@article{lee_kang_hong_shim_whangbo_2014, title={Analysis of the Difference between the Pyroxenes LiFeSi2O6 and LiFeGe2O6 in Their Spin Order, Spin Orientation, and Ferrotoroidal Order}, volume={26}, ISSN={["1520-5002"]}, DOI={10.1021/cm5001413}, abstractNote={The pyroxenes LiFeSi2O6 and LiFeGe2O6 are isostructural and isoelectronic, but they differ in their spin order, spin orientation and ferrotoroidal order. The reasons for these differences were probed by density functional theory electronic structure calculations and magnetic dipole–dipole (MDD) interaction energy calculations. The ferromagnetic Fe-zigzag chains of LiFeSi2O6 arise from the antiferromagnetic interchain spin exchanges and the antiferromagnetic Fe-zigzag chains of LiFeGe2O6 from the antiferromagnetic intrachain spin exchange. The preferred spin orientations of LiFeGe2O6 and LiFeSi2O6 are not caused by spin–orbit coupling but by MDD interactions. LiFeSi2O6 undergoes a ferrotoroidal order because it has spin exchange rings made up of an even number of antiferromagnetic spin exchanges paths with comparable strengths. A ferrotoroidal order is not expected for LiFeGe2O6 because it has no such spin exchange rings.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Kang, Jinhee and Hong, Jisook and Shim, Ji Hoon and Whangbo, Myung-Hwan}, year={2014}, month={Feb}, pages={1745–1750} }
 @article{lapidus_manson_park_clement_ghannadzadeh_goddard_lancaster_moeller_blundell_telling_et al._2013, title={Antiferromagnetic ordering through a hydrogen-bonded network in the molecular solid CuF2(H2O)(2)(3-chloropyridine)}, volume={49}, ISSN={["1359-7345"]}, DOI={10.1039/c2cc37444g}, abstractNote={CuF(2)(H(2)O)(2)(3-chloropyridine) possesses a five-coordinate Cu(2+) center with a slightly distorted trigonal bypyramidal coordination geometry. Strong intermolecular F···H-O hydrogen bonds enable the formation of 2D layers and provide the primary magnetic exchange path that leads to the stabilization of long-range antiferromagnetic (AFM) order below T(N) = 2.1 K.}, number={5}, journal={CHEMICAL COMMUNICATIONS}, author={Lapidus, Saul H. and Manson, Jamie L. and Park, Hyunsoo and Clement, Alexander J. and Ghannadzadeh, Saman and Goddard, Paul and Lancaster, Tom and Moeller, Johannes S. and Blundell, Stephen J. and Telling, Mark T. F. and et al.}, year={2013}, pages={499–501} }
 @article{schlueter_park_halder_armand_dunmars_chapman_manson_singleton_mcdonald_plonczak_et al._2012, title={Importance of Halogen center dot center dot center dot Halogen Contacts for the Structural and Magnetic Properties of CuX2(pyrazine-N,N '-dioxide)(H2O)(2) (X = Cl and Br)}, volume={51}, number={4}, journal={Inorganic Chemistry}, author={Schlueter, J. A. and Park, H. and Halder, G. J. and Armand, W. R. and Dunmars, C. and Chapman, K. W. and Manson, J. L. and Singleton, J. and McDonald, R. and Plonczak, A. and et al.}, year={2012}, pages={2121–2129} }
 @article{manson_carreiro_lapidus_stephens_goddard_del sesto_bendix_ghannadzadeh_franke_singleton_et al._2012, title={Influence of HF2- geometry on magnetic interactions elucidated from polymorphs of the metal-organic framework [Ni(HF2)(pyz)(2)]PF6 (pyz = pyrazine)}, volume={41}, number={24}, journal={Dalton Transactions (Cambridge, England : 2003)}, author={Manson, J. L. and Carreiro, K. E. and Lapidus, S. H. and Stephens, P. W. and Goddard, P. A. and Del Sesto, R. E. and Bendix, J. and Ghannadzadeh, S. and Franke, I. and Singleton, J. and et al.}, year={2012}, pages={7235–7243} }
 @article{manson_baldwin_scott_bendix_del sesto_goddard_kohama_tran_ghannadzadeh_singleton_et al._2012, title={[Ni(HF2)(3-Clpy)(4)]BF4 (py = pyridine): Evidence for spin exchange along strongly distorted F center dot center dot center dot H center dot center dot center dot F- bridges in a one-dimensional polymeric chain}, volume={51}, number={14}, journal={Inorganic Chemistry}, author={Manson, J. L. and Baldwin, A. G. and Scott, B. L. and Bendix, J. and Del Sesto, R. E. and Goddard, P. A. and Kohama, Y. and Tran, H. E. and Ghannadzadeh, S. and Singleton, J. and et al.}, year={2012}, pages={7520–7528} }
