Nanometer-Sized Domain Structures in LuFeMO₄ (M = Cu, Co) Revealed by Energy-Filtered Transmission Electron Microscopy

Abstract

Diluted effect on the charge ordered (CO) structure in dielectric materials LuFeMO₄ (M = Cu, Co) were investigated by an energy-filtered transmission electron microscopy (TEM), in combination with a conventional TEM. It is revealed that partial substitution of Cu^{2 +} and Co^{2 +} for Fe^{2 +}in LuFe₂O₄ destabilized the CO structure. In LuFeCuO₄, there exist characteristic zigzag-shaped diffuse streaks and diffuse spots at the h/3-δ h/3-δ 0-type positions (h: integer, δ = 0.06) in reciprocal space, which originate from static cationic ordering of Fe^{3 +} and Cu^{2 +} ions in the triangular lattice. Moreover, real-space images by the energy-filtered TEM revealed that nanometer-sized domain structures with the 5∼10 nm size are formed. In contrast, honeycomb-shaped diffuse streaks were found in LuFeCoO₄, in which no domain structures are observed in real-space images.

Keywords:

• nanometer-sized domains
• electron diffraction
• dielectric material
• energy-filtered TEM

Acknowledgments

This work was partially supported by a Grant-in-Aid for Scientific Research on Priority Areas “Novel States of Matter Induced by Frustration” (No.19052002) and KIBAN (B) (No.20340078) from the Ministry of Education, Culture, Sports, Science, and Technology in Japan. One of the authors (SM) was supported financially by the Murata Scientific Research foundation.