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

Present study reports effect of swift heavy ion irradiation on structural and magnetic properties of sputtered W/Co multilayer structures (MLS) having bilayer compositions of [W(10 Å)/Co(20 Å)]_5BL and [W(20 Å)/Co(20 Å)]_5BL. These MLS are irradiated by 120 MeV Au⁹⁺ ions up to fluence of 1 × 10¹³ ions/cm². X-ray reflectivity (XRR), wide-angle X-ray diffraction (WAXD), cross-sectional transmission electron microscopy (X-TEM) and magneto optical Kerr effect (MOKE) techniques are used for structural and magnetic characterization of pristine and irradiated MLS. Analysis of XRR data using Parratt’s formalism shows a significant increase in W/Co interface roughness. WAXD and X-TEM studies reveals that intra-layer microstructure of Co-layers in MLS becomes nano-crystalline on irradiation. MOKE study shows slight increase in coercivity at higher fluence, which may be due to increase in surface and interface roughness after recrystallization of Co-layers.