On the Magnetic Behavior of Polycrystalline Single-Phase YBaCo4O7+δ Obtained by Soft Chemical Synthesis

Abstract

Polycrystalline single-phase YBaCo4O7+δ samples were synthesized by a wet chemistry method based on the so-called citrates route. The structural, morphological, and magnetic properties of the so-obtained samples were carefully studied by standard experimental techniques. The X-ray powder diffraction (XRD) patterns showed reflections of a pure hexagonal structure (space group P63mc) with lattice parameters being very close to those reported in the literature. No evidence of affectation by any secondary phase such as 112 (YBaCo2O5.5) was provided by XRD analysis. This finding was further corroborated by sensible SQUID magnetic measurements which showed signals stemming merely from the desired 114 phase (YBaCo4O7+δ ). A bifurcation in the zero field-cooled (ZFC) and FC magnetization curves below ∼80 K was observed. The M ZFC(T) curve displays a sharp peak at ∼70 K and continues to be different down to the lowest temperature. In turn, the M FC(T) curve shows a sharp rise at ∼80 K and peaks at ∼50 K. The conspicuous increase in the magnetization observed at ∼80 K seems to be correlated with a transition into a long-range ordered antiferromagnetic state. This magnetic behavior is consistent with that observed in YBaCo4O7+δ single crystals. In turn, isothermal magnetization recorded at 70 K showed field-induced effects manifested itself in the appearance of a ferromagnetic component which could be originated by spin canting of the underlying antiferromagnetic state. The possible spin-glass behavior of the studied samples is ruled out through measurements of the real part of the AC susceptibility as a function of the frequency (8–473 Hz) on YBaCo4O7+δ single-crystals. Beyond this relevant result, the collected data demonstrate that the tested chemical route emerges as a suitable alternative to synthesize complex single-phase oxides such as the YBaCo4O7+δ cobaltate.