X-ray resonant scattering study of the incommensurate charge-orbital density wave in La 2-2 x Sr 1+2 x Mn 2 O 7 ( x = 0.7)
X-ray resonant scattering study of the incommensurate charge-orbital density wave in La 2-2 x Sr 1+2 x Mn 2 O 7 ( x = 0.7)
复制标题
La 2-2 x Sr 1 2 x Mn 2 O 7 ( x = 0.7)中不相称电荷轨道密度波的X射线共振散射研究
DOI：
10.1088/1742-6596/211/1/012006
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Beale T
中科院分区：
文献类型：
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作者：
Beale T
半个多世纪以来，人们一直在理论上提出轨道序，随后在大量材料中观察到了轨道序。电荷有序化通常伴随着从金属到绝缘体的转变。在锰氧化物中，庞磁电阻（CMR）与电荷和轨道反铁磁绝缘相和铁磁金属相之间的竞争有关。在锰氧化物的电荷和轨道顺序的初始模型集中在棋盘电荷顺序结构，在许多半掺杂系统中观察到。通过共振X射线散射观察超晶格反射，发现La{sub 0.6}Sr{sub 2.4}Mn{sub 2}O{sub 7}中存在无公度电荷有序和结构畸变。这种结构的扭曲是伴随的轨道秩序的指示，导致我们的建议，一个不相称的电荷轨道密度波。观察到超晶格结构畸变反射与调制矢量（0.178，0.178，0），和电荷阶反射与调制矢量（0.356，0.356，0）。在半掺杂双层锰氧化物中观察到的低温电荷序熔化，由于没有长程磁序而不存在。
Orbital order has been proposed theoretically for more than half a century, and has subsequently been observed in a huge range of materials. Charge ordering is generally accompanied by a transition from a metal to an insulator. In manganites, colossal magneto-resistance (CMR) is associated with competition between charge and orbital antiferromagnetic insulating phases and ferromagnetic metallic phases. Initial models of charge and orbital order in the manganites concentrated on the chequerboard charge order structure, observed in many half doped systems. Incommensurate charge ordering and structural distortions have been identified in La{sub 0.6}Sr{sub 2.4}Mn{sub 2}O{sub 7} through the observation of superlattice reflections using resonant x-ray scattering. Such structural distortions are indicative of concomitant orbital order, leading to our proposal of an incommensurate charge-orbital density wave. Superlattice structural distortion reflections were observed with a modulation vector (0.178, 0.178, 0), and charge order reflections with a modulation vector (0.356, 0.356, 0). Low temperature charge order melting, observed in the half doped bilayer manganite, is not present due to the absence of long range magnetic order.