Horsch Peter, Khaliullin Giniyat, Oleś Andrzej M
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Phys Rev Lett. 2003 Dec 19;91(25):257203. doi: 10.1103/PhysRevLett.91.257203. Epub 2003 Dec 16.
We use exact diagonalization combined with mean-field theory to investigate the phase diagram of the spin-orbital model for cubic vanadates. The spin-orbit coupling competes with Hund's exchange and triggers a novel phase, with the ordering of t(2g) orbital magnetic moments stabilized by the tilting of VO6 octahedra. It explains qualitatively spin canting and reduction of magnetization observed in YVO3. At finite temperature, an orbital instability in the C-type antiferromagnetic phase induces modulation of magnetic exchange constants even in the absence of lattice distortions. The calculated spin structure factor shows a magnon splitting at q-->=(0,0,pi / 2) due to the orbital dimerization.
我们运用精确对角化结合平均场理论来研究立方钒酸盐的自旋 - 轨道模型的相图。自旋 - 轨道耦合与洪德交换相互竞争，并引发了一个新的相，其中t(2g)轨道磁矩的有序排列通过VO6八面体的倾斜得以稳定。这定性地解释了在YVO3中观察到的自旋倾斜和磁化强度降低现象。在有限温度下，即使在没有晶格畸变的情况下，C型反铁磁相中的轨道不稳定性也会导致磁交换常数的调制。计算得到的自旋结构因子显示，由于轨道二聚化，在q = (0, 0, π / 2)处出现了磁振子分裂。
