A study on total thickness dependency: microstructural, magnetoresistance and magnetic properties of electrochemically deposited permalloy based multilayers

Abstract

Electrochemically deposited permalloy based NiFe/Cu multilayers, relating their magnetic and magnetoresistance properties with crystal structure and the corresponding film composition were studied as a function of the total film thickness. The permalloy based multilayers were grown on strong (110) textured copper sheets with electrodeposition under potentiostatic control. The total multilayer film thickness was changed from 0.3 to 5 µm while ferromagnetic nickel–iron and nonmagnetic copper layer thickness was kept constant at 3 and 1 nm, respectively. Energy dispersive X-ray analysis revealed that the nickel and iron content of the multilayers decreased and copper content increased as the total film thickness increased. All multilayers exhibited face-centred cubic structure with (110) preferred orientation. The highest peak intensity changed from (220) to (111) when the total thickness was higher than 2 µm. The multilayers exhibited giant magnetoresistance (GMR). The maximum GMR magnitude of ~4 % was obtained for the films with total thickness less than 1 µm and the GMR decreased down to ~1 % with increasing film thickness to 5 µm. The saturation magnetisation and coercivity decreased from 78 to 11 emu/cm3 and from 24 to 12 Oe as the total thickness of the multilayers increased from 0.3 to 5 µm, respectively. The variations in magnetic and magnetoresistive properties related to the microstructure were attributed to the variation of the film contents caused by total film thickness.