Ferromagnetism in Co7(TeO3)4Br6: A byproduct of complex antiferromagnetic order and single-ion anisotropy

Prester, Mladen and Živković, Ivica and Zaharko, O. and Pajić, Damir and Tregenna-Piggott, P. and Berger, Helmut (2009) Ferromagnetism in Co7(TeO3)4Br6: A byproduct of complex antiferromagnetic order and single-ion anisotropy. Physical Review B, 79 (14). pp. 144433-1. ISSN 1098-0121

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Pronounced anisotropy of magnetic properties and complex magnetic order of a new oxi-halide compound Co7(TeO3)4Br6 has been investigated by powder and single-crystal neutron-diffraction, magnetization, and ac susceptibility techniques. Anisotropy of susceptibility extends far into the paramagnetic temperature range. A principal source of anisotropy are anisotropic properties of the involved octahedrally coordinated single Co2+ ions, as confirmed by angular-overlap-model calculations presented in this work. Incommensurate antiferromagnetic order sets in at TN=34 K. The propagation vector is strongly temperature dependent reaching k1=(0.9458(6) ,0,0.6026(5)) at 30 K. A transition to a ferrimagnetic structure with k2=0 takes place at TC=27 K. The magnetically ordered phase is characterized by very unusual anisotropy as well: while M-H scans along the b axis reveal spectacularly rectangular but otherwise standard ferromagnetic hysteresis loops, M-H studies along other two principal axes are perfectly reversible, revealing very sharp spin-flop (or spin-flip) transitions, such as in a standard antiferromagnet (or metamagnet). Altogether, the observed magnetic phenomenology is interpreted as an evidence of competing magnetic interactions permeating the system, in particular of the single-ion anisotropy energy and the exchange interactions. Different coordinations of the Co2+ ions involved in the low-symmetry C2/c structure of Co7(TeO3)4Br6 render the exchange-interaction network very complex by itself. Temperature-dependent changes in the magnetic structure, together with an abrupt emergence of a ferromagnetic component, are ascribed to continual spin reorientations described by a multicomponent, but yet unknown, spin Hamiltonian.

Item Type: Article
Keywords: magnetic order, magnetic interactions
Date: April 2009
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2009) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Project code: 035-0352843-2845, 119-1191458-1017
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 17 May 2014 12:17
Last Modified: 17 May 2014 12:19
URI: http://digre.pmf.unizg.hr/id/eprint/1420

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