 @article{kan_wu_lee_kang_whangbo_2011, title={On the High Magnetic-Ordering Temperature of the 5d Magnetic Oxide Ca3LiOsO6 Crystallizing in a Trigonal Crystal Structure: Density Functional Analysis}, volume={50}, ISSN={["0020-1669"]}, DOI={10.1021/ic200305a}, abstractNote={The 5d magnetic oxide Ca(3)LiOsO(6) has a trigonal arrangement of its LiOsO(6) chains parallel to the c-direction and hence has triangular arrangements of high-spin Os(5+) (d(3)) ions but exhibits no spin frustration and undergoes a long-range antiferromagnetic ordering at a high temperature. The origin of this apparently puzzling observation was examined by evaluating the nearest-neighbor Os-O···O-Os spin exchange interactions of Ca(3)LiOsO(6) on the basis of density functional calculations. Our study shows that, of the two nearest-neighbor interchain spin exchanges, one dominates over the other and that the intrachain spin exchange and the dominating interchain spin exchange are strong and form a three-dimensional antiferromagnetic spin lattice with no spin frustration, which is responsible for the long-range antiferromagnetic ordering of Ca(3)LiOsO(6) at high temperature. In determining the strengths of the Os-O···O-Os exchange interactions of Ca(3)LiOsO(6), the Li(+) and Ca(2+) ions of the O···Li(+)···O and O···Ca(2+)···O linkages are found to play only a minor role.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Kan, Erjun and Wu, Fang and Lee, Changhoon and Kang, Jinhee and Whangbo, Myung-Hwan}, year={2011}, month={May}, pages={4182–4186} }
 @article{musfeldt_liu_li_kang_lee_jena_manson_schlueter_carr_whangbo_2011, title={Pressure-Induced Local Structure Distortions in Cu(pyz)F-2(H2O)(2)}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic2008039}, abstractNote={We employed infrared spectroscopy along with complementary lattice dynamics and spin density calculations to investigate pressure-driven local structure distortions in the copper coordination polymer Cu(pyz)F(2)(H(2)O)(2). Here, pyz is pyrazine. Our study reveals rich and fully reversible local lattice distortions that buckle the pyrazine ring, disrupt the bc-plane O-H···F hydrogen-bonding network, and reinforce magnetic property switching. The resiliency of the soft organic ring is a major factor in the stability of this material. Interestingly, the collective character of the lattice vibrations masks direct information on the Cu-N and Cu-O linkages through the series of pressure-induced Jahn-Teller axis switching transitions, although Cu-F bond softening is clearly identified above 3 GPa. These findings illustrate the importance of combined bulk and local probe techniques for microscopic structure determination in complex materials.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Musfeldt, J. L. and Liu, Z. and Li, S. and Kang, J. and Lee, C. and Jena, P. and Manson, J. L. and Schlueter, J. A. and Carr, G. L. and Whangbo, M. -H.}, year={2011}, month={Jul}, pages={6347–6352} }
 @article{law_reuvekamp_glaum_lee_kang_whangbo_kremer_2011, title={Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4}, volume={84}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.84.014426}, abstractNote={The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO${}_{4}$, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, electron paramagnetic resonance and dielectric capacitance measurements, and density functional evaluations of the intrachain and interchain spin-exchange interactions. We found type-II multiferroicity below the N\'eel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (${J}_{\mathrm{nn}}$) and next-nearest-neighbor (${J}_{\mathrm{nnn}}$) intrachain spin-exchange interactions. Experimental and theoretical results indicate that the ratio ${J}_{\mathrm{nn}}$/${J}_{\mathrm{nnn}}$ is close to 2, putting CuCrO${}_{4}$ in the vicinity of the Majumdar-Ghosh point.}, number={1}, journal={PHYSICAL REVIEW B}, author={Law, J. M. and Reuvekamp, P. and Glaum, R. and Lee, C. and Kang, J. and Whangbo, M. -H. and Kremer, R. K.}, year={2011}, month={Jul} }
