The influence of nano-oxide layer on magnetostriction of sensing layer in bottom spin valves

The magnetostriction coefficient (lambda(s)) of ultrathin sputtered polycrystalline as-deposited and annealed Ta/Ni81Fe19(t)/Ta films was studied as a function of the thickness. lambda(s) and magnetoresistance (MR) of bottom-type spin valves (SVs) with nano-oxide layer (NOL) added in the pinned layer were investigated by using NiFe, Co90Fe10, and CoFe/NiFe/CoFe layers as free layer (FL), respectively. lambda(s) of SV with NOL increased slightly except that of CoFe FL. NOLs were added at different positions to study the effects of NOL on lambda(s) of CoFe FL. All lambda(s) of CoFe FL change from negative to positive and its absolute value also increases significantly with CoFeOx related NOL added below. Our lambda(s) and surface roughness results indicated that the structure of the film not the roughness dominates lambda(s) of ultrathin FL in SVs. (C) 2006 American Institute of Physics.