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Effect of swift heavy ion irradiation in Fe/W multilayer structures

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

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Effect of swift heavy ion irradiation in Fe/W multilayer structures

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  1. Effect of swift heavy ion irradiation in Fe/W multilayer structures Sharmistha Bagchia, S. Potdara, F. Singhb, and N. P. Lallaa 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 1st 2nd 1st 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 Au9+ ion irradiation up to fluence of 4×1013 ions/cm2. 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). IRRADIATION - STUDIES INTRODUCTION 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]. 10nm 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]. (a) 10nm (a) FeW10 FeW30 W(400) W(321) W(220) W(211)/Fe(200) W(200) W(211) W(110)/Fe(110) Fe(200) W(110)/Fe(110) (b) INTRODUCTION OF SWIFT HEAVY ION IRRADIATION (b) FeW10 Irradiated Energetic Ions FeW30 Irradiated 2nd W(400) W(321) 1st W(220) W(211) Electronic Energy Loss (dE\dx)e W(200) Nuclear Energy Loss (dE\dx)n W(110)/Fe(110) This dominates at an energy of 1 MeV or more 10nm This dominates at an energy of 1 keV (c) (d) FeW20-5BL FeW20 Irradiated 2nd FeW20 W(211) 1st 1st W(200) W(211) W(200) Reflectivity W(110)/Fe(110) Coulomb Explosion Thermal Spike Model W(110)/Fe(110) 1st Irradiated MLS 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 Au9+ ions at fluences between 5×1012 to 4×1013 ions/cm2. 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. (f) (e) 20nm (e) (f) 20nm FeW10-5BL-Si FeW30-5BL-Si FeW20-5BL-Si CONCLUSION • 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. Multilayer Structure Coercivity Hc (Oe) Saturation Field Value (Oe) FeW10- Pristine 82 460 (c) 10nm FeW10- 5×1012 59 329 REFERENCES • 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 C19, (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. FeW10- 4×1013 68 591 W(211) FeW30- Pristine 132 584 W(110)/Fe(110) FeW30- 5×1012 42 354 FeW30- 4×1013 101 527 Magnetic Field (Oe) E-mail–bagchi.sharmistha@gmail.com www.csr.ernet.in (d)

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