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实验研究了晶粒间弱连接和致密连接的Ｌａ０．８５Ｎａ０．１７ＭｎＯｚ多晶样品的电磁性质，发现 弱连接的样品和致密连接的样品在居里温度以下的输运性质显著不同，弱连接的样品从居 里温度到 ７７ Ｋ在低场下具有较大的磁电阻，而致密连接的样品在低温的磁电阻几乎为零． 结合低温下的电阻率与外磁场的关系，可以得出，晶粒间的自旋相关的隧道效应对低温的 低场磁电阻起着重要作用．
The electromagnetic properties of La0.85Na0.17MnOz polycrystalline samples with weakly connected and densely connected grains were studied experimentally. It was found that the transport properties of weakly connected samples and densely-connected samples were significantly different under the Curie temperature. The weakly connected samples From Curie temperature to 77 K, there is a large magnetoresistance in low field, whereas in densely connected samples the magnetoresistance at low temperature is almost zero. Combining the relationship between the resistivity and the external magnetic field at low temperature, it can be concluded that the spin-related tunneling effect between the grains plays an important role in the low-temperature low-field magnetoresistance.