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Your search keyword '"Ardisson, J.D."' showing total 145 results
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145 results on '"Ardisson, J.D."'

46. 57Fe Mossbauer investigation of R2(Fe1-xCox)17Ny (R=rare earth, x less than or equal to 0.4, y less than or equal to 2.2)

Author

Ardisson, J.D., Boge, M., Persiano, A.I.C., Colucci, C.C., and Gama, S.

Subjects
Mossbauer effect -- Usage, Magnetic fields -- Research, Magnetic alloys -- Research, Intermetallic compounds -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The effects of different contents of nitrogen in both Pr2Fe17 and Nd2Fe17 and of cobalt in both Nd2Fe17 and Nd2Fe17N2 center dot 2 are investigated by means of Mossbauer spectroscopy (MS) and thermal magnetic analysis (TMA). The results confirm that either nitrogen or cobalt increases the hyperfine field (Bhf) as well as the Curie temperature (Tc) of the material. The hyperfine parameters for nominal contents of nitrogen above y = 1.5 are the same as those observed in fully nitrided samples. Our data also reveal that the combination of both N and Co produces an additional increase of Tc. The same behaviour is observed in Bhf of Nd2(Fe1-xCox)17N2 center dot 2 in the range 0 < x < 0.1. After a restricted maximum at x approximately equal to 0.02-0.05, Bhf decreases with increasing x.

Published
1992

47. Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy

Author

Salazar-Alvarez, G., Qin, J., Sepelak, V., Bergmann, I., Vasilakaki, M., Trohidou, K.N., Ardisson, J.D., Macedo, W.A.A., Mikhaylova, M., Muhammed, M., Baro, M.D., and Nogues, J.

Subjects
Anisotropy -- Analysis, Iron compounds -- Magnetic properties, Iron compounds -- Structure, Nanoparticles -- Structure, Nanoparticles -- Magnetic properties, Chemistry
Abstract

Experimental and theoretical studies were conducted to understand the magnetic properties of maghemite ([gamma]-[Fe.sub.2][O.sub.3]) cubic and spherical nanoparticles of similar sizes. The results obtained provide insight into the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of [gamma]-[Fe.sub.2][O.sub.3] which is the origin of these effects.

Published
2008

50. Structural and magnetic properties of the half-ferromagnetic Co2+x+yMn1-xAl1-y alloys

Author

Paduani, C., Migliavacca, A., Krause, J.C., Ardisson, J.D., and Yoshida, M.I.

Subjects
Half-ferromagnetic materials, Condensed Matter::Materials Science, Manganese, Heusler alloys, Condensed Matter::Strongly Correlated Electrons, Cobalt, Aluminum
Abstract

Co2+x+yMn1-xAl1-y intermetallic compounds have been prepared by arc melting and studied with X-ray diffraction and magnetization measurements to ascertain the effect of deviations of composition from the stoichiometry on the ferromagnetism of this system. Hysteresis loops registered at room temperature show a soft ferromagnetic behavior in excess Co. In off-stoichiometric alloys the saturation magnetization is lower than in Co2MnAl, whereas the Curie temperature T C is higher in all the studied alloys. T C varies substantially with variations in composition and increases with the Mn content. In the source of this behavior a volume effect is inferred which is expected to lead to strengthened ferromagnetic exchanges.

Published
2007

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