@article{caslin_kremer_razavi_schulz_munoz_pertlik_liu_whangbo_law_2014, title={Characterization of the spin-1/2 linear-chain ferromagnet CuAs2O4}, volume={89}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.89.014412}, abstractNote={The magnetic and lattice properties of the $S$=1/2 quantum-spin-chain ferromagnet, CuAs$_2$O$_4$, mineral name trippkeite, were investigated. The crystal structure of CuAs$_2$O$_4$ is characterized by the presence of corrugated CuO$_2$ ribbon chains. Measurements of the magnetic susceptibility, heat capacity, electron paramagnetic resonance and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic transition occurs at $\sim$7.4 K. $\textit{Ab initio}$ DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next- nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of $J_{\rm nn}$/$J_{\rm nnn}$ is near -4, placing CuAs$_2$O$_4$ in close proximity to a quantum critical point in the $J_{\rm nn}$ - $J_{\rm nnn}$ phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu$^{2+}$ spins to lie in an easy plane perpendicular to the $c$-axis. An analysis of the field and temperature dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasi-hydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy.}, number={1}, journal={PHYSICAL REVIEW B}, author={Caslin, K. and Kremer, R. K. and Razavi, F. S. and Schulz, A. and Munoz, A. and Pertlik, F. and Liu, J. and Whangbo, M. -H. and Law, J. M.}, year={2014}, month={Jan} }
 @article{liu_koo_xiang_kremer_whangbo_2014, title={Most spin-1/2 transition-metal ions do have single ion anisotropy}, volume={141}, number={12}, journal={Journal of Chemical Physics}, author={Liu, J. and Koo, H. J. and Xiang, H. J. and Kremer, R. K. and Whangbo, M. H.}, year={2014} }
 @article{brinzari_chen_sun_liu_tung_wang_schlueter_singleton_manson_whangbo_et al._2013, title={Quantum Critical Transition Amplifies Magnetoelastic Coupling in Mn[N(CN)(2)](2)}, volume={110}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.110.237202}, abstractNote={We report the discovery of a magnetic quantum critical transition in Mn[N(CN)(2)](2) that drives the system from a canted antiferromagnetic state to the fully polarized state with amplified magnetoelastic coupling as an intrinsic part of the process. The local lattice distortions, revealed through systematic phonon frequency shifts, suggest a combined MnN(6) octahedra distortion+counterrotation mechanism that reduces antiferromagnetic interactions and acts to accommodate the field-induced state. These findings deepen our understanding of magnetoelastic coupling near a magnetic quantum critical point and away from the static limit.}, number={23}, journal={PHYSICAL REVIEW LETTERS}, author={Brinzari, T. V. and Chen, P. and Sun, Q. -C. and Liu, J. and Tung, L. -C. and Wang, Y. and Schlueter, J. A. and Singleton, J. and Manson, J. L. and Whangbo, M. -H. and et al.}, year={2013}, month={Jun} }
 @article{lee_liu_whangbo_koo_kremer_simon_2012, title={Investigation of the spin exchange interactions and the magnetic structure of the high-temperature multiferroic CuBr2}, volume={86}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.86.060407}, abstractNote={We report a detailed density functional analysis of the spin exchange interactions and the magnetic structure of the high-temperature multiferroic CuBr${}_{2}$ and compare the results with magnetic susceptibility measurements. CuBr${}_{2}$ shows one-dimensional antiferromagnetism and undergoes long-range antiferromagnetic ordering at $\ensuremath{\sim}$74 K. Due to the competition between the nearest- and next-nearest-neighbor spin exchanges, each Cu${}^{2+}$ chain has a cycloidal spin-spiral structure, which is described approximately by a quadrupling of the nuclear cell with spin moment rotation of $\ensuremath{\sim}$${85}^{\ensuremath{\circ}}$ in the plane of the CuBr${}_{2}$ ribbon plane.}, number={6}, journal={PHYSICAL REVIEW B}, author={Lee, C. and Liu, Jia and Whangbo, M. -H. and Koo, H. -J. and Kremer, R. K. and Simon, A.}, year={2012}, month={Aug} }
 @article{ben yahia_shikano_koike_tatsumi_kobayashi_kawaji_avdeev_miiller_ling_liu_et al._2012, title={Synthesis and characterization of the crystal structure and magnetic properties of the new fluorophosphate LiNaCo[PO4]F}, volume={51}, DOI={10.1021/ic300374w}, abstractNote={The new compound LiNaCo[PO(4)]F was synthesized by a solid state reaction route, and its crystal structure was determined by single-crystal X-ray diffraction measurements. The magnetic properties of LiNaCo[PO(4)]F were characterized by magnetic susceptibility, specific heat, and neutron powder diffraction measurements and also by density functional calculations. LiNaCo[PO(4)]F crystallizes with orthorhombic symmetry, space group Pnma, with a = 10.9334(6), b = 6.2934(11), c = 11.3556(10) Å, and Z = 8. The structure consists of edge-sharing CoO(4)F(2) octahedra forming CoFO(3) chains running along the b axis. These chains are interlinked by PO(4) tetrahedra forming a three-dimensional framework with the tunnels and the cavities filled by the well-ordered sodium and lithium atoms, respectively. The magnetic susceptibility follows the Curie-Weiss behavior above 60 K with θ = -21 K. The specific heat and magnetization measurements show that LiNaCo[PO(4)]F undergoes a three-dimensional magnetic ordering at T(mag) = 10.2(5) K. The neutron powder diffraction measurements at 3 K show that the spins in each CoFO(3) chain along the b-direction are ferromagnetically coupled, while these FM chains are antiferromagnetically coupled along the a-direction but have a noncollinear arrangement along the c-direction. The noncollinear spin arrangement implies the presence of spin conflict along the c-direction. The observed magnetic structures are well explained by the spin exchange constants determined from density functional calculations.}, number={16}, journal={Inorganic Chemistry}, author={Ben Yahia, H. and Shikano, M. and Koike, S. and Tatsumi, K. and Kobayashi, H. and Kawaji, H. and Avdeev, M. and Miiller, W. and Ling, C. D. and Liu, J. and et al.}, year={2012}, pages={8729–8738} }