Pressure‐Induced Sequential Orbital Reorientation in a Magnetic Framework Material

Halder, Gregory J.; Chapman, Karena W.; Schlueter, John A.; Manson, Jamie L.

doi:10.1002/ange.201003380

Cited by 15 publications

(18 citation statements)

References 13 publications

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“…Hence the system becomes Q1D due to the dominance of J 3 . This pressure-induced switching of orbital orientation and system dimensionality is analogous to the transitions reported for the "monolayer" material [CuF 2 (H 2 O) 2 pyz] [42,43] and occurs despite the differences in Cu 2+ coordination. In neither case does the reorientation affect the covalently bonded part of the structure, although it modifies slightly the non-covalent interactions.…”

supporting

confidence: 70%

Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet

et al. 2018

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We report an extraordinary pressure dependence of the magnetic interactions in the metal-organic system [CuF_{2}(H_{2}O)_{2}]_{2}pyrazine. At zero pressure, this material realizes a quasi-two-dimensional spin-1/2 square-lattice Heisenberg antiferromagnet. By high-pressure, high-field susceptibility measurements we show that the dominant exchange parameter is reduced continuously by a factor of 2 on compression. Above 18 kbar, a phase transition occurs, inducing an orbital re-ordering that switches the dimensionality, transforming the quasi-two-dimensional lattice into weakly coupled chains. We explain the microscopic mechanisms for both phenomena by combining detailed x-ray and neutron diffraction studies with quantitative modeling using spin-polarized density functional theory.

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confidence: 70%

Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet

et al. 2018

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“…A study of the Cu(II)-based coordination network compound CuF 2 (H 2 O) 2 (pz) has already shown that hydrostatic pressure can drastically change the magnetic properties of this class of materials. 31 In particular, since some bonds and bridges are softer and others more rigid, pressure can induce non-isotropic deformations, including both axial and angular distortions. Similarly, in the Cu(pz) 2 (ClO 4 ) 2 case, the interlayer interactions and the perchlorate gegenanions are expected to be more sensitive to distortions than the pyrazine bridges.…”

Section: B Nmr Measurementsmentioning

confidence: 99%

Pressure and magnetic field effects on a quasi-two-dimensional spin-12Heisenberg antiferromagnet

et al. 2016

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Cu(pz) 2 (ClO 4 ) 2 (with pz denoting pyrazine, C 4 H 4 N 2 ) is among the best realizations of a two-dimensional spin-1 /2 square-lattice antiferromagnet. Below T N = 4.21 K, its weak interlayer couplings induce a 3D magnetic order, strongly influenced by external magnetic fields and/or hydrostatic pressure. Previous work, focusing on the [H, T ] phase diagram, identified a spin-flop transition, resulting in a field-tunable bicritical point. However, the influence of external pressure has not been investigated yet. Here we explore the extended [p, H, T ] phase diagram of Cu(pz) 2 (ClO 4 ) 2 under pressures up to 12 kbar and magnetic fields up to 7.1 T, via magnetometry and 35 Cl nuclear magnetic resonance (NMR) measurements. The application of magnetic fields enhances T X Y , the crossover temperature from the Heisenberg to the X Y model, thus pointing to an enhancement of the effective anisotropy. The applied pressure has an opposite effect [dT N /dp = −0.050(8) K/kbar], as it modifies marginally the interlayer couplings, but likely changes more significantly the orbital reorientation and the square-lattice deformation. This results in a remodeling of the effective Hamiltonian, whereby the field and pressure effects compensate each other. Finally, by comparing the experimental data with numerical simulations we estimate T BKT , the temperature of the Berezinskii-Kosterlitz-Thouless topological transition and argue why it is inaccessible in our case.

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“…For example, absorption bands 6 ]Cl 2 are blueshifted at high pressure as the result of an increase in ligand-field strength, which occurs as ligand-metal distances shorten. [18] Jahn-Teller distortions can be suppressed by using pressure: [19] the direction of the Jahn-Teller axes are altered [13,20] and Jahn-Teller elongations converted into compressions. [21] The flexibility of the coordination geometry of copper has led to a number of studies of piezochromism in complexes of this metal.…”

Section: Introductionmentioning

confidence: 99%

Piezochromism in Nickel Salicylaldoximato Complexes: Tuning Crystal‐Field Splitting with High Pressure

Byrne

Richardson

Chang

et al. 2012

Chemistry A European J

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The crystal structures of bis(3-fluoro-salicylaldoximato)nickel(II) and bis(3-methoxy-salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6 GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni⋅⋅⋅Ni distance decreases from 3.19 Å at ambient pressure to 2.82 Å at 5.4 GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Ni-ligand distances also shorten, on average by 0.017 and 0.011 Å for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620 nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x(2)-y(2)) orbital. Time-dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Ni-ligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV-visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5 GPa.

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Pressure‐Induced Sequential Orbital Reorientation in a Magnetic Framework Material

Cited by 15 publications

References 13 publications

Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet

Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet

Pressure and magnetic field effects on a quasi-two-dimensional spin-12Heisenberg antiferromagnet

Piezochromism in Nickel Salicylaldoximato Complexes: Tuning Crystal‐Field Splitting with High Pressure

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