al., Mat. Res. Soc. Symp., Vol. 705 (2002), Y3.4.1- Y3.4.11

[3] C. Schug, H. Grimm, R. Berger, A. Dietzel, M. Wormington, to be published, Surf. Interface Anal. 36 (2004)

[4] R. M. Oeksuezoglu, C. Schug, B. York, to be published, JMMM