화학공학소재연구정보센터
Materials Science Forum, Vol.373-3, 597-600, 2001
Transport properties of ordered and disordered CoAl and CoTi alloy films
The influence of structural disorder on the transport properties of CoAl and CoTi alloy films were investigated. CoAl and CoTi alloy films with a total thickness of about 100 mn were prepared by flash evaporation of the crushed alloy powders onto heated (730 K for the ordered state) and LN2-cooled (150 K for the disordered state) substrates. Structural analysis of the films was performed by transmission electron microscopy. The resistivity measurements were carried out by using the four-probe technique in a temperature range of 4.2 - 300 K with and without an external magnetic field. The magnetic properties were also studied in a temperature range of 77 - 300 K. It was found that the temperature dependence of resistivity exhibits a significantly different behavior according to the degree of long range order. While both ordered and disordered CoAl films show a prominent resistivity minimum in the low-temperature region, the location shifts to a high temperature in the disordered alloy film. In case of CoTi alloy films, there is no prominent resistivity minimum. At the same time, the structural disorder leads to a change in temperature coefficient of resistivity from a positive to negative value. The behavior of the temperature dependence of these alloy films are not affected by the presence of external magnetic field. The results are analyzed in connection with the change in electronic structures and the possible transport mechanisms are discussed.