Transversal spin freezing and re-entrant spin glass phase in chemically disordered Fe-contained double perovskite multiferroics

TL;DR

This paper investigates the coexistence of antiferromagnetic order and spin glass behavior in chemically disordered Fe-containing double perovskite multiferroics, supported by theoretical modeling and experimental evidence.

Contribution

It introduces a model explaining the coexistence of long-range magnetic order and spin glass phases in disordered double perovskites, supported by experimental verification.

Findings

Evidence of coexisting antiferromagnetic and spin glass phases.

Theoretical model explains anisotropic exchange interactions leading to observed phenomena.

Experimental data supports the coexistence of magnetic phases.

Abstract

We propose experimental verification and theoretical explanation of magnetic anomalies in the complex Fe-contained double perovskite multiferroics like PbFe$_{1/2}$Nb$_{1/2}$O$_3$. 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 Fe$^{3+}$ 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 Nb$^{5+}$ 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.