Magnetic properties of electroless-deposited NiFeB and electrodeposited NiFe alloy thin films

The magnetic properties and the structure of electroless-deposited NiFeB films were investigated in comparison with those of electrodeposited NiFe films. The electroless-deposited NiFeB film with 27at% Fe content had the lowest coercivity, H_c, as low as 0.5 Oe with a saturation magnetic flux density, B_s, of 1.0 T. The saturation magnetostriction, λ_s, and the uniaxial magnetic anisotropy, H_k, were 5.0×10^-6 and 10 Oe, respectively, which were larger than those of the conventional, electrodeposited permalloy film. The permeability of as-deposited Ni₇₀Fe₂₇B₃ film was 1000 at 1 MHz. In order to improve the permeability, the film was heated at 200 °C in a magnetic field applied in the hard-axis direction to decrease the H_k value, and the permeability became 2000 at 1 MHz. The crystal structure and grain size of NiFeB and NiFe films were investigated by XRD, THEED and TEM. Both films with low H_c had an fcc structure; the grain size of the NiFeB film was smaller than 10 nm, while that of the NiFe film was larger, approximately 20 nm. The results suggested that the electroless-deposited NiFeB film had a larger magnetic anisotropy than the electrodeposited NiFe film. Moreover, the films with H_c less than 10 Oe did not show clear difference between their TEM bright images and THEED patterns.