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Neutron Diffraction Studies of the Molecular Compound [Co2(bta)]n (H4bta =1,2,4,5-Benzenetetracarboxylic Acid): In the Quest of Canted Ferromagnetism

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journal contribution
posted on 04.11.2013, 00:00 by Oscar Fabelo, Laura Cañadillas-Delgado, Jorge Pasán, Pau Díaz-Gallifa, Catalina Ruiz-Pérez, Francesc Lloret, Miguel Julve, Inés Puente Orench, Javier Campo, Juan Rodríguez-Carvajal
The exchange mechanism and magnetic structure of the organic–inorganic layered molecule-based magnet [Co2(bta)]n (1) (H4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an antiferromagnetic ordering at a transition temperature of 16 K that is followed by the appearance of a weak ferromagnetism below 11 K. The weak antiferromagnetic interlayer interaction plays an important role in this system in spite of the long interlayer separation. A ferromagnetic ordering is induced by applied magnetic fields greater than 1800 G (metamagnetic behavior), and a slow magnetic relaxation from this ferromagnetic phase to the antiferromagnetic one is observed. The magnetic structure of 1 has been elucidated at low temperatures in zero field by neutron powder diffraction measurements and was found to be of antiferromagnetic nature with the local cobalt­(II) spins (magnetic moments) being aligned ferromagnetically in the ac plane and antiferromagnetically coupled along the crystallographic b axis. No evidence for a long-range spontaneous ferromagnetic component below 11 K was observed in the neutron experiment.

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