La0和La1-xSrxMnO3（x = 0.18-0.5）的自发和低场磁阻抗效应
Spontaneous and low-field magnetoimpedance in La0.7Sr0.3CoO3 and La1-xSrxMnO3 (x = 0.18-0.5)
摘要：
我们报告交流电输运在La 0.7Sr 0.3CoO3和La 1-xSrxMnO 3（x = 0.18- 0.5）作为温度和频率的函数在H = 0和60 mT。测量阻抗（Z = R+jX）的电阻（R）和电抗（X）分量。结果表明，La_（0.7）Sr_（0.3）CoO_3的电阻在居里温度附近随频率的增加由一个平稳的下降转变为一个突然的上升，并在R值附近出现一个峰值。在La-Sr-MnO 3系列的金属组合物中也发现了R的类似行为。在TC观测到的异常被H = 60 mT的小直流磁场抑制，这导致巨大的交流磁阻（f = 2 MHz时，锰氧化物= 30%，钴氧化物= 7%）。零场中R的异常也伴随着X的突然增大。虽然交流磁阻是负的作为从100 Hz到30 MHz的场的函数，我们表明，X的符号的变化和一个新的双峰结构的发展，在X为15 MHz以上的频率。
英文摘要：
We report ac electrical transport in La0.7Sr0.3CoO3 and La1-xSrxMnO3 (x = 0.18- 0.5) as a function of temperature and frequency in H = 0 and 60 mT. Both resistive (R) and reactive (X) components of impedance (Z = R+jX) were measured. It is shown that a smooth decrease of the resistance around the Curie temperautre in La0.7Sr0.3CoO3 transforms into an abrupt increase followed closely by a peak in R with increasing frequency. Similar behavior in R was also found in metallic compositions of the La-Sr-MnO3 series. The observed anomaly at TC is suppressed by a small dc magnetic field of H = 60 mT which rrsults in a huge ac magnetoreistance (= 30 % in manganite and =7 % in cobaltite at f = 2 MHz). The anomaly in R in zero field is also accompanied by a sudden incrases of X. While the ac magnetoresitance is negative as a function of field from 100 Hz to 30 MHz, we show that the sign of X changes and a new double peak structure develops in X for frequencies above 15 MHz.
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