Giant magnetic impedance of film nanostructures adapted for biodetection

A comparative study of the magnetic properties and giant magnetic impedance of Fe₁₉Ni₈₁/Su/Fe₁₉Ni₈₁ film structures fabricated by the method of ion-plasma evaporation is performed versus the geometry of an impedance element. The geometrical parameters of the Fe₁₉Ni₈₁/Сu/Fe₁₉Ni₈₁ structures are estimated from the viewpoint of obtaining strong magnetic impedance effect and possible application of these structures for detection of bioelements with magnetic markers. Widening of the structures necessary for increasing their active surface area weakens the magnetic impedance effect, and the length increase is limited by the optimal working biodetector frequencies and electromagnetic wave propagation processes.     

Impedance and magnetic properties of CoFeCrSiB amorphous ribbons near the curie point

The influence of temperature on the magnetic properties and magnetoimpedance of Co₆₄Fe₃Cr₃Si₁₅B₁₅ and Co₆₇FCr₃Si₁₅B₁₂ amorphous ribbons having different Curie points are studied. The impedance and its component are found to change greatly when the ribbons pass into the paramagnetic state. This finding can be used to determine the Curie point of ferromagnets and design high-sensitivity thermal transducers.     

The Magnetocaloric Effect in the Vicinity of the Magnetic Compensation Temperature of Amorphous Gd–Co Ferrimagnetic Films

Physics of the Solid State - The results of the study of the magnetic and magnetocaloric properties of amorphous Gd–Co ferrimagnetic films possessing perpendicular magnetic anisotropy in a...     

Low field microwave absorption and magnetization process in CoFeNi electroplated wires

Ferromagnetic resonance （FMR）, Ferromagnetic antirresonance （FMAR） and low field magnetoimpedance （MI） are the characteristic features of high frequency losses in applied fields. While some results on FMR and FMAR in CoFeNi electroplated wires were reported earlier, here we present microwave absorption in CuBe wires electroplated by 1 μm FeCoNi magnetic layer at very low fields. These data are comparatively analysed together with longitudinal hysteresis loops in order to reveal the correlation between power absorption and magnetization processes. Microwave studies are made by using the cavity perturbation method at 9.65 GHz for a DC field parallel to the sample axis, and with microwave magnetic field hrf parallel or perpendicular to the wire axis. Two peaks have been observed in all samples, one is due to FMR, and the other is, at very low fields, related to MI. The MI peaks represent minima in power absorption. By comparing with the hysteresis loop we remark the close correspondence between the MI phenomena in the axial mode and the concomitant magnetization process.     

Peculiarities of the Giant Magnetoimpedance in Permalloy-Based Film Structures in the Important Temperature Range for Practical Applications

Multilayer structures based on Fe19Ni81 films have been obtained by ion-plasma sputtering and investigated on an impedance spectroscopy apparatus equipped with a temperature unit. An increase in the magnetoimpedance ratios for the total impedance and its real part has been found for the multilayer structure (Cu/FeNi)₅/Cu/(Cu/FeNi)₅ upon heating from 25 to 50°C. The maximum of the giant magnetoimpedance ratio of the total impedance ΔZ/Z = 56% has been observed at a frequency of 80 MHz with a sensitivity of 18%/Oe, while the maximum of the real part ΔR/R = 170% was observed at the frequency of 10 MHz with the sensitivity of 46%/Oe. Magnetization and resistivity at the direct current have been found to depend insignificantly on the temperature and, hence, the relaxation mechanism due to the magnetoelastic anisotropy was proposed as the most probable mechanism of increasing the value and sensitivity of the magnetoimpedance effect.     

Giant magnetoimpedance for biosensing: Advantages and shortcomings

Biosensors are an important area of modern sensor applications. Magnetoimpedance (MI) phenomenon was proposed for biosensing in 2003. Since that MI biosensor prototypes based on amorphous ribbons, multilayered structures, amorphous rapidly quenched wires and glass covered microwires were designed and tested. In this paper the advantages and shortcomings of MI-based devices for magnetic labels or label-free biodetection are discussed in view of recent results.     

Ferrimagnetic properties of Co/(Gd–Co) multilayers

Co/(Gd–Co) multilayers have been prepared by rf-sputtering and investigated by means of Transverse Magnetooptic Kerr Effect (TMOKE), SQUID and VSM magnetometry. The composition of amorphous _Gd0.36Co0.64${\mathrm{Gd}}_{0.36}{\mathrm{Co}}_{0.64}$ layers was chosen so that their saturation magnetization was dominated by Gd moments in all the temperature range. Co and Gd–Co layers formed a macroscopic ferrimagnetically coupled system displaying a compensation temperature. Complete magnetic moment compensation was found at such point. An inversion of TMOKE hysteresis loops and a divergent behaviour of coercivity were also observed. By changing the layers thickness it has been possible to control the magnetic characteristics of the Co/(Gd–Co) structures, in particular the compensation takes place at different temperatures.     

Non-linear giant magnetoimpedance

Very high and sensitive magnetoimpedance effect has been studied in FeCoNi magnetic tubes electroplated onto CuBe wire for the frequency of 1 MHz order. Strong non-linear effects have been observed. The high harmonics generation was investigated. The harmonics show larger variations with the external field than the fundamental frequency. This super high sensitivity of the harmonics is promising for applications.