The Study Of Magnetic Structure And Magnetic Properties Of Amorphous Films With Perpendicular Anisotropy

Amorphous Nd-Fe-B films are prepared on Si substrates by dc magnetron sputtering. The influence of sputtering conditions (sputtering air pressure, sputtering temperature and substrate temperature) on the morphology structure and magnetic properties of the films has been studied, as well as the discussion about the influence of sputtering temperature and film thickness on the direction of easy axis of amorphous Nd-Fe-B films with perpendicular anisotropy. The results showed that the value of magnetocrystalline anisotropy of the films will change obviously with the changing of the sputtering air pressure and temperature, which has a direct influence on the magnetic properties of the film. In addition, surface structure and magnetic properties of the film are also determined by the substrate temperature. In our experiments, films prepared at 250℃ with Ta substrate fabricated at 25℃ has rough surface and stripe domain structure, while films prepared at 250℃ with Ta substrate fabricated at 400 ℃ has smooth surface and labyrinthine domain structure. The influence of sputtering temperature and film thickness on the magnetic properties of the film can be attributed to the interplay of magnetocrystalline anisotropy and shape anisotropy. Experiment results showed that the magnetic domain structure for film with 150 ℃ sputtering temperature and 200nm thickness(smaller magnetocrystalline anisotropy energy and larger shape anisotropy energy) has changed significantly with the applied magnetic field and form stripe domains arranged along the direction of the field because the direction of easy axis is closing to the film plane. While, for the film with 300℃ sputtering temperature and 600nm thickness(larger magnetocrystalline anisotropy energy and smaller shape anisotropy energy), magnetic domain structure is hardly varied with applied field. This result has a certain significance in the area of magnetic recording material. Finally, we investigated the magneto-optical characteristics of the amorphous Nd-Fe-B films and find out that the polar magneto-optical Kerr rotation increased with the decrease of the incident wave length, even appears a maximum rotation of 0.5°at the wavelength of 440nm. So it has a certain application value due to its obvious Kerr effect at short wavelength.