Annealing effect on magnetic characteristics on (La,Sr)MnO3 sputtered films

A perovskite type of (La,Sr)MnO₃ films were deposited on SiO₂/Si substrates with amorphous surface by using the facing targets sputtering apparatus. Although the film as-deposited at P(O₂) of 0.3 mTorr was not fully crystallized and the MR ratio was as small as 0.03% at the applied field of 5 kOe, it increased up to 2.5% for the film post-annealed at 850°C in air for 10 min. The partial O₂ pressure P(O₂) strongly affected their crystallinity as well as the Mn content C_Mn. The film as deposited at P(O₂) of 0.03 mTorr was composed of crystallites with excellent (100) orientation at relatively low substrate temperature T_s up to 500°C and the large MR ratio of 3.8% was attained even at room-temperature measurement. Since this MR response exhibits excellent linearity, these LSMO films seem to be applied for magnetic sensor devices. It is clarified that the annealing process in preparation of LSMO film effectively increases the MR ratio of the film with insufficient crystallinity, and is not effective for the fully crystallized film