Structural and magnetic properties of epitaxial delafossite CuFeO2 thin films grown by pulsed laser deposition

Abstract

Growth of pure phase delafossite CuFeO2 thin films on Al2O3 (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO2 films demonstrated a phase transition at TC ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO2. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.

Comparative study of the structural and optical properties of epitaxial CuFeO2 and CuFe1−xGaxO2 delafossite thin films grown by pulsed laser deposition methods

“…[11] and [31]. Inspection of the Tauc-plot for indirect transitions (not shown) revealed a strong singular absorption edge initiated at 1.0eV which was again in agreement with [13][14][15].…”

“…Details of the experimental setup and procedure have been described elsewhere [13]. For the multilayer structure, a buffer layer of 9 monolayers (3 nm) of …”

“…Additionally, the breaking of dipole forbidden transition mechanisms is thought to emerge from Fe-3d states positioned within the forbidden regions of the crystalline structure [12]. Empirical testing has revealed strong absorption edges determined in the near infrared region between 1.1eV and 1.3 eV [13,15], the mid-visible region between 1.6eV and 2.0 eV [14][15], with higher energy band to band optical transitions also apparent for the blue-ultraviolet region between 3.0 and 3.4 eV [15]. There are also reports of direct absorption edges located at 1.6eV, with further absorption edges in the visible region at 2.0eV -2.4eV with variable high energy absorption edges approaching the UV region typically between 3.1-3.8 eV, showing both direct and indirect characteristics from Tauc-gap analysis [16].…”

Optical spectroscopy of nanoscale and heterostructured oxides

“…The absorption edge for CuFeO2 is even lower in energy than the doped structures with a first pronounced peak around 0.75 eV and a second peak near 1.25 eV, agreeing with earlier bandgap measurements. 35,72,77 At or near 5% Fe doping, the localized strain on the system from individual…”

“…This suggests the onset of a band edge. CuFeO2 is known to have an indirect bandgap at 1.15 eV 35,72,77.…”