Mössbauer and optical investigation of Co3−x Fe x O4 thin films grown by sol–gel process

Abstract

Structural transformation and the related variation in magnetic and optical properties of Co 3−x Fe x O 4 thin films grown by a sol-gel method have been investigated as the Fe composition varies up to x=2. The normal spinel phase is dominant below x=0.55 and the inverse spinel phase grows as x increases further. Conversion electron Mössbauer spectroscopy (CEMS) measurements indicate that the normal spinel phase have octahedral Fe 3+ ions mostly while the inverse spinel phase contain octahedral Fe 2+ and tetrahedral Fe 3+ ions. For higher Fe composition (x >1.22), Co 2+ ions are found to substitute the octahedral Fe 2+ sites. The measured optical absorption spectra for the Co 3−x Fe x O 4 films by spectroscopic ellipsometry support the CEMS interpretation.

Blue pigments based on CoxZn1−xAl2O4 spinels synthesized by the polymeric precursor method

“…Sales et al [23] investigating powders with the composition 3(Al 1.95 Co 0.025-Ti 0.025 O 3 )$2SiO 2 , heat treated at 995 C for 1 h, found peaks at 510 nm, 575 nm and 618 nm. The position of the bands I, II and III in the present paper, 550, 580 and 620 nm, generally agrees with the values disclosed in the literature [22,24].…”

“…Kim et al [24] studied the Co 3Àx Fe x O 4 system and reported three visible peaks at 1.65 eV (752 nm), 2.4 eV (517 nm) and 2.8 eV (443 nm). The first peak was assigned to a t 2g (Co 3þ ) / t 2 (Co 2þ ) dd charge transfer (CT) transition, from the d(t 2g ) states of the octahedral Co 3þ ion to the d(t 2 ) states of the tetrahedral Co 2þ ion.…”

Alloying of Fe3O4 and Co3O4 to develop Co3xFe3(1−x)O4 ferrite with high magnetic squareness, tunable ferromagnetic parameters, and exchange bias

“…The additional hematite phase in chemical routed Co 3x Fe 3(1Àx) O 4 samples was also reported for low Co content [17,21]. This is due to doping effects of Co ions in Fe 3 [24,26]. This structural transformation from inverse spinel (for low Co content) to normal spinel (for high Co content) is consistent to the results of Mössbauer spectroscopy [24] and FTIR spectroscopy [19].…”

“…This is due to doping effects of Co ions in Fe 3 [24,26]. This structural transformation from inverse spinel (for low Co content) to normal spinel (for high Co content) is consistent to the results of Mössbauer spectroscopy [24] and FTIR spectroscopy [19]. Room temperature magnetic properties in low field regime (field up to ±16 kOe) were studied using VSM (Lakeshore 7404, USA).…”

Black and green pigments based on chromium–cobalt spinels

“…CoCr 2 O 4 and Co 3 O 4 are normal cubic spinels usually synthesized by solid state reaction for application in the pigment production [1,2]. Oxides and chromites have also been reported as active materials in catalysis, magnetic compounds and substrates for thin film growth [3][4][5][6][7][8][9]. The variety of oxidation states, the different host lattices in which chromium or cobalt can be found and the variety of synthesis routes explain both the color versatility and the different properties associated with these cations.…”