Magnetic properties and thermal stability of Fe-Zr-N/Si-N and Fe-Ta-N/Si-N multilayer film (abstract)

It has been shown that Fe-N/Si-N multilayer films has excellent soft magnetic properties, but their properties are deteriorated easily by increasing the temperature above 400 degree C.1 In this study, we added a small amount of Zr and Ta to the Fe-N layer to improve their thermal stability of the soft magnetic properties. Multilayer films about 3000 A thick were deposited by an opposed target sputtering apparatus on glass slide substrates. Thickness of the Si-N layer was fixed at 50 A, while those of the Fe-Zr-N (or Fe-Ta-N) layer TFe-N was changed in the range from 200 to 1000 A. For control of the film composition, a composite target was used. The area ratio of the Zr (or Ta) plate to total target area was changed in the range 0∼4.8%. Figure 1 shows the changes in coercivity Hc and saturation magnetization Ms of the Fe-Zr-N/Si-N film with annealing temperature. The changes in x-ray diffraction patterns of these films are shown in Fig. 2. It is evident from these figures that the crystal growth in the films obtained by the sputtering of 4.8%: Zr-Fe target is significantly suppressed, though the film obtained by the sputtering of 3.2%: Zr is crystallized at a temperature below 400 degree C. Soft magnetic properties of the 4.8%: Zr film are not deteriorated by the annealing at the temperature up to 550 degree C. Saturation magnetization has a tendency to increase as the annealing temperature increases. Similar results are obtained in the addition of Ta