High negative tunneling magnetoresistance in magnetic tunnel junctions with a ferrimagnetic CoFe-Gd electrode and a CoFe interface layer

Ferrimagnetic rare earth-transition metal alloys can display negatively spin polarized current and thus give rise to negative tunneling magnetoresistance in magnetic tunnel junctions. We show that a thin (∼15 Å) ferromagnetic transition metal interlayer at the tunnel barrier interface can greatly enhance the negative magnetoresistance. By adjusting the relative thicknesses of the ferrimagnetic and ferromagnetic layers the coercivity can be varied by more than a hundredfold. The interface layer also significantly increases the temperature at which the device undergoes electrical breakdown. © 2006 American Institute of Physics.