Control of Critical Current of Intrinsic Josephson Junctions Due to Spin Injection

We have investigated the influence of the ferromagnet magnetization on the critical current I
_c
of the intrinsic Josephson junctions (IJJs) in Co/Au/Bi
₂
Sr
₂
CaCu
₂
O
_y
(BSCCO) mesa structures under applied magnetic fields parallel to the layer. The mesa structure with lateral dimensions of 5×5 μm
²
and 2×13 μm
²
were fabricated by using electron beam lithography, photolithography and Ar ion milling. Before an application of magnetic field B, the current-voltage characteristics of the mesa showed the typical multiple resistive branches with hysteresis similar to those of conventional IJJs. However, by applying B the I
_c
was considerably suppressed and the I
_c
-B curve showed hysteresis in contrast to conventional IJJs. Furthermore, the suppression of I
_c
was found to be minimized at the coercive filed of the Co layer. This implies that the I
_c
is significantly affected by the domain structure of the Co formed on IJJs. From these results we found that the I
_c
of IJJs in the Co/Au/BSCCO mesa can be control by small magnetic field and the hybrid structure of ferromagnet and IJJs might be applicable for a switching device and other spintronics devices.