Iron vacancy effect on the magnetization of YbFe₂O₄

Abstract

We report the effect of iron vacancies on the magnetic property of spin and charge ordered system YbFe 2 O 4 single crystals. The excess amount of iron compensates for the evaporation of iron during crystal growth. We concluded that samples grown with the standard method contain iron vacancies of more than 10%. It is considered that increasing the iron in the starting material recovers the iron stoichiometry, and the proper magnetic property appears. With recovery of the chemical stoichiometry, the magnetic hysteresis loop changes from a double loop to a single loop, which indicates the development of spin coherence and the appearance of a large ferrimagnetic domain. The anomaly found in the thermomagnetization curve at approximately 150 K, the so-called T LT transition, disappears with better stoichiometry. This fact indicates that T LT is not a kind of phase transition but an effect of iron vacancy. Our discovery demonstrates that most of the crystals used in RFe 2 O 4 research might contain many iron vacancies. The confused discussions on this material about the spin order model, the charge order model, and so on might reconsider such chemical stoichiometry, including iron vacancies.

Possible charge order structure of stoichiometric YbFe2O4

“…The variation of the oxygen vacancies affects the population ratio of Fe 2+ and Fe 3+ in triangular lattice. Recently we found that the single crystal grown with a standard protocol contains significant amount of iron vacancies [15]. We also found that the crystal having less iron vacancy i.e., the stoichiometric sample, shows longer spin coherence and pure ferri-magnetism.…”

Magnetic and electrical transport properties of YbFe2O4

“…In fact, our magnetization data are very similar and consistent with the data reported by other researchers. 11,[28][29][30] While LFO goes through a magnetostructural transition at T LT ∼ 175 K, 8,17 YbFO does not show such transition. The broad peak at 190 K, however, indicates a change in the spin structures as a result of interaction between spins on different Fe sub-lattices and spin fluctuations.…”

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“…The single and double hysteresis loops are observed in stoichiometric and off-stoichiometric samples, respectively. 30 The peak in zero field cooling (ZFC) curve also indicates high stoichiometry. 30 As for Figure 3, the relatively high stoichiometry of the film on SiC substrate is indicated by the peak in ZFC curve and near single hysteresis loop in M-H curve.…”

“…30 The peak in zero field cooling (ZFC) curve also indicates high stoichiometry. 30 As for Figure 3, the relatively high stoichiometry of the film on SiC substrate is indicated by the peak in ZFC curve and near single hysteresis loop in M-H curve. 23,30 The Neel temperature (T N ) is a little lower than that of the bulk, which likely to arise from lower crystallization or longer c-axis and shorter a-and b-axes by stress from the substrate.…”