Magnetic structure ofNi-richNi1−xTax

Abstract

Tantalum is used in magnetic devices as a buffer layer. However, Ta has deleterious effects on the magnetic properties. We study the magnetic structure of Ni-rich Ni 1−x Ta x alloys using the Korrianga-Kohn-Rostoker Coherent-potential approximation ͑KKR-CPA͒ method. We show that the average magnetic moment vanishes at ϳ12%Ta. The magnetism is shown to be Stoner-like. We also study the magnetic structure of Ta impurities embedded in pure Ni using supercell models. We find that the impurity atom suppresses the moment on neighboring Ni atoms. Finally, we study the effects of Ta additions on moment formation in permalloy ͑Ni 0.8 Fe 0.2 solid solutions͒ using the KKR-CPA method. It is shown that the average moment vanishes at ϳ45% Ta. The effects of Ta on the local moments are also investigated. These calculations are performed using the order-N locally self-consistent multiple-scattering method.

Thermally robust Mo/CoFeB/MgO trilayers with strong perpendicular magnetic anisotropy

“…Overall, the perpendicularly magnetized Ta/CoFeB/MgO films are rather unstable against annealing. It should be pointed out that, Ta interdiffusion has been demonstrated in magnetic multilayer films after heat treatment, which not only degrades MTJs, but also causes significant moment loss and PMA deterioration, especially for the perpendicularly magnetized Ta/CoFeB/MgO films with a very thin CoFeB layer27282930.…”

Controlled enhancement or suppression of exchange biasing using impurityδlayers

“…It should be noted in systems where Ta is placed for example next to permalloy (Ni 81 Fe 19 ), that a chemical reaction takes place between the two layers giving rise to a dead layer. This has an effect of reducing the moment 43,44,45 of the layer. The Pt dusting however, also exhibits an additional feature where H e increases by ∼ 10% above that for the control sample for a δ-dusting < 1.5Å, before then gradually decreasing towards zero.…”

“…It should be noted in systems where Ta is placed for example next to permalloy (Ni 81 Fe 19 ), that a chemical reaction takes place between the two layers giving rise to a dead layer. This has an effect of reducing the moment 43,44,45 of the layer.…”

Effective Band Structure of Random Alloys

“…In metal alloys, the charge on a particular A atom will depend critically if it is coordinated locally mostly by like A atoms or by unlike B atoms [8]. Considering the existence of polymorphous configurations [9][10][11] with attendant loss of periodicity in random alloys, one will be inclined to accept that such alloys do not have energy bands, thus rejecting the wave vector and the band structure as viable concepts. This view represents a departure from the historic tradition of replacing for the polymorphous picture by a repetition of a single or two motifs, as in the virtual crystal approximation [3] the band anticrossing model [12], or the coherent potential approximation [3,13].…”