| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 99 === In our earlier research, we found the MOKE signal incident from 45 degree would
cause perpendicular signal to couple with the longitudinal one. To distinguish
the signal from one to another, we arranged 45 degree and 0 degree optical setup
for the measurement of longitudinal and perpendicular respectively. However,
hysteresis loops are only observed in the longitudinal direction.
To measure smaller signal in our experiment, we reduced the noise level by
one order and thus improved the signal to noise ratio. It’s ten times better then
previous result. Under smaller signal or worse S/N ratio condition, we still
measured the MOKE signal.
In order to quantitatively analyze the current-induced field, we made a metal
coil and try to measure the bias produced by the field. And we injected the
reverse current-induced field, , try to counteract the bias of hysteresis loop which
is induced by sample current.
Besides, we also dosed oxygen on the sample and measured the MOKE signal.
There was no change comparing with which is measured in gas-free condition.
But we found the coercivity became larger after annealing to 300K, and the
current-induced bias in oxygen become smaller.
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