High Pressure Crystal and Magnetic Phase Transitions in Multiferroic Bi0.9La0.1FeO3
High Pressure Crystal and Magnetic Phase Transitions in Multiferroic Bi0.9La0.1FeO3
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DOI：
10.1021/cm403558j
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发表时间：
2014-01
影响因子：
8.6
通讯作者：
C. Knee;M. Tucker;P. Manuel;S. Cai;J. Bielecki;L. Börjesson;S. Eriksson
中科院分区：
文献类型：
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作者：
C. Knee;M. Tucker;P. Manuel;S. Cai;J. Bielecki;L. Börjesson;S. Eriksson
用高分辨中子粉末衍射方法研究了多铁性Bi_（0.9）La_（0.1）FeO_3的晶体结构和磁结构。观察到两个结构相变。第一种是在近似1GPa的压力下，将极性R3 c结构转变为反极性PbZrO 3类根2a（p）x2根2a（p）x2 a（p）钙钛矿超结构;第二个，在类似于5GPa下，导致较小的根2a（p）×根2a（p）× 2a（p）晶胞和用Ibmm描述的结构（Imma的非标准设置）对称性，其中a（-）a（-）B（0）八面体倾斜系统被保留并且反极性阳离子位移丢失。伴随着核结构的变化，反铁磁自旋结构从具有调制长度（λ近似为770埃）的摆线演变为具有沿正交晶胞的b轴（Pbam）和a轴（Ibmm）排列的沿着的矩的共线排列。与BiFeO 3相比，从菱面体到正交结构的转变被抑制了类似于3 GPa，反映了镧对立体化学活性铋孤对电子的稀释。本文测定了Bi_（1-x）La_xFeO_3（0.0 ≤ x ≤ 0.3）在化学压力和流体静压作用下的晶胞收缩之间的关系，La的取代量为1mol%时约相当于施加0.05GPa。发现Bi0.9La0.1FeO3具有比BiFeO 3更高的体积模量。
The crystal and magnetic structures of multiferroic Bi0.9La0.1FeO3 have been studied using high resolution neutron powder diffraction in the pressure range 0-8 GPa. Two structural phase transitions are observed. The first, at similar to 1 GPa, transforms the polar R3c structure to an antipolar PbZrO3-like root 2a(p) x 2 root 2a(p) x 2a(p) perovskite superstructure; the second, at similar to 5 GPa, results in a smaller, root 2a(p) x root 2a(p) x 2a(p) unit cell and a structure described with Ibmm (nonstandard setting of Imma) symmetry, in which the a(-)a(-)b(0) octahedral tilt system is retained and the antipolar cation displacements lost. Accompanying the changes in the nuclear structure, the antiferromagnetic spin structure evolves from a cycloid, with a modulation length, lambda approximate to 770 angstrom, to collinear arrangements with the moments aligned along the b-axis (Pbam) and the a-axis (Ibmm) of the orthorhombic unit cells. In comparison with BiFeO3 the transition from a rhombohedral to an orthorhombic structure is suppressed by similar to 3 GPa, reflecting the dilution of the stereochemically active bismuth lone pair by lanthanum. A correlation between the cell contraction of Bi1-xLaxFeO3 (0.0 <= x <= 0.3) induced by chemical pressure and hydrostatic pressure on BiFeO3 is determined, with substitution of 1 mol % of La approximately equivalent to application of 0.05 GPa. Bi0.9La0.1FeO3 is found to have a higher bulk modulus than BiFeO3.