Determination of the band structure of semimagnetic semiconductors from thermoelectric power studies

Abstract

Thermoelectric power and Hall effect were measured for Pb 1−x −y Sn y Mn x Te samples with 0.00 ≤ x ≤ 0.12 and 0.72 ≤ y ≤ 0.80, with carrier concentration 1.9 × 10 20 ≤ p ≤ 2.5 × 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 was performed. The theoretical description of the light holes of the L band is based on the Dimmock model. For heavy holes from the band the parabolic dispersion relation was assumed. Our analysis indicates that with increasing Mn content the energy gap (E g ) increases: ∂E g /∂x = 25 meV at.% −1 , whereas the energy separation between the bands of light and heavy holes (E ) decreases: ∂E /∂x = −12 meV at.% −1 . We also observe an increase of the effective mass of heavy holes (m ) from m = (1.0 ± 0.25)m 0 for samples with x ≤ 0.09 to m = 2.1m 0 for x = 0.12.

Pb1-xMnxTe Crystals as a New Thermoelectric Material

“…Such enhancement of thermoelectric power can be connected with an increase in the effective mass of heavy holes with increasing Mn content. The attempt to determine the Mn concentration dependence of the effective mass of the density of states of heavy holes was undertaken in [10].…”

Sm-substitution effects on structural and transport properties of PbSe

“…A broad search has been under way to identify new materials with enhanced thermoelectric properties. Several classes of materials are currently under investigation including lead chalcogenides [1][2][3][4][5][6][7][8][9]. They have received great attention, as candidate thermoelectric materials because of their high power factor and their potential for high temperatures applications with promising thermoelectric performance.…”

Thermoelectric properties of Pb0.75−xMnxSn0.25Te alloys with variable manganese content

“…The band structure of PbMnSnTe system has been studied by Lazaryck et al [20] at low temperature (4.2 K-300 K) for samples with variable Mn content and Sn content 40.72. The band structure of PbMnSnTe is analogous to that of PbSnTe i.e.…”

“…The phase diagram of PbTe-MnTe alloys has been studied [15] and isotherms of thermal conductivity of PbTe-MnTe have been studied for low Mn content [16]. Substitution of small amount of Mn in Pb 1À y Sn y Te turns it into a dilute magnetic semiconductor and hence, its studies have been confined to low temperatures (o300 K) with an emphasis on magnetic properties [17][18][19], though the thermopower has been measured upto 300 K [20]. This is much lower than the temperatures at which these materials find thermoelectric application.…”

“…Fourthly, substitution of isovalent Mn at Sn site could help in reducing κ l by mass fluctuation scattering. Moreover, the electronic band structure [20] and magnetic phase diagrams [23] of the system PbMnSnTe have been determined before with Sn content 4y¼0.5 in both the cases but the studies were limited to 300 K and there are no reports on high temperature thermoelectric properties of PbMnSnTe system with Sn content o0.5.…”