Das Rajasree, Chanda Amit, Mahendiran Ramanathan
Department of Physics, Faculty of Science, National University of Singapore 2 Science Drive 3 Singapore - 117542 Republic of Singapore
RSC Adv. 2019 Jan 14;9(3):1726-1733. doi: 10.1039/c8ra08694j. eCollection 2019 Jan 9.
We report the magnetization (), magnetostriction, electrical resistivity (), thermal conductivity () and thermopower () of polycrystalline LaNaMnO over a wide temperature range of 5 to 360 K. This sample undergoes a paramagnetic to ferromagnetic transition around = 274 K and electrical resistivity shows an insulator-metal transition around = 292 K. The sign of thermopower is positive in the entire temperature range which indicates that majority charge carriers are holes. Thermopower exhibits a peak and thermal conductivity shows a dip at in the absence of magnetic field. Large difference between the experimentally determined activation energies of and in the insulating state indicates small polaron hopping dominant conduction above . Polaron formation above , was further confirmed from the anomaly observed in thermal expansion (Δ/ ) which shows a change in slope at . In the vicinity of at 3 T applied field, magneto-thermopower (∼61.5%) is larger than magnetothermal conductivity (∼12.7%) and magnetoresistance (∼49%).
我们报告了多晶LaNaMnO在5至360 K的宽温度范围内的磁化强度（）、磁致伸缩、电阻率（）、热导率（）和热电势（）。该样品在 = 274 K左右经历顺磁到铁磁转变，电阻率 在 = 292 K左右显示绝缘体 - 金属转变。热电势 的符号在整个温度范围内为正，这表明多数载流子是空穴。在无磁场时，热电势在 处出现峰值，热导率在 处出现下降。在绝缘状态下，实验测定的 和 的激活能之间的巨大差异表明，高于 时小极化子跳跃主导传导。高于 时极化子的形成，从热膨胀（Δ/ ）中观察到的异常进一步得到证实，该异常在 处显示斜率变化。在3 T外加磁场下接近 时，磁热电势（约61.5%）大于磁热导率（约12.7%）和磁电阻（约49%）。
