Unravelling the elusive antiferromagnetic order in wurtzite and zinc blende CoO polymorph nanoparticles

Authors:
A. G. Roca, I. V. Golosovsky, E. Winkler, A. López-Ortega, M. Estrader, R. D. Zysler, M. D. Baró, J. Nogués
The year of the publication:
2018
Journal:
Small, (Wiley-VCH Verlag GmbH & Co) N 15 vol. 14 1703963-1703975
Abstract:

Although cubic rock salt-CoO has been extensively studied, the magnetic properties of the main nanoscale CoO polymorphs (hexagonal wurtzite and cubic zinc blende structures) are rather poorly understood. Here we present a detailed magnetic and neutron diffraction studies on zinc blende and wurtzite CoO nanoparticles. The zinc blende-CoO phase is antiferromagnetic with a 3rd type structure in a fcc lattice and a Néel temperature of TN (zinc-blende) ~ 225 K. Wurtzite-CoO also presents an antiferromagnetic order, TN (wurtzite) ~ 109 K, although much more complex, with a 2nd type order along the c-axis but an incommensurate order along the y-axis. Importantly, the overall magnetic properties are overwhelmed by the uncompensated spins, which confer the system a ferromagnetic–like behavior even at room temperature.

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