Small Polaron Hopping Conduction in Samples of Ceramic ＄La_{1.4}Sr_{1.6}Mn_{2}O_{7.06}＄

概要

論文の詳細を見る
The ceramic sample of ＄La_{1・4}Sr_{1・6}Mn_{2}O_{7 · 06}＄exhibits the metal-insulator transition and a negative magnetoresustance in the vicinity of the Curie temperature (Tc＄simeq＄ 100K). The dcmagnetic susveptibility between 100 K and 280 K is nearly constant and decreases gradually eith increasing temperatire above 280 K. The measurements of dc resistivity and the thermoelectric power indicate that small polaron hoppong conduction takes place at T > 280 K.The spin order due to the two-dimensional ＄d_{x^2-Y^2}＄ state occurring at T>280 K is directly related to the hopping conduction above 280 K, although the spin ordering due to the one-dimensional ＄d_{3z^2-r^2}＄ state takes place at T>Tc.The two-dimensional ＄d_{x^2-y^2}＄state ectending within the ＄MnO_{2}＄ sheets starts to narrow and leads to the carrier localisation at 208 K.The effective number of holes in this sample estimated from the thermoelectric power is considerably smaller than the nominal value. This indicates that the small polaron hopping conduction takes olace predominantly within the in-plane ＄MnO_{2}＄ sheets. A discussion is given of the experimental results of the ceramic sample of ＄La_{2/3}Ca_{1/3}Mno_{2・98}.
CSIRO PUBLISHINGの論文