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Low energy ion beam assisted deposition of a spin valve

2007; American Institute of Physics; Volume: 101; Issue: 7 Linguagem: Inglês

10.1063/1.2715751

1520-8850

J.J. Quan, Stefan Wolf, H.N.G. Wadley,

Ion-surface interactions and analysis

The spin dependent electron transport in giant magnetoresistive (GMR) multilayers is significantly affected by the atomic scale structure of their interfaces. Devices with atomically flat and chemically sharp interfaces are preferred for magnetic sensor and memory applications. Recent atomic simulations of the atom-by-atom assembly of these devices indicate that near optimal interfacial structures can be created using low energy, ion assisted vapor deposition techniques with ion energies in the 5–10eV range. A recently developed biased target ion beam deposition system has been used to experimentally test this hypothesis. Prototypical Ta∕NiFe∕Co∕Cu∕Co∕FeMn∕Cu spin valve structures were first grown using (simultaneous) argon ion assistance during deposition of the Co∕Cu∕Co trilayer part of the spin valve multilayer. Assisting ion energies of around 10eV resulted in structures with a 30% higher magnetoresistance ratio and significantly reduced coupling field compared to samples grown with no ion assistance or with ion energies above 15eV. These results are consistent with the atomistic simulation predictions. Other promising ion assistance schemes identified by the simulations were then used to deposit the Ta, NiFe, FeMn, and the top copper layer. A near optimal strategy was identified that resulted in the further improvement of the GMR ratio.