Fe掺杂对La_(0.67)Sr_(0.33)CoO_3磁电性质的影响

Influence of Fe Doping on the Magnetic,Eletrical Properties in La_(0.67)Sr_(0.33)CoO_3

通过磁性、电子输运和磁电阻等性质的测量，我们研究了 La0.67Sr0.33CoO3的 Fe掺杂效应。发现当 Fe掺杂直到 x=0.3时，样品的结构没有明显变化，但掺杂将降低居里温度 Tc和磁化强度 M。电阻率在低掺杂（ x 0.1）时显示金属性输运行为，而在高掺杂（ x=0.2和 0.3）时则显示半导体行为。而且， Fe掺杂削弱了居里温度 Tc处的 MR峰值，但增加了低温下（ T Tc）的 MR值。 La0.67Sr0.33CoO3的 Fe掺杂效应和磁电阻的起源可由外加磁场导致的自旋态转变来解释。

The effects of Fe doping in La0.67Sr0.33CoO3 have been studied by the measurments of magnetic,eletrical transport, and magnetoresistance properties. It is found that no apparent structure change is introduced by Fe doping up to x=0.3. But the Curic temperature Tc and magnetization M are strongly lowered by Fe substitution. The eletrical resistivity exhibits metallic behavior in low－ doped (x 0.1) samples while semiconducting behavior in high－ doped(x=0.2 and 0.3) samples. In addition, Fe doping weakens the MR peak near Tc but enhances the low－ temperature MR. The origin of CMR and the effect of Fe doping in La0.67Sr0.33CoO3 are interpreted in terms of the spin－ state transition induced by applied magnetic fields.