Domain structure, magnetic properties, and giant magnetoimpedance of FeNi/Ti‐based multilayers

Abstract

Magnetic multilayers consisting of magnetic FeNi and non‐magnetic Ti layers were prepared by rf‐sputtering. Magnetic measurements and magnetic domain structure observations were used for characterization of the samples. The magnetoimpedance performance of FeNi/Ti‐based multilayers is evaluated in terms of the magnitude of the effect and its sensitivity with respect to applied magnetic field. The results show that the trilayer with Ti layer of 6 nm (sample A), deposited to avoid the possibility of appearance of a trascritical state, performs better than the sample with a 10 nm Ti layer (sample B). The best results are obtained with [FeNi/Ti]5/FeNi multilayered structure (sample C) reaching a value of about 60% of variation of the impedance at 180 MHz and a sensitivity of about 22%/Oe at 180 MHz.

Nanostructured Magnetoimpedance Multilayers with Different Thickness of FeNi Components

“…1(b)) for FeNi(25). The well defined two peak shape of the MI curves confirms that the effective magnetic anisotropy is a transverse magnetic anisotropy with low dispersion of local easy magnetization axes [2,[8][9].…”

“…One can see that for a very wide frequency range asymmetric multilayers with the top layer thicker than 100 nm show a higher magnetoimpedance ratio. In previous studies of FeNi/Cu-based symmetric multilayers with FeNi layers of 100 nm they observed that the system reached the highest MI for the thickness of each magnetic multilayer equal or above the thickness of the central Cu-lead [8][9]. This rule does not work for asymmetric structures.…”

“…On the other hand Volchkov et al designed FeNi-based multilayers on the basis of rather thick FeNi layers (of the order of 170 nm) separated by Cu spacers [8]. E. Fernandez et al used FeNi layers of the order of 100 nm separating them by Ti spacers [9]. Although different geometrical parameters like thickness to width ratio were the subject of intensive research, the role of the thickness of the individual layers in the multilayered MI structures is still not systematically investigated.…”

“…It is also worth mentioning that in all previous studies MI multilayers were symmetric, i.e. had the same total thickness of magnetic components on top and at the bottom of the central copper lead [2,[7][8][9][10]. For particular applications such as biosensing or non-destructive testing non-symmetric MI structures can be beneficial.…”

Nanostructured giant magneto-impedance multilayers deposited onto flexible substrates for low pressure sensing

“…Previous studies [ 5 ] have demonstrated that, for FeNi films, once the thickness reaches 200 nm, an out-of-plane magnetization component appears, ruining the in-plane anisotropy and the magnetic softness required for high GMI values. The insertion of 6-nm thick titanium layers between successive 170-nm thick permalloy layers interrupts the developing of the out-of-plane component of the magnetization, allowing to obtain about one micron-thick films without deteriorating the magnetic softness [ 6 ]. It is also possible to increase the GMI performance even at lower frequencies, creating a sandwich structure by inserting a nonmagnetic layer between two magnetic stacks.…”