Influence of intermediate Ag layer on the structure and magnetic properties of Pt/Ag/Fe thin films

Layered films of Pt(15 nm)/Ag(x)/Fe(15 nm) with various Ag layer thicknesses (0 nm, 3 nm, 30 nm) were deposited at room temperature onto SiO2(100 nm)/Si(001) substrates. The films were post-annealed in the temperature range of 100 °C-900 °C for 30 s in high vacuum. The influence of the Ag interlayer on the L10-FePt phase formation, as well as its structure and magnetic properties were investigated by X-ray diffraction, electrical resistance measurements, secondary neutral mass spectrometry and SQUID magnetometry. It is illustrated that the limited solubility of Ag in the FePt lattice as well as its grain boundary segregation and diffusion results in magnetic isolation of the FePt grains and in increase of the coercivity of the film. Sufficient distinctions of L10 phase formation in Pt/Ag/Fe films compared to the FePt/Ag/FePt films were shown. The presence of the Ag interlayer, as compared to the Pt/Fe bilayer, did not change the transformation temperatures, but the increase of the Ag interlayer thickness up to 30 nm resulted in the slowing down of the transformation kinetics: the Ag interlayer acts as diffusion barrier against of the intermixing of the Pt and Fe layers.