Microstructural study of ion-beam deposited giant magnetoresistive spin valves

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Abstract
Detailed microstructural investigation of ion beamdepositedgiant magnetoresistance(GMR)spin valves has been carried out using various techniques of transmission electron microscopy(TEM) and x-ray diffraction. Two fcc phases, i.e., FeMn and NiFe/Co/Cu/Co/NiFe have been identified in ion-beamdepositedTa (50 Å)/FeMn (80 Å)/NiFe(30 Å)/Co(15 Å)/Cu(33 Å)/Co(15 Å)/NiFe(60 Å)/Ta(25 Å)/Si(001) spin valves. The Tabuffer layer is amorphous, while the 50-Å-thick Ta cap layer consists of a 25-Å-thick amorphous layer and on top of which a Ta oxide layer. The lattice constants of the fcc FeMn and the fcc NiFe/Co/Cu/Co/NiFe increase with the ion-beam voltage. Both the FeMn and the NiFe/Co/Cu/Co/NiFe layers are (111) textured. The misfit strain between the FeMn layer and the pinned NiFe layer is released by the formation of dome shape FeMn surface rather then by the formation of misfit dislocations at the interface between the two layers. The peak to valley height of the domes seems to have little effect on the GMR properties of the ion-beamdepositedspin valves. It was found that large columnar grain width gives large exchanged field and ΔR/R of the spin valves.