He-RBS, He-ERDA and heavy ion-ERDA analysis of Si/Ta 70 A/CoFe 35 A/HfAlOx/CoFe 35 A/Ta 30 A systems

Low resistance spin-dependent tunnel junctions are investigated for read-head applications due to their large tunnelling magnetoresistance effect and low junction resistance-area product. Typical full junction structures can be Ta 70 A/NiFe 70 A/MnIr 80 A/CoFe 35 A/HfxAlyOz 10 A/CoFe 35 A/NiFe 40 A/Ta 30 A, annealed to temperatures up to 250 deg. C. We analyzed simpler structures with RBS experiments at a grazing angle of incidence in order to study the junction only. Heavy ion- and He-ERDA experiments were also done. The composition of the HfAlO barrier is determined, showing that a slightly substoichiometric oxide is formed. On annealing at 240 deg. C, the interfaces of the barrier become sharper. TEM results confirm that the barrier is continuous after annealing. This is related to an increase in the tunnel magnetoresistance signal from 4% to 13.5% after annealing