@article{whangbo_xiang_koo_gordon_whitten_2019, title={Electronic and Structural Factors Controlling the Spin Orientations of Magnetic Ions}, volume={58}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/acs.inorgchem.9b00687}, DOI={10.1021/acs.inorgchem.9b00687}, abstractNote={Magnetic ions M in discrete molecules and extended solids form ML n complexes with their first-coordinate ligand atoms L. The spin moment of M in a complex ML n prefers a certain direction in coordinate space because of spin-orbit coupling (SOC). In this minireview, we examine the structural and electronic factors governing the preferred spin orientations. Elaborate experimental measurements and/or sophisticated computational efforts are required to find the preferred spin orientations of magnetic ions, largely because the energy scale of SOC is very small. The latter is also the very reason why one can readily predict the preferred spin orientation of M by analyzing the SOC-induced highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) interactions of the ML n complexes in terms of qualitative perturbation theory. The strength of this HOMO-LUMO interaction depends on the spin orientation, which is governed by the selection rules based on the minimum |Δ L z| value (i.e., the minimum difference in the magnetic quantum numbers) between the HOMO and LUMO. With the local z axis of ML n chosen as its n-fold rotational axis, the preferred spin orientation is parallel to the z axis (∥ z) when |Δ L z| = 0 but perpendicular to the z axis (⊥ z) when |Δ L z| = 1.}, number={18}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Whangbo, Myung-Hwan and Xiang, Hongjun and Koo, Hyun-Joo and Gordon, Elijah E. and Whitten, Jerry L.}, year={2019}, month={Jun}, pages={11854–11874} }
 @article{kan_xiang_wu_lee_yang_whangbo_2010, title={Ferrimagnetism in zigzag graphene nanoribbons induced by main-group adatoms}, volume={96}, number={10}, journal={Applied Physics Letters}, author={Kan, E. and Xiang, H. J. and Wu, F. and Lee, C. and Yang, J. L. and Whangbo, M. H.}, year={2010} }
 @article{dai_xiang_whangbo_2008, title={Effects of spin-orbit coupling on magnetic properties of discrete and extended magnetic systems}, volume={29}, ISSN={["0192-8651"]}, DOI={10.1002/jcc.21011}, abstractNote={Abstract}, number={13}, journal={JOURNAL OF COMPUTATIONAL CHEMISTRY}, author={Dai, Dadi and Xiang, Hongjun and Whangbo, Myung-Hwan}, year={2008}, month={Oct}, pages={2187–2209} }
 @article{xiang_wei_whangbo_2008, title={Origin of the structural and magnetic anomalies of the layered compound SrFeO2: A density functional investigation}, volume={100}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.100.167207}, abstractNote={The structural and magnetic anomaly of the layered compound SrFeO2 are examined by first-principles density functional calculations and Monte Carlo simulations. The down-spin Fe 3d electron occupies the d(z(2)) level rather than the degenerate (d(xz), d(yz)) levels, which explains the absence of a Jahn-Teller instability, the easy ab-plane magnetic anisotropy, and the observed three-dimensional (0.5, 0.5, 0.5) antiferromagnetic order. Monte Carlo simulations show that the strong interlayer spin exchange is essential for the high Néel temperature.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Wei, Su-Huai and Whangbo, M. -H.}, year={2008}, month={Apr} }
 @article{xiang_lee_whangbo_2007, title={Absence of a spiral magnetic order in Li2CuO2 containing one-dimensional CuO2 ribbon chains}, volume={76}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.76.220411}, abstractNote={On the basis of first principles density functional theory electronic structure calculations as well as classical spin analysis, we explored why the magnetic oxide Li2CuO2, consisting of CuO2 ribbon chains made up of edge-sharing CuO4 squares, does not exhibit a spiral-magnetic order. Our work shows that, due to the next-nearest-neighbor interchain interactions, the observed collinear magnetic structure becomes only slightly less stable than the spin-spiral ground state, and many states become nearly degenerate in energy with the observed collinear structure. This suggests that the collinear magnetic structure of Li2CuO2 is a consequence of order-by-disorder induced by next-nearest-neighbor interchain interactions.}, number={22}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Lee, C. and Whangbo, M. -H.}, year={2007}, month={Dec} }
 @article{xiang_whangbo_2007, title={Charge order and the origin of giant magnetocapacitance in LuFe2O4}, volume={98}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.98.246403}, abstractNote={The nature of the charge order in the charge frustrated compound LuFe(2)O(4) and its effect on magnetocapacitance were examined on the basis of first-principles electronic structure calculations and Monte Carlo simulations of electrostatic energy. Our work shows that two different types of charge order of almost equal stability (i.e., square root of 3 x square root of 3 and chain types) occur in the Fe(2)O(4) layers of LuFe(2)O(4), and that the ground state of LuFe(2)O(4) has a ferrielectric arrangement of the Fe(2)O(4) layers with square root of 3 x square root of 3 charge order. The giant magnetocapacitance effect of LuFe(2)O(4) at room temperature is accounted for in terms of charge fluctuations arising from the interconversion between the two types of charge order, that becomes hindered by an applied magnetic field.}, number={24}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Whangbo, M.-H.}, year={2007}, month={Jun} }
