Magnetoresistance and Magnetic Relaxation of La-Sr-Mn-O Films Grown on Si/SiO2 Substrate by Pulsed Injection MOCVD

The results of magnetoresistance (MR) and resistance relaxation of nanostructured La1-xSrxMnyO3 (LSMO) films with different film thicknesses (60-480 nm) grown on Si/SiO2 substrate by the pulsed-injection MOCVD technique are presented and compared with the reference manganite LSMO/Al2O3 films of the same thickness. The MR was investigated in permanent (up to 0.7 T) and pulsed (up to 10 T) magnetic fields in the temperature range of 80-300 K, and the resistance-relaxation processes were studied after the switch-off of the magnetic pulse with an amplitude of 10 T and a duration of 200 mu s. It was found that the high-field MR values were comparable for all investigated films (similar to-40% at 10 T), whereas the memory effects differed depending on the film thickness and substrate used for the deposition. It was demonstrated that resistance relaxation to the initial state after removal of the magnetic field occurred in two time scales: fast' (similar to 300 mu s) and slow (longer than 10 ms). The observed fast relaxation process was analyzed using the Kolmogorov-Avrami-Fatuzzo model, taking into account the reorientation of magnetic domains into their equilibrium state. The smallest remnant resistivity values were found for the LSMO films grown on SiO2/Si substrate in comparison to the LSMO/Al2O3 films. The testing of the LSMO/SiO2/Si-based magnetic sensors in an alternating magnetic field with a half-period of 22 mu s demonstrated that these films could be used for the development of fast magnetic sensors operating at room temperature. For operation at cryogenic temperature, the LSMO/SiO2/Si films could be employed only for single-pulse measurements due to magnetic-memory effects.