几何阻挫反铁磁体CdCr₂O₄中非公度自旋序的静力学与动力学
Statics and dynamics of incommensurate spin order in a geometrically frustrated antiferromagnet CdCr2O4.
作者信息
Chung J-H, Matsuda M, Lee S-H, Kakurai K, Ueda H, Sato T J, Takagi H, Hong K-P, Park S
机构信息
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8552, USA.
出版信息
Phys Rev Lett. 2005 Dec 9;95(24):247204. doi: 10.1103/PhysRevLett.95.247204. Epub 2005 Dec 8.
Using elastic and inelastic neutron scattering we show that a cubic spinel, CdCr2O4, undergoes an elongation along the c axis (c > a = b) at its spin-Peierls-like phase transition at T(N) = 7.8 K. The Néel phase (T < T(N)) has an incommensurate spin structure with a characteristic wave vector Q(M) = (0, delta,1) with delta approximately 0.09 and with spins lying on the ac plane. This is in stark contrast to another well-known Cr-based spinel, ZnCr2O4, that undergoes a c-axis contraction and a commensurate spin order. The magnetic excitation of the incommensurate Néel state has a weak anisotropy gap of 0.6 meV and it consists of at least three bands extending up to 5 meV.
利用弹性和非弹性中子散射，我们表明立方尖晶石CdCr2O4在其T(N)=7.8 K的类自旋-派尔斯相变时沿c轴（c > a = b）发生伸长。奈尔相（T < T(N)）具有非公度自旋结构，其特征波矢Q(M) = (0, δ, 1)，其中δ约为0.09，且自旋位于ac平面上。这与另一种著名的基于Cr的尖晶石ZnCr2O4形成鲜明对比，后者发生c轴收缩和公度自旋序。非公度奈尔态的磁激发具有0.6 meV的弱各向异性能隙，并且它由至少三个延伸至5 meV的能带组成。
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