Synthesis of giant magnetoresistive multilayers

Giant magnetoresistance (GMR) effect has been discovered in vapor deposited multilayers consisting of alternating layers of ferromagnetic (FM) and nonferromagnetic (NFM) metals. It has become clear that the magnetotransport properties of GMR multilayers are significantly effected by the atomic scale structure of the interfaces between the NFM conducting and FM metal layers.; A combination of experimental and modeling studies have been used to investigate interface structures created during the growth of metal multilayers by RF diode deposition. The consequences of changes to this structure upon magnetotransport properties have also been assessed. The experiments explored the dependence of the magnetotransport properties of Ni₆₅Fe ₁₅Co₂₀/Co₉₅Fe₅/Cu₈₀Ag ₁₅Au₅/Co₉₅Fe₅/Ni₆₅Fe ₁₅Co₂₀ multilayers upon the growth conditions (background pressure, input power). These experimental studies reveal the existence of intermediate background pressure (20mTorr) and plasma power (175W) that result in the highest magnetoresistance. Using a combination of modeling methods, the deposition process conditions have been linked to the energy of the atomic and ion fluxes incident upon the sample surface.; It is well known that the activation barriers impeding atomic assembly are sensitive to local chemical composition and configuration. Experiments revealed that RF diode deposited multilayers utilizing Cu₈₀Ag ₁₅Au₅ as the NFM conducting layer posses significantly superior giant magnetoresistance to otherwise identical device architectures that used pure copper as the NFM conducting layer. The surface roughness of the Cu ₈₀Ag₁₅Au₅ layers was found to be much less than that of pure copper, and the alloying eliminated the formation of pinholes. The atomic scale mechanism responsible for silver's surface flattening effect have been explored. It has been found that silver, when present at a step edge, reduces the Ehrlich-Schwoebel barrier for copper and therefore promotes a step-flow growth mode. Gold is also found to reduce the Ehrlich-Schwoebel barrier, but its potency is less than that of silver due to its lower surface concentration.