@article{meddar_josse_maglione_guiet_la_deniard_decourt_lee_tian_jobic_et al._2012, title={Increasing the Phase-Transition Temperatures in Spin-Frustrated Multiferroic MnWO4 by Mo Doping}, volume={24}, ISSN={["1520-5002"]}, DOI={10.1021/cm2031653}, abstractNote={Ceramic samples of MnW1–xMoxO4 (x ≤ 0.3) solid solution were prepared by a solid-state route with the goal of increasing the magnitude of the spin-exchange couplings among the Mn2+ ions in the spin spiral multiferroic MnWO4. Samples were characterized by X-ray diffraction, optical spectroscopy, magnetization, and dielectric permittivity measurements. It was observed that the Neel temperature TN, the spin spiral ordering temperature TM2, and the ferroelectric phase-transition temperature TFE2 of MnWO4 increased upon the nonmagnetic substitution of Mo6+ for W6+. Like pure MnWO4, the ferroelectric critical temperature TFE2(x) coincides with the magnetic ordering temperature TM2(x). A density functional analysis of the spin-exchange interactions for a hypothetical MnMoO4 that is isostructural with MnWO4 suggests that Mo substitution increases the strength of the spin-exchange couplings among Mn2+ in the vicinity of a Mo6+ ion. Our study shows that the Mo-doped MnW1–xMoxO4 (x ≤ 0.3) compounds are spin-frustrat...}, number={2}, journal={CHEMISTRY OF MATERIALS}, author={Meddar, Lynda and Josse, Michael and Maglione, Mario and Guiet, Amandine and La, Carole and Deniard, Philippe and Decourt, Rodolphe and Lee, Changhoon and Tian, Chuan and Jobic, Stephane and et al.}, year={2012}, month={Jan}, pages={353–360} }
 @article{tian_wibowo_loye_whangbo_2011, title={On the Magnetic Insulating States, Spin Frustration, and Dominant Spin Exchange of the Ordered Double-Perovskites Sr2CuOsO6 and Sr2NiOsO6: Density Functional Analysis}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic200167j}, abstractNote={The ordered double-perovskites Sr(2)MOsO(6) (M = Cu, Ni) consisting of 3d and 5d transition-metal magnetic ions (M(2+) and Os(6+), respectively) are magnetic insulators; the magnetic susceptibilities of Sr(2)CuOsO(6) and Sr(2)NiOsO(6) obey the Curie-Weiss law with dominant antiferromagnetic and ferromagnetic interactions, respectively, and the zero-field-cooled and field-cooled susceptibility curves of both compounds diverge below ∼20 K. In contrast, the available density functional studies predicted both Sr(2)CuOsO(6) and Sr(2)NiOsO(6) to be metals. We resolved this discrepancy on the basis of systematic density functional calculations. The magnetic insulating states of Sr(2)MOsO(6) are found only when a substantially large on-site repulsion is employed for the Os atom, although it is a 5d element. The cause for the divergence between the zero-field-cooled and field-cooled susceptibility curves in both compounds and the reason for the difference in their dominant magnetic interactions were investigated by examining their spin exchange interactions.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Wibowo, Arief C. and Loye, Hans-Conrad Zur and Whangbo, Myung-Hwan}, year={2011}, month={May}, pages={4142–4148} }
 @article{tian_lee_kan_wu_whangbo_2010, title={Analysis of the Magnetic Structure and Ferroelectric Polarization of Monoclinic MnSb2S4 by Density Functional Theory Calculations}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101351b}, abstractNote={Monoclinic MnSb(2)S(4) consists of MnS(4) chains made up of edge-sharing MnS(6) octahedra and adopts a (0, 0.369, 0) magnetic superstructure below 25 K. This ordered magnetic structure, in which the spins of each MnS(4) chain possess a helical spin arrangement, has C(2)' symmetry. On the basis of density functional theory calculations, we explored the origin of the observed noncollinear spin arrangement of MnSb(2)S(4) by evaluating its spin exchanges to find that spin exchanges are frustrated not only within each MnS(4) chain but also between adjacent MnS(4) chains. Our analysis predicts that MnSb(2)S(4) is a multiferroic with a ferroelectric polarization of ∼14 μC/m(2) along the chain direction, and a field-induced reversal of the ferroelectric polarization of MnSb(2)S(4) can occur by reversing the direction of the helical spin rotation in each MnS(4) chain.}, number={23}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Lee, Changhoon and Kan, Erjun and Wu, Fang and Whangbo, Myung-Hwan}, year={2010}, month={Dec}, pages={10956–10959} }
