Compositional Evolution And Magnetic Properties Of Nanocrystalline Fe 73.5cu1nb3si13.5b9

Melt-spun FeCuNbSiB ribbons were annealed at 540-550°C for various times (≤1 h). The development of a nanocrystalline structure was investigated by means of Mössbauer spectroscopy. From measured hyperfine fields and intensities the crystalline phase was inferred to be pure Fe 1-xSix, with x=0.18 after 1 h annealing. The residual amorphous volume fraction was determined to be ≅50%. With help of these results it has been possible to evaluate the amorphous contribution to magnetostriction in the nanocrystalline state. The development of a nanocrystalline structure was found to play a role in the main mechanisms of magnetic disaccommodation.711260086012Elfusa,Mineracao Jundu,Netzsc

The Influence Of Quenching Rate On Magnetic Properties Of Amorphous Ribbons

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Five sets of amorphous ribbons of the composition Fe73.5Cu 1Nb3Si13.5B9 produced with different quenching rates (QR) were studied in order to verify the influence of the topological disorder on magnetic properties. For this purpose several magnetic methods were applied. Significant differences have been found between the results of magnetic disaccommodation He·Δμ/μ, pinning field Hp and stress dependence of the magnetic permeability μ/μ0(σ) of as-cast materials produced at different QR. The values of He·Δμ/μ and Hp are directly proportional to the disorder degree of the samples. The μ/μ0(σ) curves display broad maxima, which are found to be related to the quenched-in stresses. In contrast with these results, no significant effects of the amorphous structure on the Curie temperature and Mössbauer spectra were found, because other parameters are dominating.7310660366052011/01071-3; FAPESP; São Paulo Research FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

MAGNETIC AFTEREFFECTS IN A COBALT ALUMINOSILICATE SPIN GLASS

On présente des mesures de susceptibilité statique d'un verre alumino-silicate contenant 35,5 % at. de Co, à des températures proches de celle (~ 7,8 K) où la susceptibilité en champ alternatif présente un pic. Aucune anomalie n'a été observée à cette température. Des effets de rémanence apparaissent en-dessous de 7 K. On discute ces résultats en termes du modèle à domaines superparamagnétiques.Low-field DC susceptibility measurements on a 35.5 at.% Co aluminosilicate glass, at temperatures around the AC susceptibility peak temperature (~ 7.8 K), are reported. No anomaly is found at that temperature. Remanence effects are apparent below 7 K. The results will be discussed in terms of the superparamagnetic domain model