IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Low temperature electrical resistance in Nd60Fe30Al10 melt spun alloys
Autor/es:
H. R. SALVA; M. VILLAFUERTE; G. POZO LÓPEZ; L. M. FABIETTI; S. HELUANI; A. A. GHILARDUCCI; S. E. URRETA
Lugar:
Comisión Nacional de Energía Atómica. San Martín, Pcia. de Buenos Aires, Argentina
Reunión:
Congreso; At the Frontiers of Condensed Matter IV: Current Trends and Novel Materials; 2008
Resumen:
Melt spun Nd60Fe30Al10 glass forming alloys are known to contain small hcpNd crystals, very small crystalline motes (1.2 ± 0.5 nm) of a Nd6Fe14-xAlx (2 < x < 5.5) d-type phase and small clusters of a metastable µ-type (Nd37Fe58Al5) crystalline phase, all embedded in an amorphous matrix. These alloys show coercivities up to 0.5 T at room temperature, arising in this rather complex nanostructure, which is very sensitive to the quenching rate. In this article we report the behavior of the electrical resistivity observed, in the 4K-300K range, in Nd60Fe30Al10 samples melt spun at different wheel speeds, between 5 m/s to 40 m/s. In the ribbons cooled at 5 m/s the electrical resistance monotonously increases with temperature, exhibiting a metallic regime in the entire temperature range. For quenching rates above 20m/s and up to 40 m/s, the resistance curve goes thruogh a maximum at about 80K, passing from a metallic behavior at low temperatures to a semiconductor-like regime, with resistance monotonously decreasing as temperature increases up to 300 K. The magnetic hysteresis properties of the samples cooled at di.erent rates were measured in the same temperature range and then correlated with the electrical transport behavior observed. It is found that the features observed in the resistance curves are likely to be connected with the magnetic ordering in the d phase (a paramagnetic to antiferromagnetic transition near 270 K and a spin reorientation transformation near 80K). a spin reorientation transformation near 80K).d-type phase and small clusters of a metastable µ-type (Nd37Fe58Al5) crystalline phase, all embedded in an amorphous matrix. These alloys show coercivities up to 0.5 T at room temperature, arising in this rather complex nanostructure, which is very sensitive to the quenching rate. In this article we report the behavior of the electrical resistivity observed, in the 4K-300K range, in Nd60Fe30Al10 samples melt spun at different wheel speeds, between 5 m/s to 40 m/s. In the ribbons cooled at 5 m/s the electrical resistance monotonously increases with temperature, exhibiting a metallic regime in the entire temperature range. For quenching rates above 20m/s and up to 40 m/s, the resistance curve goes thruogh a maximum at about 80K, passing from a metallic behavior at low temperatures to a semiconductor-like regime, with resistance monotonously decreasing as temperature increases up to 300 K. The magnetic hysteresis properties of the samples cooled at di.erent rates were measured in the same temperature range and then correlated with the electrical transport behavior observed. It is found that the features observed in the resistance curves are likely to be connected with the magnetic ordering in the d phase (a paramagnetic to antiferromagnetic transition near 270 K and a spin reorientation transformation near 80K). a spin reorientation transformation near 80K). samples melt spun at different wheel speeds, between 5 m/s to 40 m/s. In the ribbons cooled at 5 m/s the electrical resistance monotonously increases with temperature, exhibiting a metallic regime in the entire temperature range. For quenching rates above 20m/s and up to 40 m/s, the resistance curve goes thruogh a maximum at about 80K, passing from a metallic behavior at low temperatures to a semiconductor-like regime, with resistance monotonously decreasing as temperature increases up to 300 K. The magnetic hysteresis properties of the samples cooled at di.erent rates were measured in the same temperature range and then correlated with the electrical transport behavior observed. It is found that the features observed in the resistance curves are likely to be connected with the magnetic ordering in the d phase (a paramagnetic to antiferromagnetic transition near 270 K and a spin reorientation transformation near 80K). a spin reorientation transformation near 80K).