1. Effect of swift heavy ion irradiation in Fe/W multilayer structures Sharmistha Bagchi a, S. Potdar a, F. Singh b, and N. P. Lalla a a) UGC-DAE Consortiums for Scientific Research, Khandwa Road, Indore 452001. INDIA b) Inter University Accelerating Center (IUAC), Aruna Asaf Ali Marg, New Delhi 110067. INDIA Abstract The present study reports the effect of swift heavy ion irradiation on structural and magnetic properties of sputtered Fe/W multilayer structures (MLS) having bilayer compositions of [Fe(20Å)/W(10Å)] 5BL and [Fe(20Å)/W(30Å)] 5BL. These MLS were subjected to 120 MeV Au 9+ ion irradiation up to fluence of 4×10 13 ions/cm 2. Pristine and irradiated MLS were subjected to structural and magnetic characterization employing wide-angle x-ray diffraction (WAXD), cross-sectional transmission electron microscopy (X-TEM) and magneto optical Kerr effect (MOKE). Tailoring the properties of functional materials at atomic scale represents the ultimate goal in material science research. The most desirable approach is to artificially fabricate the structures with atomic precision, i.e. in layer-by-layer growth. For GMR application interface quality plays a decisive role in achieving the optimum performance. In order to optimize and understand these properties; structural studies regarding interface stability, against swift heavy ion-irradiation are done. To the best of our knowledge there is almost no reports of swift heavy ion irradiation study on immiscible systems like W/Fe [1, 2]. E-mail –bagchi.sharmistha@gmail.com EXPERIMENTAL-DETAILES W/Fe multilayer with composition [W(10,20,30) Å /Fe(20) Å ] ×5BL were deposited on Si-substrates by ion beam sputtering technique. The sample were irradiated by 120 MeV Au 9+ ions at fluences between 5×10 12 to 4×10 13 ions/cm 2. The irradiation was performed using the 15UD Pelletron accelerator at IUAC, New Delhi.The specimens were characterized before and after irradiation, using WAXD, XRR, X-TEM and MOKE. E. Majkova, S. Luby, M. Jergel, A. Anopchenko, Y. Chushkin, G. Barucca, A. Cristoforo, P. Mengucci, E. D. Anna, A. Luches, M. Martino and H. Y. Lee Materials Science and Engineering C 19, (2002) 139. E. Majkova, S. Luby, M. Jergel, Y. Chushkin, E. D. Anna, A. Luches, M. Martino, P. Mengucci, G. Majni, Y. Kuwasawa and S. Okayasu Applied Surface Science 208, (2003) 394. S. Bagchi and N. P. Lalla, Thin Solid Films 515, (2007) 5227. S. Bagchi, S. Potdar, F. Singh and N. P. Lalla J. App. Phys. 102, (2007) 074310. S. Bagchi and N. P. Lalla. J. Phys.: Condens. Matter 20, (2008) 235202. www.csr.ernet.in IRRADIATION - STUDIES The W-Fe system, with increasing bilayer thickness shows a weakly textured multilayer structure consisting of W layers oriented along [110] direction. The SHI affects the inter-layer and intra-layer features in different ways. On irradiation the Fe-layers of the multilayer recrystallized of the individual layers into randomly oriented nano-crystals. MOKE results show the change in coercivity and saturation value with irradiation dose, which is also consistence with the X-TEM data. For direct observation and better understanding of the irradiation-induced microstructural changes, plane and cross-sectional TEM investigation on pristine as well as irradiated multilayer of W/Fe was carried out The observed alternate black and white layer- contrast is Z-contrast due to W and Fe layers [3, 4, 5]. INTRODUCTION OF SWIFT HEAVY ION IRRADIATION REFERENCES CONCLUSION INTRODUCTION This dominates at an energy of 1 keV This dominates at an energy of 1 MeV or more Electronic Energy Loss (dE\dx)e Nuclear Energy Loss (dE\dx)n Thermal Spike Model Energetic Ions Coulomb Explosion Magnetic Field (Oe) FeW10-5BL-Si FeW20-5BL-Si FeW30-5BL-Si Reflectivity 527101FeW30- 4×10 13 35442FeW30- 5×10 12 584132 FeW30- Pristine 59168FeW10- 4×10 13 32959FeW10- 5×10 12 46082 FeW10- Pristine Saturation Field Value (Oe) Coercivity H c (Oe) Multilayer Structure FeW20-5BL W(220) W(110)/Fe(110) W(200) W(211)/Fe(200) W(321) W(400) (b) (a) 1 st 10nm 1 st (c) 10nm W(220) W(211) (d) W(110)/Fe(110) W(200) W(321) W(400) W(110)/Fe(110) W(200) W(211) (f) (a) 1 st 2 nd 10nm (d) W(110)/Fe(110) W(211) W(110)/Fe(110) Fe(200 ) W(211) (b) W(110)/Fe(110) W(200) W(211) (f) (c) 10nm 1 st 2 nd (e) 20nm 1 st (e) 20nm 1 st 2 nd Irradiated MLS FeW10 Irradiated FeW20 Irradiated FeW30 Irradiated FeW30