Elaboration et structuration d'empilements Co/Al2O3/Co/Ni80/Fe20 par pulvérisation ionique
Institution:
Paris 11Disciplines:
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Abstract EN:
A magnetic tunnel junction (mtj) is composed by two thin ferromagnetic layers (cobalt, nickel, iron), separated by a thin insulating barrier (alumina). This structure has evolved since the measurement of the first tunnel magnetoresistance (tmr) at room temperature in 1995. Currently, magnetic tunnel junctions are used in the new generation of magnetic memories (mram) and as read head in hard drives. This study presents the elaboration of cobalt/alumina/cobalt/permalloy magnetic tunnel junctions by ion beam sputtering (ibs). The aim is to prove the potentiality of this deposition technique, which is little used for this application. The tunnel magnetoresistance has been determined by two methods. The first method has required a pattering process of the full stacking in a clean room, in order to elaborate the electric contacts. The second method is based on the cipt principle (current in plane tunneling), which can be performed directly on the full stack. The mrt value has been evaluated at 7,5%. To improve this first result, ion beam sputtering simulations have been performed with srim2003 software. These simulations will lead us to optimize the experimental conditions of the thin films elaboration.
Abstract FR:
Une jonction tunnel magnetique (jtm) est composee de deux couches minces metalliques ferromagnetiques (cobalt, nickel, fer) separees par une barriere isolante ultramince (alumine) dans sa forme la plus simple. Cette structure a evolue depuis la mesure de la premiere magnetoresistance tunnel (mrt) à temperature ambiante en 1995. Actuellement, les jonctions tunnel magnetiques sont utilisees par la nouvelle generation de memoire vive magnetique (mram) et par les tetes de lecture des disques durs. Cette etude presente l'elaboration de jonctions tunnel magnetiques cobalt/alumine/cobalt/permalloy par pulverisation ionique. On veut ainsi demontrer la potentialite de cette technique de depot, qui est peu utilisee dans ce domaine. La mesure de la magnetoresistance tunnel a ete effectuee selon deux methodes. La premiere methode a necessite le developpement d'un procede de structuration realise en salle blanche, afin d'elaborer les contacts electriques necessaires a la mesure. La deuxieme methode repose sur la technique appelee cipt (current in plane tunneling). Cette deuxieme technique presente l'avantage de ne necessiter aucune structure particuliere. Cette derniere methode a permis de mesurer une mrt de 7,5%. Afin d'ameliorer ce premier resultat, des simulations de pulverisation ionique ont ete effectuees a l'aide du logiciel srim2003. Elles permettront à terme, d'optimiser les conditions de depot des couches minces.