IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
artículos
Título:
Curie temperature and Hopkinson effect in twin roller melt spun Ni2MnGa shape memory alloys
Autor/es:
G. POZO LÓPEZ; L.M. FABIETTI; A.M. CONDÓ; E. WINKLER; R.N. GIORDANO; N. HABERKORN; S.E. URRETA
Revista:
IEEE TRANSACTIONS ON MAGNETICS
Editorial:
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Referencias:
Lugar: New York; Año: 2013 vol. 49 p. 4514 - 4517
ISSN:
0018-9464
Resumen:
The temperature dependence of the magnetic polarization near the Curie temperature TC in Ni2MnGa stoichiometric alloys, directly processed from the melt in a twin-roller melt-spinning device, is investigated. The effect of the solidification rate on the Hopkinson peak detected is evaluated in samples quenched at three different tangential wheel speeds of 10 m/s, 15 m/s and 20 m/s. The resulting microstructures were previously characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDS) and by transmission electron microscopy (TEM). EDS results indicated that all the alloys have the composition Ni2MnGa; at room temperature and above this temperature, a cubic L21 ferromagnetic ordered austenitic phase is observed. The Curie temperatures and the magnitude of the Hopkinson effect are estimated from the magnetic polarization vs. temperature curves measured in a Faraday balance, in the range 300 K- 400 K. As expected for samples with identical composition, the Curie temperatures remain insensitive to the processing route. At low fields (10 mT), the magnitude of the Hopkinson effect is larger in samples quenched at lower rates and it practically vanishes in all the alloys for applied fields near 100 mT.