We propose experimental verification and theoretical explanation of magnetic anomalies in the complex Fe-contained double perovskite multiferroics like PbFe1/2Nb1/2O3. The theoretical part is based on our model of coexistence of long-range magnetic order and spin glass in the above substances. In our model, the exchange interaction is anisotropic, coupling antiferromagnetically z spin components of Fe3+ ions. At the same time, the xy components are coupled by much weaker exchange interaction of ferromagnetic sign. In the system with spatial disorder (half of corresponding lattice cites are occupied by spinless Nb5+ ions) such frustrating interaction results in the fact that antiferromagnetic order is formed by z projection of the spins, while their xy components contribute to spin glass behaviour. Our theoretical findings are supported by the experimental evidence of coexistence of antiferromagnetic and spin glass phases in chemically disordered Fe-contained double perovskite multiferroics.
@article{arxiv.1512.08725,
title = {Transversal spin freezing and re-entrant spin glass phase in chemically disordered Fe-contained double perovskite multiferroics},
author = {V. A. Stephanovich and V. V. Laguta},
journal= {arXiv preprint arXiv:1512.08725},
year = {2016}
}