Perpendicular magnetic anisotropy and structural properties of NiCu/Cu multilayers

Perpendicular magnetic anisotropy (PMA) was studied at low temperature (T=30 K) in dc-magnetron sputtered Ni60Cu40/Cu multilayers. PMA has been observed in many multilayer structures for ferromagnetic layer thicknesses less than a certain thickness tperpendicular. In general cases tperpendicular is less than a few nanometers, making such structures unsuitable for low-cost fabrication techniques. Our results show a strong perpendicular easy direction of magnetization for NiCu layer thickness between 4.2 nm and 34 nm. The thickness tperpendicular at which the multilayers change the preferential orientation from perpendicular to in-plane is estimated to be 55 nm. Structural studies show that the low magnetostatic energy density is likely to be the main reason for the large tperpendicular value obtained in this system