Regular Article

Magnetic frustration in lyonsite-type vanadates in FeVO₄–Co₃V₂O₈ system

¹ Institute of Physics, Faculty of Mechanical Engineering and Mechatronic, West Pomeranian University of Technology, Szczecin, Al. Piastow 48, 70-311 Szczecin, Poland
² Department of Inorganic and Analytical Chemistry, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Szczecin, Al. Piastow 42, 71-065 Szczecin, Poland
³ Department of Electrical Engineering, Ajman University of Science and Technology, PO Box 346, Ajman, UAE

^* e-mail: gzolnierkiewicz@zut.edu.pl

Received: 20 July 2018
Received in final form: 25 October 2018
Accepted: 19 November 2018
Published online: 19 December 2018

Abstract

Six phases crystallizing in the lyonsite-type structure were synthesized by solid-state reaction between nFeVO₄ and (1–n)Co₃V₂O₈, where n = 0.73, 0.7143, 0.6667, 0.5843, 0.57, and 0.56. DC magnetic susceptibility in high-temperature range (T  > 100 K) was found to follow the Curie–Weiss law with negative and large value of the Curie–Weiss temperature. The effective magnetic moments were slightly bigger than for high-spin Co²⁺ and Fe³⁺ ions. Spin-glass-like features observed in magnetic FC/ZFC susceptibilities at low temperatures (T  < 15 K) could be the result of a huge magnetocrystalline anisotropy of randomly oriented crystallites or magnetic nanoclusters in the powder samples, or they could be due to magnetic frustration arising from competition of ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. The presence of FM component with a large coercive field and strong magnetic remanence in samples with large Co content was evidenced at low temperature. Weak and very broad electron paramagnetic resonance (EPR) spectra were analyzed by decomposition on Lorentzian components and were attributed to magnetic spin clusters or metallic precipitates not involved in bulk magnetism registered in magnetization measurements. In addition, for n = 0.7143, 0.6667 samples, the much narrower line was due to the V⁴⁺ magnetic defects connected with oxygen vacancies.