Magnetic excitations and orbital physics in the ferrimagnetic spinels Mn B2 O4 (B=Mn,V)
Magnetic excitations and orbital physics in the ferrimagnetic spinels Mn B2 O4 (B=Mn,V)
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DOI：
10.1103/physrevb.77.054412
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发表时间：
2008-02
影响因子：
3.7
通讯作者：
J-H. Chung;J. Kim;Seungh-Hun Lee;Taku J. Sato;T. Suzuki;M. Katsumura;T. Katsufuji
中科院分区：
文献类型：
--
作者：
J-H. Chung;J. Kim;Seungh-Hun Lee;Taku J. Sato;T. Suzuki;M. Katsumura;T. Katsufuji
Using neutron scattering techniques, we have investigated spin wave excitations in noncollinear ferrimagnetic spinels $\mathrm{Mn}{B}_{2}{\mathrm{O}}_{4}$ $(B=\mathrm{Mn},\mathrm{V})$ with ${e}_{g}$ and ${t}_{2g}$ orbital degeneracies, respectively, that lead to tetragonal distortions along opposite directions. Linear spin wave analysis of the excitations yields spatially inhomogeneous nearest neighbor interactions in both tetragonal spinels. We find the ratio ${J}^{c}∕{J}^{ab}\ensuremath{\approx}\ensuremath{-}0.06(4)$ for ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ $(cga=b)$ and $\ensuremath{\approx}0.3(1)$ for $\mathrm{Mn}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$ $(cla=b)$. Resulting exchange couplings of ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ can be qualitatively explained in terms of possible overlaps of ${t}_{2g}$ and ${e}_{g}$ electrons of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$ ions. On the other hand, those of $\mathrm{Mn}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$, in particular, the strong ${J}^{c}$, seem to contradict with the antiferro-orbital state of ${\mathrm{V}}^{3+}$ $({t}_{2g}^{2})$ ions that was proposed by a recent synchrotron x-ray study [T. Suzuki et al., Phys. Rev. Lett. 98, 127203 (2007)]. Theoretical implications to the orbital physics are also discussed.
Using neutron scattering techniques, we have investigated spin wave excitations in noncollinear ferrimagnetic spinels $\mathrm{Mn}{B}_{2}{\mathrm{O}}_{4}$ $(B=\mathrm{Mn},\mathrm{V})$ with ${e}_{g}$ and ${t}_{2g}$ orbital degeneracies, respectively, that lead to tetragonal distortions along opposite directions. Linear spin wave analysis of the excitations yields spatially inhomogeneous nearest neighbor interactions in both tetragonal spinels. We find the ratio ${J}^{c}∕{J}^{ab}\ensuremath{\approx}\ensuremath{-}0.06(4)$ for ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ $(cga=b)$ and $\ensuremath{\approx}0.3(1)$ for $\mathrm{Mn}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$ $(cla=b)$. Resulting exchange couplings of ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ can be qualitatively explained in terms of possible overlaps of ${t}_{2g}$ and ${e}_{g}$ electrons of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$ ions. On the other hand, those of $\mathrm{Mn}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$, in particular, the strong ${J}^{c}$, seem to contradict with the antiferro-orbital state of ${\mathrm{V}}^{3+}$ $({t}_{2g}^{2})$ ions that was proposed by a recent synchrotron x-ray study [T. Suzuki et al., Phys. Rev. Lett. 98, 127203 (2007)]. Theoretical implications to the orbital physics are also discussed.