Effect of Order on the Hall Constants ofNi3Mn

Hall effect measurements as a function of temperature are reported for ordered and disordered ${\mathrm{Ni}}_3$Mn. At low temperatures the ordinary Hall coefficient is found to be negative for both the ordered and disordered alloy. It is shown that the apparent positive value of the ordinary Hall coefficient in the disordered alloy at room temperature is due to the near coincidence of the Curie temperature of this alloy with room temperature. This results in a positive contribution to the measured value of the ordinary Hall coefficient from the extraordinary effect, a smaller contribution being present at low temperatures. An approximate correction is made for this contribution, with the result that the true ordinary coefficient in disordered ${\mathrm{Ni}}_3$Mn is found to be nearly equal to that in the ordered alloy. Furthermore, its absolute magnitude and temperature dependence are much like that of Cu-Ni and pseudonickel alloys. On this basis it is concluded that ordering has much less effect on the band structure of this alloy than was previously assumed.