 @article{manson_lapidus_stephens_peterson_carreiro_southerland_lancaster_blundell_steele_goddard_et al._2011, title={Structural, Electronic, and Magnetic Properties of Quasi-1D Quantum Magnets [Ni(HF2)(pyz)(2)]X (pyz = pyrazine; X = PF6-, SbF6-) Exhibiting Ni-FHF-Ni and Ni-pyz-Ni Spin Interactions}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic102532h}, abstractNote={[Ni(HF(2))(pyz)(2)]X {pyz = pyrazine; X = PF(6)(-) (1), SbF(6)(-) (2)} were structurally characterized by synchrotron X-ray powder diffraction and found to possess axially compressed NiN(4)F(2) octahedra. At 298 K, 1 is monoclinic (C2/c) with unit cell parameters, a = 9.9481(3), b = 9.9421(3), c = 12.5953(4) Å, and β = 81.610(3)° while 2 is tetragonal (P4/nmm) with a = b = 9.9359(3) and c = 6.4471(2) Å and is isomorphic with the Cu-analogue. Infinite one-dimensional (1D) Ni-FHF-Ni chains propagate along the c-axis which are linked via μ-pyz bridges in the ab-plane to afford three-dimensional polymeric frameworks with PF(6)(-) and SbF(6)(-) counterions occupying the interior sites. A major difference between 1 and 2 is that the Ni-F-H bonds are bent (∼157°) in 1 but are linear in 2. Ligand field calculations (LFT) based on an angular overlap model (AOM), with comparison to the electronic absorption spectra, indicate greater π-donation of the HF(2)(-) ligand in 1 owing to the bent Ni-F-H bonds. Magnetic susceptibility data for 1 and 2 exhibit broad maxima at 7.4 and 15 K, respectively, and λ-like peaks in dχT/dT at 6.2 and 12.2 K that are ascribed to transitions to long-range antiferromagnetic order (T(N)). Muon-spin relaxation and specific heat studies confirm these T(N)'s. A comparative analysis of χ vs T to various 1D Heisenberg/Ising models suggests moderate antiferromagnetic interactions, with the primary interaction strength determined to be 3.05/3.42 K (1) and 5.65/6.37 K (2). However, high critical fields of 19 and 37.4 T obtained from low temperature pulsed-field magnetization data indicate that a single exchange constant (J(1D)) alone is insufficient to explain the data and that residual terms in the spin Hamiltonian, which could include interchain magnetic couplings (J(⊥)), as mediated by Ni-pyz-Ni, and single-ion anisotropy (D), must be considered. While it is difficult to draw absolute conclusions regarding the magnitude (and sign) of J(⊥) and D based solely on powder data, further support offered by related Ni(II)-pyz compounds and our LFT and density-functional theory (DFT) results lead us to a consistent quasi-1D magnetic description for 1 and 2.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Manson, Jamie L. and Lapidus, Saul H. and Stephens, Peter W. and Peterson, Peter K. and Carreiro, Kimberly E. and Southerland, Heather I. and Lancaster, Tom and Blundell, Stephen J. and Steele, Andrew J. and Goddard, Paul A. and et al.}, year={2011}, month={Jul}, pages={5990–6009} }
