Magnetically tunable spin-polarization of the current through a double quantum dot device

We theoretically study the spin-dependent transport in a double quantum dot device connected with normal-metal and ferromagnetic leads by using the nonequilibrium Green's function method. In the absence of an external magnetic field, the current polarization is zero for a range of positive bias, while it is a relatively large value for a negative bias. In the presence of an external magnetic field perpendicular to the magnetization of the lead, the spin-flip effects make the current spin-polarized for both of the positive and negative bias. Thus the device can operate as a magnetically tunable spin-polarized current diode.