Banca de DEFESA: GUSTAVO HENRIQUE BASTOS DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GUSTAVO HENRIQUE BASTOS DA SILVA
DATE: 30/03/2022
TIME: 10:00
LOCAL: PGMTR
TITLE:

MAGNETOIMPEDANCE IN MAGNETIC MULTILAYERS DEPOSITED ON SILICON

KEY WORDS:

Magneto-impedance, Magnetic Sensors, Multilayers, Thin Films.

PAGES: 94
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

We present a study of the magnetoimpedance (MI) measured in multilayer elements prepared by optical photolithography and by the sputtering deposition technique. Nanostructures are composed of layers of [Py (100 nm) / Ti (6 nm)]4 / Cu (400 nm) / [Py (100 nm) / Ti (6 nm)]4 deposited on silicon (Si), where Py (permalloy) is a magnetic alloy with composition Ni₈₁Fe₁₉ and Ti and Cu represent, respectively, metallic layers of titanium and copper. Nanostructures were made in “ribbon” geometry, a meander with two segments in the form of “U”, as well as meanders with 12 segments, one with “rectangular” vertices and another with “rounded” vertices. Hysteresis loops were obtained at room temperature (T = 298K) using a VSM type vibrating sample magnetometer (Vibrating Sample Magnetometer). The diamagnetic contribution of Si obtained, thus allowing to obtain the magnetization and magnetization of the multilayers. Values were obtained for the coercive field H_c of about 5 Oe which is typical of ferromagnetically soft alloys. Measurements of electrical impedance (Z) were also made at room temperature. The magnetic field is swept in the range of ± 4.0 kOe in both the longitudinal and transverse configurations of the samples plane. The amplitude of the Iac current was kept constant (= 2 mA) while the frequency f of the electrical current was swept from 100 kHz to 30 MHz. The MI data showed two distinct regimes. Below 5 MHz the dependence o Z with f is strongly influenced by the magnetic nanostructure and by the substrate, while above 15 MHz a resonance is observed associated with the transmission line composed of the coaxial cables, connectors and twisted pairs used. Values in the range of 5 – 40 mΩ were obtained for the maximum variation of Z relative to the value measured at 4.0 kOe whose value depends on the geometry of the nanostructure. MI was also investigated in a structure with a ribbon geometry deposited on glass in order to confirm the influence of the Si substrate and to make a comparison with data previously measured in a similar nanostructure. MI was also investigated in a structure with a ribbon geometry deposited on glass in order to confirm the influence of the Si substrate and to make a comparison with data previously measured in a similar nanostructure. For this sample, ΔZ values were much higher (~ 600 mΩ) than in the one deposited in Si (~ 40 mΩ). It is also important to note that for samples deposited on silicon there is a strong dependence of Z with f in the range from 100 kHz to 10 MHz. The dc resistance values for samples deposited on silicon were: 8.1 Ω (tape), 6.8 Ω (2-dash), 20.1 Ω (square-edged meander) and 45.2 Ω (round-edged meander). For the sample on glass, the electrical resistance was 3.2 Ω. The contribution of the Si substrate was calculated using a CPE (Constant Phase Element) model, while for the resonance associated with the transmission line, an RLC-type resonant circuit was used. Finally, the GMI results were interpreted using the model developed for planar structures with semi-infinite geometry.

BANKING MEMBERS:
Interno - 2457389 - EDUARDO PADRON HERNANDEZ
Presidente - 1133626 - FERNANDO LUIS DE ARAUJO MACHADO
Externo à Instituição - JOAO MARIA SOARES - UERN