Influence of Cobalt Substitution on Hyperfine Interactions in (Fe1−xCox)76Mo8Cu1B15(Fe_{1-x}Co_x)_{76}Mo_8Cu_1B_{15} Alloys

The effect of cobalt substitution on structure, magnetic behaviour, magnetic arrangement, and hyperfine interactions in $(Fe_{1-x}Co_x)_{76}Mo_8Cu_1B_{15}$ (x = 0, 0.1, 0.2, 0.25, 0.5) is studied by the Mössbauer spectrometry for both as-quenched and annealed alloys. Partial substitution of Fe by Co resulted in an enhancement of the average value of hyperfine magnetic field distributions as a function of x probably due to higher magnetic moment of Co. After annealing, a two-phase nanocrystalline structure composed of amorphous matrix and bcc-FeCo nanocrystallites was observed. Mössbauer spectra were fitted with up to four six-line patterns of narrow lines assigned to different number of Co nearest neighbours inside a bcc-FeCo lattice

Thermal Expansion of Free-Volume in Hexadecane Confined in the Silica Gel Nanopores

Temperature dependence of the free-volume of voids in hexadecane (HXD) confined in the 3 nm silica gel pores (Develosil-30) was measured by positron annihilation lifetime spectroscopy. Different amount of HXD was filled into the pores of matrix. The anomalous thermal expansion was observed in the partially filled pores with extremely low filling. The thermal expansion coefficient of free-volume voids in this solidified HXD layer has a negative sign at temperatures below 180 K compared to high- or full-filled pores of silica gel. At these temperatures, the positron annihilation lifetime spectroscopy measurements demonstrate the appearance of a new type of the free volume within HXD which has been interpreted as the cracks in the HXD layer on the inner walls of matrix cavities. The differential scanning calorimetry method confirmed that the processes were enacted within pores and not on the outer surfaces of silica gel grains. In the sample with the extremely low filling, only the one HXD solidification/melting effect connected with confined states is manifested

Unusual magnetic anisotropy of Si-poor FeNbCuBSi alloys

If compared to ribbons of standard FeNbCuBSi (13÷16.5 at.% Si) nanocrystalline alloy, different annealing behaviour is displayed if the above alloy contains 10 and less at.% of Si. The most striking difference is observed on samples annealed/nanocrystallized in an atmosphere (e.g. Ar), where the hard direction is aligned along the ribbon's long axis. The particular annealing behaviour of magnetic anisotropy varies with Si contents, with annealing time and yet it differs for vacuum annealing. These peculiarities are studied on a series of Si-poor FeNbCuBSi alloys by magnetic measurements and Mössbauer spectroscopy, consulting DSC and density measurements as well. Some of the abundant problems are discussed in detail in this work. The main idea to explain the behaviour is based on a squeezing-surface effect which results in forming of magnetoelastic as well as of stress induced anisotropy

Magnetostrictive behaviour of Fe73.5Si13.5B9Nb3-xMoxCu1 alloys

Magnetostriction, dilatation and calorimetric measurements were performed on FINEMET type as-quenched and heat treated ribbons. Nb was gradually replaced by Mo in order to study the influence of the refractory elements exchange on several magnetostriction parameters. The results could be correlated with magnetic and structural transformations throughout thermal treatments and assured that the whole series is suitable for technical applications.Fil: Silveyra, Josefina María. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; ArgentinaFil: Cremaschi, Victoria Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; Argentina. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; ArgentinaFil: Vlasák, G.. Slovak Academy of Sciences; EslovaquiaFil: Illeková, E.. Slovak Academy of Sciences; EslovaquiaFil: Janičkovič, D.. Slovak Academy of Sciences; EslovaquiaFil: Švec, P.r. Slovak Academy of Sciences; Eslovaqui