ELECTRICAL-RESISTANCE MAXIMUM NEAR THE CURIE-POINT IN (FE1-XVX)3GA AND (FE1-XTIX)3GA

The electrical resistivity of the D03-type (Fe1-xVx)3Ga and (Fe1-xTix)3Ga alloys has been measured over the temperature range from 4.2 to 1250 K. The temperature dependence of the resistivity shows an anomaly that has been found in ferromagnetic 3d alloys: an appearance of the resistance maximum near the Curie point and the negative temperature dependence at high temperatures up to 1000 K and above. The tendency of the negative temperature dependence of the resistivity increases markedly with increasing the V or Ti composition. Such an anomalous resistance behavior cannot be accounted for in terms of an order-disorder transformation, since the decrease in the resistivity occurs even below room temperature. At a temperature higher than 800 K, a stepwise reduction of the resistivity appears as a sign of the transformation, which terminates the negative-temperature-coefficient range. Close examination of various components of the resistivity reveals that the magnetic scattering resistance is five to ten times as large as those of ordinary ferromagnetic 3d alloys and that the residual resistivity increases at an extremely large rate of 12-mu-OMEGA-cm for at.% V and 14-mu-OMEGA-cm for at.% Ti in the respective alloys. It is concluded that (Fe1-xMx)3Ga (M = V and Ti) is a type of conductor not to be classified into several other types of metallic conductors hitherto known to exhibit a negative temperature coefficient of resistivity.