Magnetic properties of highly ordered single crystals with layered YBaCuFeO₅ structure

¹ Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Spain
² Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France

^* Corresponding author: garcia.munoz@icmab.es

Published online: 9 October 2023

Abstract

In the layered perovskites YBaCuFeO₅ (YBCFO) magnetic frustration stabilizes incommensurate spiral order up to unexpectedly high temperatures (TS). The level of frustration and hence TS depend directly on the fraction (n_d) of B-site (Cu/Fe) chemical disorder in the samples. We report a neutron investigation on the magnetic transitions in two YBaCuFeO₅ single crystals (one pure and the second slightly doped with Mn), grown by floating-zone methods, that present very low Fe/Cu cation disorder (n_d→0). The low density of antiferromagnetic Fe₂O₉ bipyramid units in these crystals precludes the stabilization of a frustrated topological network, which is at the origin of the non-collinear (helicoidal) magnetic order. Instead, the ground state is substituted by two competing commensurate collinear magnetic phases, the majority one (k1) attributed to the perfectly ordered YBCFO perovskite (n_d=0). A second type of collinear magnetic domains (k3) develop for samples with disorder below a critical threshold (0<n_d< n₀). Only in YBCFO samples with Cu/Fe disorder above the critical threshold a long-range helicoidal or spiral magnetic state can be formed.