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APSTRAKT: U ovoj disertaciji su prikazani rezultati ispitivanja legure Fe72Cu1V4Si15B8, koja pripada familiji FINEMET-tipa legura. Legura je izrađena ultrabrzim hlađenjem rastopa legure na rotirajućem disku. Dobijena legura ima već formirane nanokristalne faze (α-Fe(Si) i Fe23B6 faze), koje se nalaze u amorfnoj matrici, što je ustanovljeno XRD analizom i Mesbauerovom spektroskopijom. Pored toga, Mesbauerovom spektroskopijom je ustanovljeno postojanje znatno više kristalnih faza koje zbog male zastupljenosti nisu detektovane XRD analizom. Legura je termički tretirana, što je indukovalo strukturne promene koje su doprinele promeni magnetnih svojstava. DTA analizom je legura zagrevana do 1073 K, različitim brzinama (β= 5K/min, 10K/min i 20 K/min), kojom su ustanovljena dva kristalizaciona pika: (i) od 750 K do 780 K i (ii) od 875 K do 900 K (za β= 5 K/min). Oba pika su nesimetrična, što ukazuje na složenost procesa kristalizacije. Ovi pikovi odgovaraju jednom termomagnetnom piku u intervalu od 745 K do 875 K (za H=7960 A/m i β= 4 K/min). Termomagnetnim merenjima je ustanovljena Kirijeva temperatura amorfne faze legure koja iznosi oko 615 K i Kirijeva temperatura iskristalisane legure koja iznosi oko 875 K. Nakon toga su uzorci oblika trake odgrevani različitim temperaturama (Tan= 573 K – 973 K). Ustanovljeno je da je pri Tan= 773 K došlo do najvećeg povećanja magnetizacije zasićenja, Ms uz minimalno povećanje koercitivnog polja, Hc. Povećanje Ms se objašnjava uvećanjem zastupljenosti α-Fe(Si) faze, sa porastom Tan, usled transformacije amorfne u kristalnu fazu. Prosečna veličina novoformiranih kristalita α-Fe(Si) faze ista je kao i veličini kristalita u neodgrevanoj leguri do Tan=773 K. Pri Tan>773 K dolazi do naglog povećavanja prosečne veličine kristalita ove faze, što uzrokuje slabiju pokretljivost magnetnih domena, zbog čega se smanjuje Ms. Isti trend promena Ms uočen je i za longitudinalnu i normalnu (perpendikularnu) orijentaciju uzorka u magnetnom polju u odnosu na temperaturu odgrevanja. Konstantan porast Hc sa porastom Tan, povezano je sa boridnim fazama gvožđa, čiji se udeo sa odgrevanjem takođe povećava. Naime, odgrevanjem se metastabilna faza Fe23B6 transformiše u stabilnu Fe2B fazu, a proces se završava na Tan= 723 K. Nemagnetni atomi bora (B) koji okružuju α-Fe smanjuju izmensku interakciju atoma Fe, što je razlog degradacije magnetno mekih svojstva. Odgrevane trake su analizirane i Mesbauerovom spektroskopijom, gde su rezultati pokazali da ni jedan od podspektara u potpunosti ne odgovara identifikovanim fazama Fe23B6 i Fe2B. Ovo se objašnjava rastvorljivošću elemenata Si i V u kristalnoj rešetki Fe, kao i bliskog atomskog faktora rasejanja atoma Fe i V, pa se pretpostavlja da u kristalnim rešetkama ovih faza ima u manjoj meri ugrađenih atoma V i Si. Pored toga na osnovu podspektara koji korespondiraju Fe(Si) fazi, pretpostavlja se da u pojedinim delovima ove faze ima različitog rasporeda prvih suseda atoma Fe, kao i ugrađenog V, što ukazuje na postojanje i drugih oblika kristalnih rešetki ove faze. Ove pretpostavke su potvrđene skenirajućim elektronskim mikroskopom gde su EDS analizom detektovana određena zrna bogata vanadijumom. Takođe, ovom metodom pronađena su i mesta bogata bakrom, što sugeriše na postojanje klastera atoma bakra koji se prvi izdvajaju prilikom kristalizacije FINEMET sistema i isti pospešuju nukleaciju α-Fe(Si) faze... ABSTRACT: This dissertation presents the results of examination of the alloy Fe72Cu1V4Si15B8, which belongs to the FINEMET-type family of alloys. The alloy was prepared with a rapid quenching of the melt on a rotating disc. The as-prepared alloy already contains nanocrystals of α-Fe(Si) and Fe23B6 phases, in an amorphous matrix, that is observed by XRD analysis and by Mössbauer spectroscopy. In addition, Mössbauer spectroscopy revealed the existence of significantly more crystal phases that, due to their low presence, were not detected by XRD analysis. The alloy was thermally treated, which induced structural changes that contributed to the changes in magnetic properties. First, the alloy was heated to 1073 K, at different rates (β = 5K/min, 10K/min and 20 K/min), and two crystallization peaks were found by DTA analysis: (i) from 750 K to 780 K, and (ii) from 875 K to 900 K (for β = 5 K/min). Both peaks are asymmetric, which indicates the complexity of the crystallization process. These peaks correspond to a single thermomagnetic peak in the range from 745 K to 875 K (for H = 7960 A/ m and β = 4 K/ min). Thermomagnetic measurements revealed the Curie temperature of the amorphous phase of the alloy at 615 K, and the Curie temperature of the crystallized alloy at 875 K. After that, the ribbon-shaped samples were annealed at different temperatures (Tan = 573 K - 973 K). It was found that at Tan = 773 K there was the huge increase in saturation magnetization (Ms) with a minimal increase in the coercive field (Hc). The increase in Ms is explained by the increase of the abundance of α-Fe (Si) phase, with the increase of Tan, due to the transformation of amorphous into crystalline phase. The average size of the evolved crystallites of α-Fe (Si) phase is the same as the size of crystallites in the as-prepared alloy up to Tan = 773 K. At Tan > 773 K there is a sharp increase in the average size of crystallites of this phase, which causes slow mobility of magnetic domains due to reduced width of the domain walls, that is why the Ms decreases. The same trend of changes in Ms was observed for both longitudinal and perpendicular orientation of the sample in the magnetic field with increase of the annealing temperature. The constant increase of Hc with the increase of Tan is connected with the boride phases of iron, whose weight fraction also increases with the annealing. By annealing, the metastable phase Fe23B6 is transformed into a stable Fe2B phase, and the process ends at Tan = 723 K. Nonmagnetic boron atoms (B) surrounding α-Fe reduce the exchange interaction of Fe atoms, and consequently, the degradation of magnetically soft properties occurs. The annealed ribbons were also analysed by Mössbauer spectroscopy, where the results showed that none of the sub-spectra fully corresponded to the identified Fe23B6 and Fe2B phases. This is explained by the solubility of the elements Si and V in the crystal lattice of Fe, as well as by the similar atomic scattering factor of Fe and V atoms. It is assumed that some of V and Si atoms are embedded in the crystalline lattices of these phases. In addition, based on the subspectra corresponding to the Fe (Si) phase, it is assumed that in some parts of this phase there is a different arrangement of the first neighbors of the Fe atom, as well as a built-in V, which indicates the existence of other crystalline forms of this phase. These assumptions were confirmed by scanning electron microscopy where certain vanadium-rich grains were detected by EDS analysis. Also, with this method, copper-rich sites were found, which suggests the existence of clusters of copper atoms that are formed at the onset of crystallization of the FINEMET system and they accelerate the nucleation of the α-Fe (Si) phase...