Changes in magnetic and magnetoresistive characteristics of Ni–Fe/Au/Co/Au multilayers induced by annealing

Abstract

PACS 75.47. De, 75.70.Cn In this contribution the influence of annealing on magnetization reversal and on the giant magnetoresistance effect of [Ni 80 Fe 20 /Au(t Au )/Co(t Co )/Au(t Au )] 10 multilayers with t Co = 0.6, 0.8 nm and t Au = 1.5, 2.2 nm was studied. Measurements performed for as-deposited samples and after subsequent annealing at T a (423 K < T a < 523 K) show that the GMR effect is stable under annealing below 475 K. It even slightly increases, for T a above 450 K, opening a path for a GMR value control and therefore is important for applications. The most pronounced changes were observed in the saturation field Co SH which is a measure of perpendicular anisotropy. The significant variations were also noticed in the central part of the M(H) and R(H) curves. They are characterized by the nucleation field H N and the saturation field H S⊥ which are related to the appearance and disappearance of stripe domains in Co layers, respectively. The influence of T a on values of Co S H , H S⊥ and H N will be discussed.

Stability of perpendicular anisotropy in NiFe/Au/Co/Au multilayers

“…As was already shown [3] the MR amplitude in NiFe/Au/ Co/Au MLs is not changed by annealings at T A ≤ 250 • C. Annealings at higher temperatures (T A = 300 • C) lead to a strong degradation of the MR effect (Fig. 1).…”

“…In particular, it was demonstrated that [NiFe/Au/Co/Au] N multilayers display giant magnetoresistance (GMR) [1] and that their magnetic and magnetoresistive properties can be modified in a broad range by adjusting layers thicknesses [1] and/or using composite magnetic layers [2]. It was also shown that they are resistant to low temperature annealings [3] and display satisfactory temperature stability [4]. The aim of this study is to explain the observed changes of magnetic properties of [NiFe/Au/Co/Au] 10 MLs under the influence of high temperature annealings and to determine Co thickness range assuring the high thermal stability.…”

“…Magnetic layered structures with alternating in-plane and outof-plane anisotropy in neighboring magnetic layers, separated by nonmagnetic spacer, were shown to possess properties interesting from an application point of view [1][2][3][4][5]. In particular, it was demonstrated that [NiFe/Au/Co/Au] N multilayers display giant magnetoresistance (GMR) [1] and that their magnetic and magnetoresistive properties can be modified in a broad range by adjusting layers thicknesses [1] and/or using composite magnetic layers [2].…”

Selective Modification of Magnetic Properties of Co1/Au/Co2/Au Multilayers by He Ion Bombardment

“…For the field applied perpendicularly this leads to the GMR-like resistance changes caused by a creation and an annihilation of domains (see the left inset of Fig. 2b) [12]. It is important to note that the character of the R(H) dependences underwent dramatic changes (GMR amplitude changes are irrelevant to our argumentation).…”

“…It is important to note that the character of the R(H) dependences underwent dramatic changes (GMR amplitude changes are irrelevant to our argumentation). Concentrating on the perpendicular configuration, it can be seen that R(H) dependence characteristic of layers with perpendicular anisotropy and the dense domain structure is transformed into the dependence observed for MLs with alternating in-plane and out-of-plane anisotropies in successive layers [12][13][14]. Summing up, the resistance measurements confirm the observation inferred from the M (H) measurements, namely that the IB led to the switching of the EA direction in the 1 nm thick Co layers (see Fig.…”