双钙钛矿化合物Sr_2Mn_(1-x)Ga_xMoO_6(x=0,0.1,0.2,0.3)的晶体结构与磁性  

Crystal structure and magnetic properties characterization of double-perovskite compounds Sr_2Ga_(1-x)Mn_xMoO_6(x=0,0.1,0.2,0.3)

作　　者：彭文彪[1] 罗道源[1] 郭光华[1] 

机构地区：[1]中南大学物理科学与技术学院,长沙410083

出　　处：《粉末冶金材料科学与工程》2012年第3期291-296,共6页Materials Science and Engineering of Powder Metallurgy

基　　金：国家自然科学基金资助项目(60571043);湖南省科技计划资助项目(2011FJ3193)

摘　　要：用非磁性Ga3+部分替代Sr2MnMoO6中的Mn2+,获得Sr2Mn1-xGaxMoO6(x=0,0.1,0.2,0.3)多晶样品,通过X射线衍射(XRD)分析和磁性能测量研究Ga3+对晶体结构和磁性的影响。XRD谱Rietveld结构精修分析表明,Sr2Ga1-xMnxMoO6具有四方对称晶体结构(空间群I4/m)。随着Ga含量增加,B/B-原子占位有序度降低,<Mn—O>平均键长减小,而<Mo—O>平均键长增大,<Mn—O1—Mo>平均键角保持180o不变,<Mn—O2—Mo>平均键角逐渐扩张。5 K及300 K温度下,样品均为反铁磁体,但低掺杂样品在低温(5 K)下表现出微弱的铁磁性。上述结果表明,Ga3+对Mn2+的电子掺杂引起部分Mo离子价态由+6价转变为+5价。Polycrystalline Sr_2Mn_（1-x）Ga_xMoO_6（x=0,0.1,0.2,0.3） compounds were obtained through using nonmagnetic Ga3＋ to instead of Mn2＋ in Sr2MnMoO6. The effect of Ga3＋ on the structure and magnetic properties of Sr2MnMoO6 was studied by means of XRD and magnetization measurements. Rieveld refinement results of XRD show that the Sr2Ga（1-x）MnxMoO6 （x=0, 0.1, 0.2, 0.3） series of compounds crystallize in tetragonal symmetry （space group 14/m）. With the increasing of Ga3＋ doping, the degree of B/B＇ cation order decreases, a shrink of the average 〈Mn--O〉 bond distance and an enlargement of the average 〈Mo--O〉 bond distance are found, the average 〈Mn--O1--Mo〉 bond angles of 180° are not changed and the average 〈Mn--O2--Mo〉 bond angle sightly increases. The magnetic measurements in 5 K and 300 K suggest that these compounds are antiferromagnetism, and at low temperature （5 K） these low-doped compounds show weak ferromagnetic properties. These results show that the election doping of Ga3＋ to Mn2＋ can cause the change of the ionic valence from Mo5＋ to Mo6＋.

关 键 词：双钙钛矿 结构精修 晶体结构 磁性 

分 类 号：O469[理学—凝聚态物理]