DETERMINATION OF THE BAND-STRUCTURE OF PB1-X-YSNYMNXTE SEMIMAGNETIC SEMICONDUCTORS FROM THERMOELECTRIC-POWER STUDIES

Thermoelectric power and Hall effect were measured for Pb1-x-ySnyMnxTe samples with 0.00 less than or equal to x less than or equal to 0.12 and 0.72 less than or equal to y less than or equal to 0.80, with carr ier concentration 1.9 x 10(20) less than or equal to p less than or eq ual to 2.5 x 10(21) cm(-3) over a temperature range T = 4.2-300 K, The analysis of the experimental data based on a two-valence-band model w as performed, The theoretical description of the light holes of the L band is based on the Dimmock model. For heavy holes from the Sigma ban d the parabolic dispersion relation was assumed. Our analysis indicate s that with increasing Mn content the energy gap (E-g) increases: part ial derivative E-g/partial derivative x = 25 meV at.%(-1), whereas the energy separation between the bands of light and heavy holes (E-Sigma ) decreases: partial derivative E-Sigma/partial derivative x = -12 meV at.%(-1). We also observe an increase of the effective mass of heavy holes (m(Sigma)) from m(Sigma) = (1.0 +/- 0.25)m(0) for samples with x less than or equal to 0.09 to m(Sigma) = 2.1 m(0) for x = 0.12.