02191nas a2200217 4500008004100000022001400041245012900055210007000184260000800254300001400262490000700276520142900283100001601712700001901728700001501747700001901762700001801781700002101799700002101820856013201841 2024 eng d a0020-166900aIntertwining of localized (d) and delocalized (π) spins in magnetically frustrated two-dimensional metal-organic frameworks0 aIntertwining of localized d and delocalized π spins in magnetica cFEB a3675-36810 v633 a

Two-dimensional metal-organic frameworks (2D MOFs) are emerging as a new class of multifunctional materials for diversified applications, although magnetic properties have not been widely explored. The metal ions and organic ligands in some of the 2D MOFs are arranged in the well-known Kagome lattice, leading to geometric spin frustration. Hence, such systems could be the potential candidates to exhibit an exotic quantum spin liquid (QSL) state, as was observed in Cu-3(HHTP)(2) (HHTP = hexahydroxytriphenylene), with no magnetic transition down to 38 mK. Hereto, we have investigated the spin intertwining in a bimetallic 2D MOF system, M-3(HHTP)(2) (M = Cu/Zn)(,) arising from the localized (d-electron) and delocalized (pi-electron) S = 1/2 spins from the Cu(II) ions and the HHTP radicals, respectively. The origin of the spin frustration (down to 5K) was critically examined by varying the metal composition in bimetallic systems, CuxZn3-x(HHTP)(2) (x = 1, 1.5, 2), containing both S = 1/2 and S = 0 spins. Additionally, to gain a deeper understanding, we studied the spin interaction in the pristine Zn-3(HHTP)(2) system containing only S = 0 Zn(II) ions. In view of the quantitative estimate of the localized and delocalized spins, the d-pi spin correlation appears essential in understanding the unusual magnetic and/or other physical properties of such hybrid organic-inorganic 2D crystalline solids

1 aUgale, Ajay1 aNinawe, Pranay1 aJain, Anil1 aSangole, Mayur1 aMandal, Rimpa1 aSingh, Kirandeep1 aBallav, Nirmalya uhttp://library.ncl.res.in/content/intertwining-localized-d-and-delocalized-%CF%80-spins-magnetically-frustrated-two-dimensional02271nas a2200289 4500008004100000022001400041245009400055210006900149260000900218490000700227520134800234653003101582653002001613653002701633653001601660653002101676100001901697700001501716700001901731700001501750700001601765700002101781700002101802700002101823700002101844856011601865 2024 eng d a0947-653900aRobust spin liquidity in 2D metal-organic framework Cu3 (HHTP)2 with S=1/2 kagome lattice0 aRobust spin liquidity in 2D metalorganic framework Cu3 HHTP2 wit cJAN 0 v303 a

On one hand electron or hole doping of quantum spin liquid (QSL) may unlock high-temperature superconductivity and on the other hand it can disrupt the spin liquidity, giving rise to a magnetically ordered ground state. Recently, a 2D MOF, Cu-3(HHTP)(2) (HHTP - 2,3,6,7,10,11-hexahydroxytriphenylene), containing Cu(II) S = 1/2 frustrated spins in the Kagome lattice is emerging as a promising QSL candidate. Herein, we present an elegant in situ redox-chemistry strategy of anchoring Cu-3(HHTP)(2) crystallites onto diamagnetic reduced graphene oxide (rGO) sheets, resulting in the formation of electron-doped Cu-3(HHTP)(2)-rGO composite which exhibited a characteristic semiconducting behavior (5 K to 300 K) with high electrical conductivity of 70 S . m(-1) and a carrier density of similar to 1.1 x 10(18) cm(-3) at 300 K. Remarkably, no magnetic transition in the Cu-3(HHTP)(2)-rGO composite was observed down to 1.5 K endorsing the robust spin liquidity of the 2D MOF Cu-3(HHTP)(2). Specific heat capacity measurements led to the estimation of the residual entropy values of 28 % and 34 % of the theoretically expected value for the pristine Cu-3(HHTP)(2) and Cu-3(HHTP)(2)-rGO composite, establishing the presence of strong quantum fluctuations down to 1.5 K (two times smaller than the value of the exchange interaction J).

10a2D Metal-organic Framework10aElectron doping10aReduced graphene oxide10aSpin Liquid10aSpin-frustration1 aNinawe, Pranay1 aJain, Anil1 aSangole, Mayur1 aAnas, Mohd1 aUgale, Ajay1 aMalik, Vivek, K.1 aYusuf, Seikh, M.1 aSingh, Kirandeep1 aBallav, Nirmalya uhttp://library.ncl.res.in/content/robust-spin-liquidity-2d-metal-organic-framework-cu3-hhtp2-s12-kagome-lattice04906nas a2200229 4500008004100000245007800041210007000119260000800189490000600197520417400203100001804377700001904395700002204414700001704436700001704453700001704470700001604487700002104503700002204524700002104546856010904567 2024 eng d00aUnconventional hole doping of S = ½ kagome antiferromagnet CoCu3(OH)6Cl20 aUnconventional hole doping of S ½ kagome antiferromagnet CoCu3OH cSEP0 v33 a

Geometrically perfect S = ½ kagome lattices with frustrated magnetism are typically electrical insulators. Electron or hole doping is predicted to induce an exotic conducting state including superconductivity. Herein, an unconventional strategy of doping an S = ½ kagome lattice CoCu3(OH)6Cl2 is adopted – a structural analogue of a well-known quantum spin liquid (QSL) candidate herbertsmithite (ZnCu3(OH)6Cl2) – by integrating it with reduced graphene oxide (rGO) via in situ redox chemistry. Such an integration drastically enhances the electrical conductivity, resulting in the transformation of an insulator to a semiconductor, corroborating the respective density of states obtained from the density functional theory calculations. Estimation of the magnetic moments, data on the Hall-effect measurements, Bader charge analysis, and photoemission signals, altogether provide a bold signature of remote hole doping in CoCu3(OH)6Cl2 by rGO. The remote doping provides an alternative to the site doping approach to impart exotic electronic properties in spin liquid candidates, specifically, the generation of topological states like Dirac metal is envisioned.

1 aMandal, Rimpa1 aNinawe, Pranay1 aAnanthram, K., S.1 aMhase, Akash1 aGupta, Kriti1 aSaha, Sauvik1 aUgale, Ajay1 aSingh, Kirandeep1 aTarafder, Kartick1 aBallav, Nirmalya uhttp://library.ncl.res.in/content/unconventional-hole-doping-s-%C2%BD-kagome-antiferromagnet-cocu3oh6cl2