Akira Ohkubo

Optical and magnetic properties of CuMnO2 epitaxial thin films with a delafossite-derivative structure

A distorted delafossite CuMnO2, called crednerite, was formed into epitaxial thin films on MgAl2O4 (111) substrates by pulsed laser deposition method. X-ray diffraction revealed that the films had high crystalline quality with epitaxial relationship of CuMnO2 (001)//MgAl2O4 (111) and CuMnO2 [100]//MgAl2O4 ⟨11-2⟩. The ultraviolet-visible optical response revealed a distinct absorption peak at 4.5 eV presumably with excitonic nature and broad peaks at 3.0 and 3.7 eV assignable to O 2p–Mn 3d charge transfer excitation. Small magnetic hysteresis with remanent magnetization of 0.04μB/Mn was observed below 20 K, representing canted antiferromagnetic spin ordering.

High-Throughput Screening of Ultraviolet–Visible Magnetooptical Properties of Spinel Ferrite (Zn,Co)Fe2O4 Solid Solution Epitaxial Film by a Composition-Spread Approach

Spinel ferrite Zn1-xCoxFe2O4 (0≤x≤1) (111) composition-spread thin film was epitaxially grown on an MgAl2O4(111) substrate by combinatorial pulsed laser deposition. Sequential deposition of the two end-compounds with monolayer-period led to the formation of solid solution with addressable composition. Point-by-point ultraviolet–visible magnetic circular dichroism and Faraday rotation angle spectra showed a significant variation with x, and the latter spectra combined with absorption spectra led to the rapid evaluation of magnetooptical performance factor as functions of x and photon energy. A significant enhancement of ultraviolet magnetooptical effect was observed by substituting a small amount of Zn (≤30 at. %) for Co in CoFe2O4.