Mn的价态对La0.8Ba0.2MnO3电磁性能的影响

在2—390K温度之间研究了La_0.8Ba_0.2MnO₃的 磁矩、磁电阻与温度的关系.发 现以不同价态的Mn元素引入得到的La_0.8Ba_0．2MnO₃ ，性能虽然都存在金属 —绝缘体转变，以及在磁场作用下居里温度附近电阻率变化非常显著的特点，但是价态对磁 性转变温度T_C，金属—绝缘体转变温度T_mi，以及磁电阻极大 值温度T_MR的影 响都非常显著.三种价态相比较，使用二价Mn的电阻率最低以及磁性转变温度更接近室温.认 为影响材料性能的主要因素是材料制备时引进的Mn元素的价态，由于原料价态的不同而形成 的氧空位浓度变化，进而影响了Mn⁴⁺/Mn³⁺的比.关键词：价态磁电阻居里温度金属—绝缘体转变

Dependence of magnetoelectric properties of La0.8Ba0.2MnO3 on Mn valence of oxide precursors

The influence of temperature (in the range of 2—390K) on the magnetic moment,and magnetoresistance has been investigated in this paper. It is found that the magnetoelectric properties, particularly the Curie temperature T_C, th e metal-insulator transition temperature, T_mi, and the maximum m agnetoresistance T_MR, of La_0.8Ba_0.2MnO ₃ are closely related to the valence of Mn in the oxides. La_0.８Ba_０.2M nO₃ synthesize d with 2⁺ Mn oxides exhibited the lower resistivity, and a Curie temp erature c loser to room temperature (290K) compared with that synthesized with 3^{+ Mn ox ides. It can be concluded that the magnetoelectric properties of La_{0.8< /sub>Ba 0.2MnO3 are dependent on the Mn valence of oxides. This cou ld be attribut ed to the influence of oxygen vacancy concentration variation on the Mn4+ /M n3+ ratio in the resultant compounds during solid sintering react ion, which results from the valence difference of oxide precursors.}}