Interface reaction of Ta/Ni81Fe19 or Ni81Fe19/Ta and its suppression

Abstract

Ta / Ni 81 Fe 19 and Ni81Fe19/Ta structures are commonly used in the magnetic multilayers with giant magnetoresistance. For a Ta/Ni81Fe19/Ta fundamental structure, Ta seed and Ta cap layers resulted in a loss of moment equivalent to a magnetically dead layer of thickness 1.6±0.2 nm. In order to find out the reason, the composition and chemical states at the interface regions of Ta/Ni81Fe19 and Ni81Fe19/Ta were studied using the x-ray photoelectron spectroscopy and peak decomposition technique. The results show that there are thermodynamically favorable reactions at the Ta/Ni81Fe19 and Ni81Fe19/Ta interfaces: 2Ta+Ni=NiTa2. However, the thickness of a magnetically dead layer was significantly reduced by the insertion of a small amount of Bi in the Ta/Ni81Fe19/Ta structure. This result indicates that a surfactant Bi can suppress the interface reaction in multilayers.

Ultrathin high anisotropic magnetoresistance Ni0.81Fe0.19 films

“…Our XPS result shows that there is no detectable chemical shift and deformation of the spectral shape for Cr, indicating no chemical reaction happening at the interface of the (Ni 0.81 Fe 0.19 ) 0.63 Cr 0.37 (5.5 nm)/Ni 0.81 Fe 0.19 (3.0 nm) film. That is unlike the case of the traditional Ta underlayer, where Ta can readily react with Ni 0.81 Fe 0.19 film at the interface, leading to the decrease of the actual thickness of the Ni 0.81 Fe 0.19 film [15]. Figure 6 shows the total magnetic moment of (Ni 0.81 Fe 0.19 ) 0.63 Cr 0.37 (5.5 nm)/Ni 0.81 Fe 0.19 (y nm) film as a function of the thickness y.…”

“…For permalloy films, Ta is often used as an underlayer that can promote Ni 0.81 Fe 0.19 films to form a good (111) texture [14], resulting in a high AMR value. However, our recent research results [15] show that there is a thermodynamic reaction at the interfaces of Ta/Ni [16,17].…”

Orbit-Engineered Anisotropic Magnetoresistive Effect for Constructing a Magnetic Sensor with Ultrahigh Sensitivity

“…In this regard, extensive studies have been carried out from the perspective of a crystal structure or electron scattering path modulation. For example, a suitable buffer layer (Ta or NiFeCr) or annealing treatment can promote the (111) texture and grain growth of permalloy (NiFe) films, which reduces the electron scattering originating from grain boundaries to improve the AMR ratio effectively. − In addition, the introduction of the specular reflection effect of an adjacent oxide layer can increase the mean free path of conduction electrons in the NiFe layer, which in turn significantly improves the AMR ratio. , Generally, these traditional studies enhanced the AMR effect mainly by modulating the lattice or charge degree of freedom, which leads to a general AMR ratio lower than 4%.…”

The influence of an MgO nanolayer on the planar Hall effect in NiFe films

“…In the Ta/NiFe/Ta film, the interface reaction and the interface diffusion exist at the bottom and top interfaces, which reduce the effective thickness of the NiFe film. 18 In addition, the shunt current in the Ta layer also lowers the sensitivity for sample I. For sample II (i.e., MgO/NiFe/MgO structure), both the interface diffusion and shunt effect were avoided, leading to the increased sensitivity.…”

“…The smooth oxide/metal interfaces play a significant role on the scattering of spin polarized electrons compared to Ta/NiFe/Ta and lead to a large resistivity change as well as a high PHE voltage. 18 Meanwhile, the NiFe grains of sample III formed with better (111) texture and the larger columnar grains after annealing in Fig. 5(c).…”