Absence of polar order in LuFe2O4

TL;DR

This study demonstrates that LuFe2O4 does not exhibit intrinsic ferroelectricity or polar order, and its previously reported colossal dielectric constants are surface-related artifacts, challenging its classification as a multiferroic.

Contribution

The paper provides experimental evidence that LuFe2O4 lacks intrinsic ferroelectricity, clarifying its dielectric properties and refuting its status as a multiferroic material.

Findings

Colossal dielectric constants are surface-related, not intrinsic.

Intrinsic dielectric constant is approximately 20.

No evidence of ferroelectric order in LuFe2O4.

Abstract

LuFe2O4 often is considered as a prototypical multiferroic with polar order arising from the electronic degrees of freedom only ("electronic ferroelectricity"). In the present work, we check the intrinsic nature of the dielectric response of this material by performing dielectric measurements of polycrystalline samples with different types of contact materials and with different grain sizes. In addition, frequency-dependent measurements of the electric-field dependent polarization are provided. The obtained results unequivocally prove that the reported colossal dielectric constants in LuFe2O4, which were interpreted in terms of electronic ferroelectricity, are of non-intrinsic surface-related origin. The intrinsic dielectric properties of this material show no indications of any ferroelectric order and, thus, LuFe2O4 is not multiferroic. Its intrinsic dielectric constant is close to 20 and its dielectric loss is dominated by charge transport via variable range hopping.