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首页> 外文期刊>Physica, B. Condensed Matter >The ac transport and giant magnetoimpedance for sol-gel La _(0.67)Ca _(0.33)MnO _3
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The ac transport and giant magnetoimpedance for sol-gel La _(0.67)Ca _(0.33)MnO _3

机译：溶胶-凝胶La _（0.67）Ca _（0.33）MnO _3的交流输运和巨磁阻抗

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摘要

In the present work, the temperature dependences of ac transport and magnetoimpedance for sol-gel La _(0.67)Ca _(0.33)MnO _3 manganite are investigated at various frequencies. The ac resistance R with absence of field shows a peak around the metal-insulator transition temperature T _(MI) for the dc case. A low magnetic field can shift the metal-insulator transition temperature more easily at high frequency than at low frequency. The valley phenomenon is observed in the temperature dependence of reactance X at 2 and 4 MHz, showing the effects of phase separation or grain boundaries. At 30 MHz, the peak of X appears instead of the valley, since the contribution of insulator capacitance term drops greatly and the inductance of metal dominates the X term with an increase of ac frequency in the sample. At 2 and 4 MHz, La _(0.67)Ca _(0.33)MnO _3 sol-gel manganite under H=1 kOe shows negative ac magnetoresistance ΔR/R _0, magnetoreactance ΔX/X _0 and magnetoimpedance ΔZ/Z _0 below 275 K, but positive ac ΔR/R _0, ΔX/X _0 and ΔZ/Z _0 near room temperature much higher than the Curie temperature. The peak temperature of R/R _0 moves to low temperature with an increase of the ac frequency from 2 to 4 MHz. At f=30 MHz, the absolute value of negative ac ΔR/R _0 increases monotonically with a decrease of temperature for 175 K
机译：在目前的工作中，研究了在不同频率下溶胶-凝胶La _（0.67）Ca _（0.33）MnO _3锰矿的交流输运和磁阻的温度依赖性。在没有磁场的情况下，交流电阻R在直流情况下在金属绝缘体转变温度T _（MI）附近出现一个峰值。与低频相比，低磁场在高频下更容易移动金属-绝缘体的转变温度。在2和4 MHz的电抗X的温度依赖性中观察到谷值现象，显示出相分离或晶界的影响。在30 MHz处，X的峰值出现而不是谷值，这是因为绝缘子电容项的贡献大大降低，并且金属的电感在X项中占主导地位，随着样品中ac频率的增加。在2 MHz和4 MHz时，在H = 1 kOe下La _（0.67）Ca _（0.33）MnO _3溶胶-凝胶锰矿显示出负的ac磁阻ΔR/ R _0，磁阻ΔX/ X _0和磁阻ΔZ/ Z _0低于275 K ，但室温附近的正acΔR/ R _0，ΔX/ X _0和ΔZ/ Z _0远高于居里温度。随着交流频率从2 MHz增加到4 MHz，R / R _0的峰值温度变为低温。在f = 30 MHz时，对于175 K

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