 @article{angst_khalifah_hermann_xiang_whangbo_varadarajan_brill_sales_mandrus_2007, title={Charge order superstructure with integer iron valence in Fe2OBO3}, volume={99}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.99.086403}, abstractNote={Solution-grown single crystals of Fe(2)OBO(3) were characterized by specific heat, Mössbauer spectroscopy, and x-ray diffraction. A peak in the specific heat at 340 K indicates the onset of charge order. Evidence for a doubling of the unit cell at low temperature is presented. Combining structural refinement of diffraction data and Mössbauer spectra, domains with diagonal charge order are established. Bond-valence-sum analysis indicates integer valence states of the Fe ions in the charge ordered phase, suggesting Fe(2)OBO(3) is the clearest example of ionic charge order so far.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Angst, M. and Khalifah, P. and Hermann, R. P. and Xiang, H. J. and Whangbo, M.-H. and Varadarajan, V. and Brill, J. W. and Sales, B. C. and Mandrus, D.}, year={2007}, month={Aug} }
 @article{xiang_whangbo_2007, title={Cooperative effect of electron correlation and spin-orbit coupling on the electronic and magnetic properties of Ba2NaOsO6}, volume={75}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.75.052407}, abstractNote={The electronic and magnetic properties of the cubic double perovskite ${\mathrm{Ba}}_{2}\mathrm{Na}\mathrm{Os}{\mathrm{O}}_{6}$ were examined by performing first-principles density functional theory calculations and analyzing spin-orbit coupled states of an ${\mathrm{Os}}^{7+}$ $({d}^{1})$ ion at an octahedral crystal field. The insulating behavior of ${\mathrm{Ba}}_{2}\mathrm{Na}\mathrm{Os}{\mathrm{O}}_{6}$ was shown to originate from a cooperative effect of electron correlation and spin-orbit coupling. This cooperative effect is responsible not only for the absence of orbital ordering in ${\mathrm{Ba}}_{2}\mathrm{Na}\mathrm{Os}{\mathrm{O}}_{6}$ but also for a small magnetic moment and a weak magnetic anisotropy in ${\mathrm{Ba}}_{2}\mathrm{Na}\mathrm{Os}{\mathrm{O}}_{6}$.}, number={5}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Whangbo, M. -H.}, year={2007}, month={Feb} }
 @article{xiang_whangbo_2007, title={Density-functional characterization of the multiferroicity in spin spiral chain cuprates}, volume={99}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.99.257203}, abstractNote={The ferroelectricity of the spiral magnets LiCu2O2 and LiCuVO4 was examined by calculating the electric polarizations of their spin spiral states on the basis of density-functional theory with spin-orbit coupling. Our work unambiguously reveals that spin-orbit coupling is responsible for the ferroelectricity with the primary contribution from the spin-orbit coupling on the Cu sites, but the asymmetric density distribution responsible for the electric polarization occurs mainly around the O atoms. The electric polarization is calculated to be much greater for the ab-plane than for the bc-plane spin spiral. The observed spin-spiral plane is found to be consistent with the observed direction of the electric polarization for LiCuVO4, but inconsistent for LiCu2O2.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Whangbo, M. -H.}, year={2007}, month={Dec} }
 @article{angst_hermann_schweika_kim_khalifah_xiang_whangbo_kim_sales_mandrus_2007, title={Incommensurate charge order phase in Fe2OBO3 due to geometrical frustration}, volume={99}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.99.256402}, abstractNote={The temperature dependence of charge order in Fe2OBO3 was investigated by resistivity and differential scanning calorimetry measurements, Mössbauer spectroscopy, and synchrotron x-ray scattering, revealing an intermediate phase between room temperature and 340 K, characterized by coexisting mobile and immobile carriers, and by incommensurate superstructure modulations with temperature-dependent propagation vector (1/2, 0, tau). The incommensurate modulations arise from specific antiphase boundaries with low energy cost due to geometrical charge frustration.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Angst, M. and Hermann, R. P. and Schweika, W. and Kim, J. -W. and Khalifah, P. and Xiang, H. J. and Whangbo, M. -H. and Kim, D. -H. and Sales, B. C. and Mandrus, D.}, year={2007}, month={Dec} }
 @article{xiang_singh_2007, title={Suppression of thermopower of NaxCoO2 by an external magnetic field: Boltzmann transport combined with spin-polarized density functional theory}, volume={76}, number={19}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Xiang, H. J. and Singh, D. J.}, year={2007} }