Abstract
Tunnel magnetoresistance (TMR) has been investigated in single (Ni-Fe/Al2O3/Co) and double (Ni-Fe/Al2O3/Co/ Al2O3/Co) tunnel junctions. The Al2O3 layer was formed by a direct sputtering method with an Al2O3 target. Metal masks were used to form a cross pattern geometry. In the single junctions the dependence of the tunnel resistance and the TMR ratio on the Al2O3 thickness was investigated. The tunnel resistance increased exponentially with increasing the Al2O3 thickness. A maximum TMR ratio was 4-5 %. In the double junctions the dependence of the tunnel resistance and the TMR ratio on the thickness of central Co layer was investigated. The tunnel resistance decreased with increasing the Co thickness. The maximum TMR ratio was 2%, which was smaller than the value of the single junctions.
