The magnetic and dielectric properties of multiferroic Sr- substituted Zn2-Y hexagonal ferrites

The magnetic and dielectric properties of Sr-substituted Zn2-Y hexagonal ferrites （Ba2-x SrxZn2Fe12O22, 1.0 〈 x ≤ 1.5） are studied in this paper. Sr substitution will lead to the variation of cation occupation, which influences both the magnetic and electric properties. As Sr content x rises from 1.0 to 1.5, magnetic hysteresis loop gets wider gradually and the permeability drops rapidly due to the transformation from ferrimagnetic to antiferromagnetic phase. Moreover, permittivity rises with increasing Sr content. Under a certain external magnetic field, the phase transition of helical spin structure of Ba0.5Srl.5Zn2Fe12O22 at about 295 K seems to open a possibility for the room-temperature ferroelectricity induced by magnetic field. But its low resistivity prevents the observation of ferroelectric and magnetoelectric properties at room-temperature.     

基于铁氧体基板的开口谐振环的可调微波左手特性研究

利用铁氧体的外场调制特性，提出采用铁氧体作为金属环线结构的介质基板，实现频率可调左手材料. 首先采用时域差分有限元方法数值模拟了基板材料参数变化的条件下，开口谐振环的频率可调性规律. 随基板材料的介电常数或磁导率升高，与开口谐振环负磁导率对应的透射谷频率将显著降低. 实验制备了一系列超高频软磁六角铁氧体，利用外加磁场有效调制了其磁导率. 并通过实验表明，通过调控外加磁场可以有效地调控开口谐振环负磁导率对应的透射谷频率. 关键词： 左手材料 开口谐振环 铁氧体 可调