 @article{tassel_kang_lee_hernandez_qiu_paulus_collet_lake_guidi_whangbo_et al._2010, title={Ferromagnetically Coupled Shastry-Sutherland Quantum Spin Singlets in (CuCl)LaNb2O7}, volume={105}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.105.167205}, abstractNote={A thorough crystal structure determination at very low temperature of (CuCl)LaNb₂O₇, originally proposed as a spin-1/2 square-lattice antiferromagnet, is reported thanks to the use of single-crystal x-ray diffraction and powder neutron diffraction. State-of-the-art calculations (maximum entropy method) reveal that (CuCl)LaNb₂O₇ is orthorhombic with Pbam symmetry. First-principles calculations demonstrate that the dominant magnetic interactions are antiferromagnetic between fourth nearest neighbors with a Cu-Cl-Cl-Cu exchange path, which lead to the formation of spin singlets. The two strongest interactions between the singlets are ferromagnetic, which makes (CuCl)LaNb₂O₇ the first system of ferromagnetically coupled Shastry-Sutherland quantum spin singlets.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Tassel, C. and Kang, J. and Lee, C. and Hernandez, O. and Qiu, Y. and Paulus, W. and Collet, E. and Lake, B. and Guidi, T. and Whangbo, M-H and et al.}, year={2010}, month={Oct} }
 @article{manson_lancaster_blundell_qiu_singleton_sengupta_pratt_kang_lee_whangbo_2010, title={Spin fluctuations and orbital ordering in quasi-one-dimensional alpha-Cu(dca)(2)(pyz) {dca = dicyanamide = N(CN)(2)(-); pyz = pyrazine}, a molecular analogue of KCuF3}, volume={29}, ISSN={["0277-5387"]}, DOI={10.1016/j.poly.2009.06.063}, abstractNote={The magnetic properties of α-Cu(dca)2(pyz) were examined by magnetic susceptibility, magnetization, inelastic neutron scattering (INS), muon-spin relaxation (μSR) measurements and by first-principles density functional theoretical (DFT) calculations and quantum Monte Carlo (QMC) simulations. The χ versus T curve shows a broad maximum at 3.5 K, and the data between 2 and 300 K is well described by an S = 1/2 Heisenberg uniform chain model with g = 2.152(1) and J/kB = −5.4(1) K. μSR measurements, conducted down to 0.02 K and as a function of longitudinal magnetic field, show no oscillations in the muon asymmetry function A(t). This evidence, together with the lack of spin wave formation as gleaned from INS data, suggests that no long-range magnetic order takes place in α-Cu(dca)2(pyz) down to the lowest measured temperatures. Electronic structure calculations further show that the spin exchange is significant only along the Cu–pyz–Cu chains, such that α-Cu(dca)2(pyz) can be described by a Heisenberg antiferromagnetic chain model. Further support for this comes from the M versus B curve, which is strongly concave owing to the reduced spin dimensionality. α-Cu(dca)2(pyz) is a molecular analogue of KCuF3 owing to dx2-y2 orbital ordering where nearest-neighbor magnetic orbital planes of the Cu2+ sites are orthogonal in the planes perpendicular to the Cu–pyz–Cu chains.}, number={1}, journal={POLYHEDRON}, author={Manson, Jamie L. and Lancaster, Tom and Blundell, Stephen J. and Qiu, Yiming and Singleton, John and Sengupta, Pinaki and Pratt, Francis L. and Kang, Jinhee and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2010}, month={Jan}, pages={514–520} }
 @article{kang_lee_kremer_whangbo_2009, title={Consequences of the intrachain dimer-monomer spin frustration and the interchain dimer-monomer spin exchange in the diamond-chain compound azurite Cu-3(CO3)(2)(OH)(2)}, volume={21}, number={39}, journal={Journal of Physics. Condensed Matter}, author={Kang, J. and Lee, C. and Kremer, R. K. and Whangbo, M. H.}, year={2009} }
 @article{lee_kang_lee_whangbo_2009, title={Density Functional Investigation of the Antiferromagnetic Ordering, Spin Orientation, and Ferroelectric Polarization of Rare-Earth Iron Borate TbFe3(BO3)(4)}, volume={21}, ISSN={["1520-5002"]}, DOI={10.1021/cm9006475}, abstractNote={First-principles density functional calculations were carried out to examine the electronic and magnetic properties of rare-earth iron borate TbFe3(BO3)4. The spin exchange interactions between the Fe3+ (d5, S = 5/2) ions and the preferred orientation of the Tb3+ (f8) spins were evaluated, and the ferroelectric polarization of TbFe3(BO3)4 was calculated. In agreement with experiment, our calculations predict