La_(1-x)Sr_xMnO_3氧化物磁导率和介电常数的频率特性研究

Investigation on Complex Permittivity and Permeability of La_(1-x)Sr_xMnO_3 Oxides

采用溶胶．凝胶法制备了钙钛矿型La1-xSrxMnO3（x=0，0．2，0．4，0．6）氧化物多晶样品，样品粉料的平均粒径为70nm左右。对不同Sr含量的样品磁导率μr（μr=μ＇r＋iμ＂r）和介电常数εr（εr=ε＇r＋iε＂r）的频谱（50～1800MHz）的研究表明，不掺Sr时，LaMnO3氧化物的复磁导率不随着频率变化，其实部近似为0．8，而虚部近似为1．0，复介电常数却随着频率增加而单调下降，实部从33降到19，虚部从65降到5。掺入Sr后，复磁导率和复介电常数频谱曲线都为典型的弛豫型谱线，磁导率的共振频率随着掺杂增加从1420MHz减小到810MHz，而复介电常数的共振频率却随着Sr含量增加从231MHz增加到580MHz，并对相关动态磁化和电极化机制进行了讨论。

La1-xSrxMnO3（x = 0, 0.2, 0.4, 0.6） oxides were prepared through sol-gel method with even crystalline size 70 nm, complex permittivity and permeability behavior dependence on Sr contents in the range of 50 - 1800 MHz were discussed. When x = 0, for LaMnO3 oxide, the complex permeability keeps a constant number, μ＇r≌0.8, μ＂r≌1.0 in the frequency range of 50 - 1800 MHz; the complex permittivity decreases as frequency increases, the ε＇r decreases from 33 to 19 and the ε＂r decreases from 65 to 5.However, when the specimen doped with Sr, it exhibits a relaxation character from the frequency spectrum curves of the complex pennittivity and permeability. Moreover, the resonance frequency fr of the complex permeability decreases from 1420 to 809 MHz with Sr content increasing from 0.2 to 0.6, and the fr of the complex pennittivity increases from 231 to 580 MHz as Sr content increases from 0.2 to 0.6. Furthermore, the mechanism of the AC magnetization and AC electric polarization were discussed.