Effect of induced anisotropy on magnetoimpedance characteristics in NiFe∕Au∕NiFe sandwich thin films

Abstract

The high frequency magnetoimpedance (MI) has been measured in NiFe∕Au∕NiFe narrow sandwich thin films with transverse, longitudinal, and crossed magnetic anisotropies over a frequency range of 50–500MHz. The MI elements have an opened structure with lengths of 2 or 5 mm, widths of 50–200μm and a total film thickness of 1.5μm. The magnetoimpedance characteristics with different field curve shapes, including asymmetrical, have been realized for certain magnetic anisotropy using a dc bias current. Initially the different MI field characteristics have been demonstrated in ferromagnetic microwires with circumferential, helical, and longitudinal anisotropies. Here we have reintroduced these field characteristics for the MI sandwich thin film elements. In an attempt to induce a particular anisotropy in the films the magnetic layers were rf sputtered in the presence of a strong magnetic field, with a further thermal restress treatment of the final MI elements. The use of thin film technology for MI is preferable in many applications because of its compatibility with integrated circuit technology which enables miniaturization, avoiding alignment issues, and wire soldering.

Mirroring the dynamic magnetic behavior of magnetostrictive Co/(Ag,Cu,Ta) multilayers grown onto rigid and flexible substrates

“…For all multilayers, the Z curves reflect the perpendicular alignment of the easy magnetization axis with the ac current and dc magnetic field applied during the MI experiment, a fact already verified in several studies [10,20,21,26,27].…”

Annealing temperature dependance of magnetic properties and magneto-impedance effect in CoZrB alloys

“…The decline of the MI response in the annealed ribbon is attributed to the deterioration of the soft magnetic properties caused by the change of microstructure of the sample with thermal treatments. After Co 72 Zr 8 B 20 being annealed at 540 • C, when coercivity increases with annealing temperature, the wall movements do not occur and the MI effect is due to the magnetization rotation with two symmetrical peaks for a transverse anisotropy [18,19]. According to previous studies [26][27][28], the manipulation of the magnetic anisotropy of the ribbon increases the magnitude of the effect.…”

“…In general, there are two types of MI curves, one is single-peak curve, the other is the double-peak curve. A single-peak curve typically is a characteristic of the longitudinal anisotropy, however, for lower frequencies at appropriate ac current magnitude it can be seen in systems with a transverse anisotropy due to domain wall movements [18,19]. In the present work, the MI curve for the as-quenched Co 72 Zr 8 B 20 alloy belongs to this case.…”

Giant magnetoimpedance effect in sputtered single layered NiFe film and meander NiFe/Cu/NiFe film

“…Particularly, sensors based on the giant magnetoimpedance (GMI) effect have provided a much better alternative because of its high sensitivity, stability and small size. Much effort has been made to investigate the influence of sample structure, such as multilayer [1][2][3][4][5][6][7][8][9] and meandered structure [10][11][12][13][14] of thin films and ribbons, on GMI effect in soft magnetic material. These results suggest that except for the choosing of different materials (wire, thin film and ribbon) and the optimizing treatment (annealing, doping, etc.)…”