Low temperature electron-diffusion magnetothermopower of aluminium. I. Experiment

Measurements have been made of the magnetothermopower S of an aluminum single crystal containing 50 PPM of gallium, in transverse magnetic fields H up to 20 kG, at temperatures T between 1.5 and 5.0K. The data were consistent with the equation S(H,T)=A(H)T+B(H)T 3 , allowing a separation of the electron diffusion component, S d (H)=A(H)T, from the phonon drag component, S g (H)=B(H)T 3 . This separation allowed determination of the quantity Delta S d =S d (H to infinity )-S d (H=0). The average value of Delta S d for H along the crystallographically equivalent (010) and (001) axes was Delta S d =(2.23+or-0.25)T*10 -8 VK -1 , in good agreement with the calculation by Opsal and Wagner which included a 45% electron-phonon mass enhancement. For H along the (011) family of axes, a value of Delta S d =(2.0+or-0.2)T*10 -8 VK -1 was obtained. This value is slightly lower than the average value of Delta S d for H along the (101) axes, in agreement with the calculation of Opsal and Wagner.