LAUSR

Abstract Nickel–Copper alternate layers have been a topic of considerable interest due to having several applications in data storage devices, giant magnetoresistive (GMR) sensors and magnetic recording heads. But the continuous use of these devices can initiate damage to their structural integrity because of wear and erosion. Therefore, herein, the selective mixing of carbon nanotubes (CNTs) was engineered either with Ni layer or Cu layer or with both Ni and Cu layers in the electrodeposited Ni/Cu system for enhancing the magnetic susceptibility with the secondary aim of improving the wear resistance of the material. The satellite reflections along with the primary reflections in x-ray diffraction measurements exhibited the configuration of super-lattice structure in the coatings, which are the indicative of multilayered films. Addition of CNT within Ni as well as Cu layer (Ni-CNT/Cu-CNT) shows permanent magnetism with higher magnetic coercivity (749.13 Oe), remanence (0.072 emu/g) and squareness (0.30) when compared to the CNT addition either with Ni (Ni-CNT/Cu 275.20 Oe, 0.011 emu/g and 0.02, respectively) or Cu only (Ni/Cu-CNT 589.71 Oe, 0.027 emu/g and 0.09, respectively) as well as bare Ni/Cu coating (126.89 Oe, 0.007 emu/g and 0.008, respectively). A strong permanent magnetism of CNT added alternate layer was due to the spin transfer between the ferromagnetic Ni and the reinforcing particles. Nonetheless, Ni-CNT/Cu-CNT with high coercivity, remanence and squareness have the maximum transfer of spin between the ferromagnetic catalyst and CNTs due to refined grain structure (23 nm). The significant enhancement in the tribological resistance of Ni-CNT/Cu-CNT (wear rate of 3.57 × 10−3 mm3/Nm) than that of Ni-CNT/Cu (4.00 × 10−3 mm3/Nm), Ni/Cu-CNT (3.94 × 10−3 mm3/Nm) as well as Ni/Cu (12.71 × 10−3 mm3/Nm) was also linked through the reduced contact depth (18.0 μm), contact radius (57.23 μm) and shear stress (0.08 GPa), calculated by different models. Thus, Ni-CNT/Cu-CNT alternate layers with permanent magnetism and restricted wear damage can be a potential coating for giant magnetoresistive sensors.