Magnetic structure of ß-cobalt hydroxide and the effect of spin-orientation

DIEGO HUNT; VALERIA FERRARI; JOSE ALBERTO RODRIGUEZ VELAMAZAN; DAMIAN A SCHERLIS; GASTON GARBARINO; MATIAS JOBBAGY

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016 vol. 18 p. 30407 - 30414

1463-9076

Synchrotron X-ray and neutron diffraction experiments at various temperatures, down to 3 K, along withab initiocalculations, are carried out to elucidate the magnetic order of layeredb-cobalt-hydroxide. Thiscombination of techniques allows for the unambiguous assignment of the magnetic structure of thismaterial. Our results confirm that below the Ne ́el temperature high-spin cobaltcenters are ferromagneticallycoupled within a layer, and antiferromagnetically coupled across layers (magnetic propagation vectork=(0,0,12)), in agreement with the indirect interpretation based on magnetic susceptibility measurements.A paramagnetic/antiferromagnetic transition is observed at around 15 K. Moreover, the thermal expansionbehavior along thec-lattice direction, perpendicular to the layers, shows an inflection slightly above thistemperature, at around 30 K. The neutron diffraction patterns and the non-collinear DFT+Ucalculationsindicate that the magnetization forms an angle of about 351with the cobalt planes. In particular, for anisolated ferromagnetic layer, the electronic structure calculations reveal sharp cusps on the potentialenergy surface when the spins point parallel or perpendicular to the planes, suggesting that theferromagnetic superexchange mechanism is strongly sensitive to the orientation of the magnetic moment