Naslov (srp)

Magnetoimpedansni efekat amorfnih žica sa magnetno mekim svojstvima

Autor

Orelj, Jelena, 1985-

Doprinosi

Mitrović, Nebojša, 1962-
Pavlović, Vladimir, 1966-
Surla, Radoslav, 1974-
Nedeljković, Borivoje, 1974-

Opis (srp)

U okviru disertacije su istraživani fenomeni koji pripadaju naučnojoblasti razvoja savremenih senzora na bazi magnetoimpedansnih (MI) elemenatanačinjenih od amorfnih metalnih legura na bazi kobalta i legura na bazi gvožđa(žice sastava Co68.15Fe4.35Si12.5B15, Co72.5Si12.5B15 i Fe73.5Nb3Cu1Si13.5B9). Sve legurepripadaju materijalima sa magnetno mekim svojstvima, što je prvi preduslov zaizraženi MI-efekat (promena impedanse pod uticajem spoljašnjeg jednosmernogmagnetnog polja Hex pri određenim frekvencijama f naizmenične struje kojaprotiče kroz uzorak). Dakle, centralna istraživanja su sprovedena u domenufunkcionalne zavisnosti impedanse Z (Hex, f).Za potpunu analizu MI-efekta pored modula impedanse, detaljno suanalizirane i zavisnosti realnog MR (Hex, f) i imaginarnog dela MX (Hex, f)impedanse. Time je omogućena analiza promene dubine magnetnog prodiranjaδm(Hex, f)korišćenjem eksperimentalnih podataka za magnetootpornost MR (Hex, f),dok je za analizu magnetne permeabilnost μ (Hex, f) neophodno i poznavanjezavisnosti magnetoreaktanse MX (Hex, f).Uporedna istraživanja zavisnosti magnetne dubine prodiranja odfrekvencije i magnetnog polja δm (Hex, f) kod amorfnih žica sastavaCo68.15Fe4.35Si12.5B15i Fe73.5Nb3Cu1Si13.5B9 su pokazala da se kod legure na bazi kobaltadostižu za red veličine niže vrednosti dubine prodiranja i za red veličineviše vrednosti MI-odnosa (nekoliko stotina procenata kod legure na bazikobalta naspram nekoliko desetina procenata kod legure na bazi gvožđa).Optimalne radne frekvencije MI-elemenata su definisane potrebomizbegavanja dominantnog uticaja longitudinalne anizotropije, tj. dinamikemagnećenja domena u unutrašnjosti amorfnih žica, koja značajno smanjujeosetljivost mikromagnetnog senzora. Potrebno je ostvariti dominantan uticajcirkularne anizotropije, tj. mehanizam rotacije vektora magnetizacije udomenima raspoređenim po obodu žice. Najveće vrednosti osetljivosti MIelementa su evidentirane kod amorfnih žica legure Co68.15Fe4.35Si12.5B15 prifrekvencijama 4-5 MHz, a dostignute vrednosti su oko 0,4 %/A/m.

Opis (srp)

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Opis (eng)

The development of advanced sensors based on magnetoimpedance (MI) elementsprepared on cobalt-based (Co68.15Fe4.35Si12.5B15 and Co72.5Si12.5B15) and iron-based(Fe73.5Nb3Cu1Si13.5B9) amorphous alloys was investigated. All investigated alloys are softmagnetic materials, which is the first prerequisite for a pronounced MI effect (impedancechange under the influence of an external DC magnetic field Hex at certain frequencies f ofalternating current flowing through the sample). Thus, the central research in thedissertation is the behavior of the impedance on magnetic field and frequency Z (Hex, f).In addition to the investigation of the MI-effect by MI-modulus Z (Hex, f), a completeanalysis of two crucial MI-parameters: penetration depth δm (Hex, f), and relative magneticpermeability of wire μw (Hex, f) were performed by exploiting all three electrical MIelement components MR (Hex, f), MX (Hex, f), and Z (Hex, f). A theoretical impedance modelfor a cylinder, which includes both magnetoresistance MR and magnetoreactance MX, hasbeen successfully used to estimate the magnetic permeability values μ (Hex, f).Comparative studies of the dependence of the skin depth on the magnetic field andfrequency δm (Hex, f) in amorphous wires of Co68.15Fe4.35Si12.5B15 and Fe73.5Nb3Cu1Si13.5B9alloys have shown that the cobalt-based alloy attains an order of magnitude lower valuesof penetration depth and for an order of magnitude higher MI-ratio (several hundredpercent in cobalt-based alloy vs. several tens of percent in iron-based alloy).The optimal frequencies of MI-elements are selected to avoid the dominantinfluence of longitudinal anisotropy, i.e. dynamics of magnetization of domains in the coreof wires, which significantly reduces the sensitivity of the micromagnetic sensor.Therefore, it is necessary to realize the dominant influence of the skin effect on circularanisotropy, i.e. mechanism of magnetization vector rotation in domains distributed on theshell of the cylinder. In these conditions of strong skin effect, the values of the skin depthare about one-tenth of the wire radius, and the influence of the magnetic field on theincrease of the penetration depth (i.e. on the decrease of the impedance) is pronounced.The highest sensitivity of the MI-elements was recorded with amorphous wires ofCo68.15Fe4.35Si12.5B15 alloy at frequencies of 4-5 MHz, and the attained sensitivity is about0.4 % /A/m.

Jezik

srpski

Datum

2024

Licenca

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