Review of thin films of RFe2O4 (R=Lu, Yb, Tm or In)

The strongly correlated electron system has been attracted much attention in solid state physics due to its abnormal electric, magnetic and optical properties which promises novel application. Rare earth ion ferrite RFe2O4 (R = Y, Dy, Ho, Er, Tm, Yb, Lu, Sc, or In) is the typical example. This material is composed of doubly stacked iron triangular layers (W-layer) separated by single rare-earth triangular layer.1 Equal amounts of Fe2+ and Fe3+ exist on triangular lattices and form charge orders due to the Coulombic interaction between iron ions.2,3 The charge ordered W-layers stack randomly and regularly above and below threedimensional charge ordering temperature, respectively.