 @article{kan_xiang_wu_tian_lee_yang_whangbo_2010, title={Prediction for room-temperature half-metallic ferromagnetism in the half-fluorinated single layers of BN and ZnO}, volume={97}, number={12}, journal={Applied Physics Letters}, author={Kan, E. J. and Xiang, H. J. and Wu, F. and Tian, C. and Lee, C. and Yang, J. L. and Whangbo, M. H.}, year={2010} }
 @article{wu_kan_tian_whangbo_2010, title={Theoretical Analysis of the Spin Exchange and Magnetic Dipole-Dipole Interactions Leading to the Magnetic Structure of Ni3TeO6}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101022f}, abstractNote={The origin of the collinear antiferromagnetic magnetic structure of Ni(3)TeO(6) below 52 K was analyzed by calculating its spin exchanges on the basis of density functional calculations, and the cause for the parallelc-spin orientation found for this magnetic structure by calculating the spin-orbit coupling and magnetic dipole-dipole interaction energies. The calculated exchanges correctly predict the observed magnetic structure below 52 K, and lead practically to no spin frustration. The perpendicularc- and parallelc-spin orientations are predicted by the spin-orbit coupling and the magnetic dipole-dipole interactions, respectively. However, the magnetic dipole-dipole interactions are stronger than the spin-orbit coupling interactions, and hence are responsible for the spin orientation observed for Ni(3)TeO(6).}, number={16}, journal={INORGANIC CHEMISTRY}, author={Wu, Fang and Kan, Erjun and Tian, Chuan and Whangbo, Myung-Hwan}, year={2010}, month={Aug}, pages={7545–7548} }
 @article{tian_kan_lee_whangbo_2010, title={pi-Back-Donation Effect of the Cyanide Ligands on the Electron Correlation and Charge Transfer in Prussian Blue RbMn[Fe(CN)(6)]}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic902577r}, abstractNote={The temperature-induced charge transfer between the Mn and Fe sites in RbMn[Fe(CN)(6)] was analyzed by density functional theory calculations. Our analysis indicates that the extent of electron correlation (equivalently, the pairing energy or the on-site repulsion) is much greater for the Mn(n+) ion than for the Fe(n+) ion (n = 2, 3). This surprising and counterintuitive finding is a consequence of the pi-back-donation effect of the CN ligands.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Kan, Erjun and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2010}, month={Apr}, pages={3086–3088} }
 @article{tian_lee_xiang_zhang_payen_jobic_whangbo_2009, title={Magnetic structure and ferroelectric polarization of MnWO4 investigated by density functional calculations and classical spin analysis}, volume={80}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.80.104426}, abstractNote={The ordered magnetic states of MnWO4 at low temperatures were examined by evaluating the spin exchange interactions between the Mn2+ ions of MnWO4 on the basis of first principles density functional calculations and by performing classical spin analysis with the resulting spin exchange parameters. Our work shows that the spin exchange interactions are frustrated within each zigzag chain of Mn2+ ions along the c direction and between such chains of Mn2+ ions along the a direction. This explains the occurrence of a spiral-spin order along the c and a directions in the incommensurate magnetic state AF2, and that of a up arrow up arrow down arrow down arrow spin order along the c and a directions in the commensurate magnetic state AF1. The ferroelectric polarization of MnWO4 in the spiral-spin state AF2 was examined by performing Berry phase calculations for a model superstructure to find that the ferroelectric polarization occurs along the b direction, in agreement with experiment.}, number={10}, journal={PHYSICAL REVIEW B}, author={Tian, Chuan and Lee, Changhoon and Xiang, Hongjun and Zhang, Yuemei and Payen, Christophe and Jobic, Stephane and Whangbo, Myung-Hwan}, year={2009}, month={Sep} }