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研究了Sr_2Fe_(1-x)Al_xMoO_6(0≤x≤0·30)系列多晶样品的磁学和输运性质.室温X射线衍射谱图的精修结果显示Al~(3+)掺杂没有改变样品的晶格结构,但提高了Sr_2FeMoO_6晶格的阳离子有序度.5K时样品的磁化曲线说明平均单位分子饱和磁矩随着Al含量的增加而下降,但平均单位Fe离子磁矩却逐渐提高.磁化曲线的拟合结果显示样品内反铁磁相互作用对饱和磁矩的贡献随着Al含量的增加而下降,说明一定量的Fe离子被Al替代后,抑制了样品内Fe—O—Fe反相边界的形成,从而提高了Sr_2FeMoO_6晶格的阳离子有序度和平均单位Fe离子磁矩.对饱和磁矩的分析表明非磁性Al~(3+)离子掺杂会形成无磁相互作用的Mo—O—Al—O—Mo区,可以将原来较大的Mo—O—Fe亚铁磁区分割成许多小的区域,并且使这些亚铁磁区间的磁耦合作用变弱,从而提高了低场磁电阻效应.阳离子有序度的提高使来源于自旋相关电子在反相边界处散射的高场磁电阻明显降低,导致了样品的磁电阻在x=0·15时达到了最大值.
The magnetic and transport properties of Sr2Fe1 (1-x) Al_xMoO_6 (0≤x≤0.30) polycrystalline samples were investigated.The results of X-ray diffraction at room temperature showed that there was no Al 3+ doping However, the lattice order of the Sr 2 FeMoO 6 crystal is changed, and the magnetization curve of the sample at 5 K shows that the saturation moment of average unit molecule decreases with the increase of Al content, but the average unit Fe ion magnetic moment gradually The results of fitting of the magnetization curves show that the contribution of the antiferromagnetic interaction in the sample to the saturation magnetization decreases with the increase of the Al content, indicating that the Fe-O- Fe anti-phase boundary formation, thereby increasing the order of Sr2FeMoO6 lattice and the average unit of Fe ion magnetic moment. Analysis of the saturation moment shows that non-magnetic Al ~ (3 +) ion doping will form a non-magnetic interaction Mo-O-Al-O-Mo region, the originally large ferromagnetic region of Mo-O-Fe is segmented into many small regions and the magnetic coupling between these ferrimagnetic regions is weakened to increase Low-field magnetoresistance effect. The increase in the degree of cation order results from the spin-dependent charge The magnetic field resistance of the high-field scattering at the opposite boundary is significantly reduced, resulting in the maximum magnetoresistance of the sample at x = 0.15.