Frustration-driven non-collinear magnetism and AC-conduction mechanism in YBaCuFeO5 double perovskite

Abstract

A numerical determination of exchange interactions governing frustration-driven non-collinear magnetism in YBaCuFeO5 is presented. Temperature-dependent neutron diffraction provides the experimental propagation vector, which is mapped onto a Heisenberg model, and the exchange ratios are uniquely extracted using a null-space (singular value decomposition) approach. The numerically obtained exchange ratios reveal the frustrated balance of competing interactions, stabilizing the incommensurate helical ordering in the presence of tetragonal distortion and B-site disorder. X-ray photoelectron spectroscopy and Mössbauer spectroscopy confirm the stability of B-site oxidation states and the local Fe environment. Dielectric and impedance measurements reveal Maxwell–Wagner polarization and non-Debye relaxation dominated by grain boundaries, while conductivity follows a thermally activated polaronic mechanism consistent with a correlated barrier hopping model. The explicit spiral magnetic ordering, with numerically determined exchange-integral ratios and in-depth conduction mechanisms, provides a new dimension to YBaCuFeO5, enhancing its applicability in spintronics and multiferroics.