Kang Baojuan

Nano-sized Domain Wall Pinning Effects in Dilute Cu-Doped Perovskite LaMn1-xCuxO3 Manganites

Magnetic properties of Cu-doped LaMn1-xCuxO3 (x=0.05-0.30) systems are carefully studied in the temperature range of 2–300 K. A visible unexpected drop is observed in the ac susceptibility and the zero-field cooled dc magnetization curves for the dilute x ≤0.10 near 100K, which depends on the measuring frequency and magnetic field. Measurements on frequency dependence of ac susceptibility, observation of magnetic relaxation, and the existence of critical field indicate that the anomaly can be attributed to the domain wall pinning effects. This is directly proven by the results of ball milled nano-sized powder counterparts compared with the bulk materials.

Ho 0.5 Pr 0.5 FeO 3 的磁性与巨磁介电效应

采用固相反应法制备了Ho 0.5 Pr 0.5 FeO 3 多晶样品, 对其磁性和磁介电特性进行了系统研究。在 T =4.5 K附近存在Ho离子的反铁磁相变, 在T= 59 ~80K可观测到Fe离子的自旋重取向转变, 磁滞回线表明样品呈现弱铁磁性。在 T = 270 K, 介电常数可达~10 3 , 研究表明该介电常数与270 K附近的电阻变化相关联, 该处电阻变小, 介质损耗减小, 导致介电值变大。尤其重要的是, 该样品在室温下表现出磁场诱导的巨磁介电效应, 在频率 kHz、外加磁场为1.6×10 6 A/m下, 其值可达5500%, 该巨磁介电效应可能来源于磁电阻效应。采用固相反应法制备了Ho 0.5 Pr 0.5 FeO 3 多晶样品, 对其磁性和磁介电特性进行了系统研究。在 T =4.5 K附近存在Ho离子的反铁磁相变, 在T= 59 ~80K可观测到Fe离子的自旋重取向转变, 磁滞回线表明样品呈现弱铁磁性。在 T = 270 K, 介电常数可达~10 3 , 研究表明该介电常数与270 K附近的电阻变化相关联, 该处电阻变小, 介质损耗减小, 导致介电值变大。尤其重要的是, 该样品在室温下表现出磁场诱导的巨磁介电效应, 在频率 kHz、外加磁场为1.6×10 6 A/m下, 其值可达5500%, 该巨磁介电效应可能来源于磁电阻效应。