Interdimeric Couplings and Spin Entanglement in Copper Acetate

SANTANA, VINICIUS T.; SARTORIS, ROSANA P.; NASCIMENTO, OTACIRO R; LAGUTA, OLEKSII; EDIVÝ, MATUS; NEUGEBAUER, PETR; CALVO, RAFAEL

Cardiff

Congreso; 54th Annual International Meeting of the Royal of the ESR Spectroscopy Group of the Royal Society of Chemistry.; 2021

Royal Society of Chemistry, UK

Dimeric compounds having molecular units with pairs of spinsS1and S2connected by intradimeric exchange coupling J0(H0=-J0S1.S2), and magneticallyisolated in a crystal lattice, are non-trivial quantum spin systems, havingprimary roles in magnetism. Copper acetate monohydrate, [Cu(CH3COO)2.H2O],here called CAH, has been investigated over the years and provided importantinformation about superexchange couplings and magnetic behaviour. However, wehave not found studies on the interdimeric couplings J?´ in CAH. They introduce spin entanglement and a spin dynamicshaving a prominent role in the behaviour of molecular magnets. We report amultifrequency Electron Paramagnetic Resonance (EPR) study of CAH in a widerange of T in single-crystal andpowder samples explaining spectral features arising from weak interdimericcouplings (|J?/J0| ~ 10-5). When the two absorption peaks ms=-1↔0and ms=+1↔0 in single-crystal spectra cross at the magicangles, they merge and narrow modulated by J?. As a consequence, powderspectra exhibit an additional feature named U-peak [1,2] shown in the spectraof the figure, collecting the absorptions coming from spins oriented within the?magic rings? (locus of magic angles) indicated in red circles (dimeric site A)and blue circles (dimeric site B) in the sphere of the figure. The orientationscontained in the magic rings give rise to an entangled phase, which may betuned with the orientation of an external magnetic field B0. Otherorientations give rise to the standard dimeric spectrum. We propose a model forthe interdimeric coupling effects, based on the crystal structure and thechemical paths for superexchange, analysing and modelling features of theobserved EPR spectra considering these effects with results that contribute toa better description of the role of this coupling in the magnetic phases.