Isotope effect in quasi-two-dimensional metal-organic antiferromagnets

Abstract

Although the isotope effect in superconducting materials is well-documented, changes in the magnetic properties of antiferromagnets due to isotopic substitution are seldom discussed and remain poorly understood. This is perhaps surprising given the possible link between the quasi-two-dimensional (Q2D) antiferromagnetic and superconducting phases of the layered cuprates. Here we report the experimental observation of shifts in the Néel temperature and critical magnetic fields ($\Delta T_{\mathrm{N}}/T_{\mathrm{N}}\approx 4$; $\Delta B_{\mathrm{c}}/B_{\mathrm{c}}\approx 4$) in a Q2D organic molecular antiferromagnets on substitution of hydrogen for deuterium. These compounds are characterized by strong hydrogen bonds through which the dominant superexchange is mediated. We evaluate how the in-plane and inter-plane exchange energies evolve as the hydrogens on different ligands are substituted, and suggest a possible mechanism for this effect in terms of the relative exchange efficiency of hydrogen and deuterium bonds.

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• Control of the third dimension in copper-based square-lattice antiferromagnets
• Giant pressure dependence and dimensionality switching in a metal-organic quantum antiferromagnet
• Magnetic properties of the S=1/2 quasi square lattice antiferromagnet CuF2(H2O)2(pyz) (pyz=pyrazine) investigated by neutron scattering
• Dimensional reduction by pressure in the magnetic framework material CuF${}_2$(D${}_2$O)${}_2$pyz: from spin-wave to spinon excitations
• Exchange constants in molecule-based magnets derived from density functional methods