that the spin exchange between the Fe3+ spins is ferromagnetic within each //ab sheet of Fe3+ ions but antiferromagnetic between adjacent //ab sheets of Fe3+ ions, whereas the spin exchange between the Fe3+ and Tb3+ ions within each //ab sheet of Fe3+ and Tb3+ ions is antiferromagnetic. The Tb3+ (f8) ions is found to possess an electron configuration responsible for uniaxial magnetism, hence orienting the Tb3+ spins along the c-direction and leading to the highly anisotropic magnetic susceptibility. The ferroelectric polarization of TbFe3(BO3)4 is largely due to the absence of inversion symmetry of th...}, number={12}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Kang, Jinhee and Lee, Kee Hag and Whangbo, Myung-Hwan}, year={2009}, month={Jun}, pages={2534–2539} }
 @article{musfeldt_vergara_brinzari_lee_tung_kang_wang_schlueter_manson_whangbo_2009, title={Magnetoelastic Coupling through the Antiferromagnet-to-Ferromagnet Transition of Quasi-Two-Dimensional [Cu(HF2)(pyz)(2)]BF4 Using Infrared Spectroscopy}, volume={103}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.103.157401}, abstractNote={We investigated magnetoelastic coupling through the field-driven transition to the fully polarized magnetic state in quasi-two-dimensional [Cu(HF2)(pyz)2]BF4 by magnetoinfrared spectroscopy. This transition modifies out-of-plane ring distortion and bending vibrational modes of the pyrazine ligand. The extent of these distortions increases with the field, systematically tracking the low-temperature magnetization. These distortions weaken the antiferromagnetic spin exchange, a finding that provides important insight into magnetic transitions in other copper halides.}, number={15}, journal={PHYSICAL REVIEW LETTERS}, author={Musfeldt, J. L. and Vergara, L. I. and Brinzari, T. V. and Lee, C. and Tung, L. C. and Kang, J. and Wang, Y. J. and Schlueter, J. A. and Manson, J. L. and Whangbo, M. -H.}, year={2009}, month={Oct} }
 @article{lee_kang_lee_whangbo_2009, title={Symmetry-Dependent Strong Reduction of the Spin Exchange Interactions in Cs2CuCl4 by the 6p Orbitals of Cs+ Ions}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic802412x}, abstractNote={Despite a three-dimensional arrangement of its CuCl(4)(2-) ions, the magnetic properties of Cs(2)CuCl(4) are explained by a two-dimensional frustrated triangular antiferromagnetic spin-lattice. The origin of this low-dimensional magnetism was explored by evaluating the spin exchange interactions of A(2)CuCl(4) (A = Cs, Rb, K, Na) on the basis of first principles density functional calculations. The calculated spin exchange parameters agree with experiment only when the Cs(+) ions located between the CuCl(4)(2-) ions are not neglected. The antiferromagnetic spin exchange interaction between adjacent CuCl(4)(2-) ions is strongly reduced by the 6p orbitals of the intervening Cs(+) ions when the arrangement of the CuCl(4)(2-) and Cs(+) ions has either mirror-plane or inversion symmetry. The observed magnetism of Cs(2)CuCl(4) arises from this symmetry-dependent participation of the 6p orbitals of the Cs(+) ions in the spin exchange interactions between CuCl(4)(2-) ions.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Lee, Changhoon and Kang, Jinhee and Lee, Kee Hag and Whangbo, Myung-Hwan}, year={2009}, month={May}, pages={4165–4170} }
 @article{suh_park_kang_hwang_jung_kim_lee_whangbo_2008, title={Investigation of the scanning tunneling microscopy image, the stacking pattern and the bias-voltage dependent structural imstability of 2,2'-bipyridine molecules adsorbed on Au(111) in terms of electronic structure calculations}, volume={29}, number={2}, journal={Bulletin of the Korean Chemical Society}, author={Suh, Y. and Park, S. S. and Kang, J. and Hwang, Y. G. and Jung, D. and Kim, D. H. and Lee, K. H. and Whangbo, M. H.}, year={2008}, pages={438–444} }