Interface reactions in Ta/Ni 81Fe 19/Ta structures and their influence on magnetic properties

Abstract

Ta/Ni 81Fe 19, Ni 81Fe 19/Ta, Cu/Ni 81Fe 19, and Ni 81Fe 19/Cu structures are commonly used in the magnetic multilayers with giant magnetoresistance. For a Ta/Ni 81Fe 19/Ta fundamental structure, Ta seed and Ta cap layers result in a loss of moment equivalent to a magnetically dead layer of thickness 1.6 ± 0.2 nm. Experimental results show that a chemical reaction between Ta and Ni 81Fe 19 takes place at the Ta/Ni 81Fe 19 and Ni 81Fe 19/Ta interfaces. The thickness of the magnetically dead layer was significantly reduced by the insertion of a small amount of Bi in the Ta/Ni 81Fe 19/Ta structure (i.e. Ta/Bi/Ni 81Fe 19/Ta). This result indicates that Bi acts as a surfactant that can suppress the interface reaction in multilayers. For a Cu/Ni 81Fe 19/Cu film, permalloy layers have hardly lost their magnetic moment since interface reactions at the Cu/Ni 81Fe 19 interface or Ni 81Fe 19/Cu interface hardly occurs.