Infrared absorption spectra of La0.67-xPrxCa0.33MnO3 （x= 0, 0.18 and 0.36） are experimentally studied in the temperature range 20 -300K. Absorption peak splitting corresponding to the stretching oscillation of the M...Infrared absorption spectra of La0.67-xPrxCa0.33MnO3 （x= 0, 0.18 and 0.36） are experimentally studied in the temperature range 20 -300K. Absorption peak splitting corresponding to the stretching oscillation of the Mn-O bond, together with a shift of peak position, is observed below the Curie temperature. These features weaken and even disappear as the samples are warmed up to the Curie temperature, which indicates that this anomaly may be a result of phase separation in the compounds.展开更多
采用紫外脉冲激光沉积技术分别在LaA lO 3(LAO)、(LaA lO 3)0.3-(SrA lT aO 6)0.7(LSAT)和SrT iO 3(STO)(001)单晶衬底上制备了La0.825Ca0.175MnO 3(LCMO)薄膜。实验发现衬底的晶格失配度和退火氧压对薄膜结晶质量和电学性能有重要影响...采用紫外脉冲激光沉积技术分别在LaA lO 3(LAO)、(LaA lO 3)0.3-(SrA lT aO 6)0.7(LSAT)和SrT iO 3(STO)(001)单晶衬底上制备了La0.825Ca0.175MnO 3(LCMO)薄膜。实验发现衬底的晶格失配度和退火氧压对薄膜结晶质量和电学性能有重要影响。电阻-温度曲线显示,生长在LAO(压应变)的LCMO薄膜比生长在STO(拉伸应变)的薄膜有更高的绝缘体-金属转变温度Tp和更大的电阻温度系数(TCR)。增加退火氧压可以有效地提高薄膜的Tp和TCR值。当退火氧压为30000 Pa时,与衬底晶格失配度最小的LCMO/LSAT薄膜具有最高的Tp(234.5 K)和最大的TCR(22.4%)。实验结果表明Ca含量为0.175的La1-xCaxMnO 3薄膜材料在测辐射热计等方面有潜在的应用前景。展开更多
The resistivity of the heavy-doped La1/3Ca2/3MnO3 （LCMO） is simulated using a random resistor network model, based on a phase separation scenario. The simulated results agree well with the reported experimental data...The resistivity of the heavy-doped La1/3Ca2/3MnO3 （LCMO） is simulated using a random resistor network model, based on a phase separation scenario. The simulated results agree well with the reported experimental data, showing a transition from a charge-disordered （CDO） state embedded with a few ferromagnetic （FM） metallic clusters to a charge-ordered （CO） state, corresponding to the transition from a high-temperature paramagnetic （PM） insulating state to a low-temperature antiferromagnetic （AF） insulating state. Furthermore, we find that the number of AF/CO clusters increases with decreasing temperature, and the clusters start to connect to each other around 250K, which causes percolating in the system. The results further verify that phase separation plays a crucial role in the electrical conductivity of LCMO.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos G50225209 and G50271023, the Key Foundation of Education Ministry of China under Grant G02017 and the Natural Science Foundation of Hebei Province under Grant No G503031.
文摘Infrared absorption spectra of La0.67-xPrxCa0.33MnO3 （x= 0, 0.18 and 0.36） are experimentally studied in the temperature range 20 -300K. Absorption peak splitting corresponding to the stretching oscillation of the Mn-O bond, together with a shift of peak position, is observed below the Curie temperature. These features weaken and even disappear as the samples are warmed up to the Curie temperature, which indicates that this anomaly may be a result of phase separation in the compounds.
基金General Project of Science and Technology Department of Yunnan Province(KKSA201151081)
文摘采用紫外脉冲激光沉积技术分别在LaA lO 3(LAO)、(LaA lO 3)0.3-(SrA lT aO 6)0.7(LSAT)和SrT iO 3(STO)(001)单晶衬底上制备了La0.825Ca0.175MnO 3(LCMO)薄膜。实验发现衬底的晶格失配度和退火氧压对薄膜结晶质量和电学性能有重要影响。电阻-温度曲线显示,生长在LAO(压应变)的LCMO薄膜比生长在STO(拉伸应变)的薄膜有更高的绝缘体-金属转变温度Tp和更大的电阻温度系数(TCR)。增加退火氧压可以有效地提高薄膜的Tp和TCR值。当退火氧压为30000 Pa时,与衬底晶格失配度最小的LCMO/LSAT薄膜具有最高的Tp(234.5 K)和最大的TCR(22.4%)。实验结果表明Ca含量为0.175的La1-xCaxMnO 3薄膜材料在测辐射热计等方面有潜在的应用前景。
基金Supported by the National Natural Science Foundation of China under Grant No 10334070. We would like to thank Professor Jin K. J. for her helpful discussion.
文摘The resistivity of the heavy-doped La1/3Ca2/3MnO3 （LCMO） is simulated using a random resistor network model, based on a phase separation scenario. The simulated results agree well with the reported experimental data, showing a transition from a charge-disordered （CDO） state embedded with a few ferromagnetic （FM） metallic clusters to a charge-ordered （CO） state, corresponding to the transition from a high-temperature paramagnetic （PM） insulating state to a low-temperature antiferromagnetic （AF） insulating state. Furthermore, we find that the number of AF/CO clusters increases with decreasing temperature, and the clusters start to connect to each other around 250K, which causes percolating in the system. The results further verify that phase separation plays a crucial role in the electrical conductivity of LCMO.
