Doped Of Sio <sub> 2 </ Sub> Preparation And Physical Properties Of The Cobalt Ferrite Thin Films Research

Cobalt ferrite (CoFe2O4) thin films as a high-density magnetic recording media has high coercivity and magnetocrystalline anisotropy, excellent chemical stability and mechanical hardness. In this thesis, it is mainly investigated the microstructure and magnetic properties of CoFe2-xSixO4 (x = 0,0.1,0.2,0.3) thin films doped SiO₂ , whose growth substrates were Si (100) and MgO (100) .The CoFe2-xSixO4/MgO films were prepared by RF magnetron sputtering, the films are spinel structure,whose crystal orientation is changed by the annealing temperature, The lattice constant of the films decreases with the dosage increase of SiO₂. The magnetic properties of the CoFe2-xSixO4/MgO films are closely related to the annealing temperature and the dosage of SiO₂, with the annealing temperature increasing, the perpendicular coercivity of the films increases first and then decreses, the magnetization inceases, and the curies temperature decreases first and then increases; with the dosage of SiO₂ increasing, the coercivity of the films increases, the saturation magnetization decreases, the remanent magnetization increases, the remanent ratio increases, and the curies temperature increases. The films annealing at 800οC, the coercivity reaches maximum of 758KAm-1; the films annealing at 900οC, the saturation magnetization reaches maximum of 439 KAm-1, the remanent magnetization reaches maximum of 254 KAm-1, and the remanet ratio reaches maximum of 0.717; the films annealing at 400οC, the curies temperature can reach maximum of 515οC.The CoFe2-xSixO4/MgO films prepared by RF magnetron sputtering also have a preferred orientation of the spinel structure, the annealing treatment promotes the films crystallization and grain growth. Si element in the CoFe2-xSixO4/Si films is hingher than in the CoFe2-xSixO4/MgO films due to the Si in Si substrates will diffuse into the cobalt ferrite films during preparation. Compared with the manetic properties of the CoFe2-xSixO4/MgO films, the coercivity of the CoFe2-xSixO4/Si films increases, the saturation magnetization decreases, the remanent magnetization increases, the remanent ratio increases, and the curies temperature increases. The coercivity of the CoFe2-xSixO4/Si films reaches maximum of 824KAm-1, the saturation magnetization reaches maximum of 382 KAm-1, the remanent magnetization reaches maximum of 275 KAm-1, the remanent ratio reaches maximum of 0.86, and the curies temperature reaches maximum of 515οC.