我們測量了一系列以電化學方法合成的阿爾發結構二氧化錳的樣品，這些樣品分別在阿爾發結構二氧化錳的通道中摻雜了不同的鹼金屬離子。X射線繞射結果顯示這些樣品具有阿爾發結構的純相。我們以ICP跟EDS定出通道中離子的含量，其含量與離子大小相關。在磁性的測量上，所有的樣品表現出超順磁的行為。超順磁的轉變溫度與通道中離子大小以及樣品晶粒大小有關。摻雜鉀離子的樣品，其磁化率曲線在低溫往上翹，與其他的樣品在低溫的行為上有很明顯的不同。此外，其零場冷磁化率要高過場冷磁化率，這點相當的異常。我們以鉀離子在通道中比較窄的部份能有效的減低各向異性來解釋其低溫磁化率往上翹的趨勢。我們也測量了摻雜鉀離子阿爾發結構二氧化錳的塊材的傳輸性質。其電阻符合可變跳躍範圍理論的式子。在磁阻上，以250□C燒結的樣品較接近三維庫倫能隙理論的預測，而以350□C燒結的樣品，其磁阻較無明顯變化。

A series of □-MnO2 samples with different counter ions in the tunnel were synthesized. The X-ray diffraction pattern shows the pure phase of the samples. The content of counter ions were determined by both ICP□AES and EDS. The content depends on the ionic size. The magnetic properties show the superparamagnetic transition for all samples. The blocking temperature depends on the ionic size of counter ions and grain size. The sample with K+ as main cations in the tunnel shows anomaly with an apparent upturn below the transition. In addition, the ZFC susceptibility is larger than the FC susceptibility. We explain the upturn by the suppressing of anisotropy at the bottleneck. The temperature dependence of resistivity of the KxMnO2 bulks with being sintered follows the general variable range hopping formula. The magnetoresistivity of the bulk sintered at 250□C is consistent with the prediction of three-dimensional variable range hopping with Coulomb gap. On the other hand, the exponent in the general variable range hopping formula is nearly independent of magnetic fields up to 7 Tesla.

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