| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 102 === Perovskite La_(1-x) Sr_x MnO_3 (LSMO) has been demonstrated to exhibit rich emergent physics, such as colossal magnetoresistance and phase separation phenomena, owing to the strong correlations among the charge, spin, orbital, and lattice degree of freedoms. The latest article pointed out that the magnetic domain observed from magnetic force microscopy (MFM), which showed two different magnetic domain when applied an in-plane magnetic field. The hysteresis loop also appeared a two-step saturation when applied an out of plane magnetic field by vibrating sample magnetometer (VSM) measurement. In this article, there is a theoretical model to explain the special magnetic domain structure. Finally, they predict the angle between the easy axis and the plane normal is 37° through the theoretical calculation.
In our research, the experiments are divided into two parts. First, circular LSMO films (120 nm) grown on SrLaAlO_3(001) (SLAO) substrates by the pulsed laser deposition (PLD) method were used to reappear the special magnetic domain structure. By comparing the results from SQUID, VSM and FMR measurements, the expected special magnetic domain structure did not appear. We will discuss the possible reasons that caused the observed discrepancy. Second, we used VSM and FMR by varying the angle between the easy axis and the plane normal to verified the prediction in the theoretical calculation. Then we did the low temperature FMR measurement to observe the magnetic moment behavior. And the spin wave caused by microwave can also provide the spin-wave stiffness and magnetic domain wall stiffness from the energy dispersion relation, which can help us to understand more about LSMO from the other side.
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