Structural, magnetic, optical, and magneto-optical properties of CoFe2O4 thin films fabricated by a chemical approach

doi:10.1016/j.materresbull.2019.05.002

Materials Research Bulletin

Volume 117, September 2019, Pages 96-102

https://doi.org/10.1016/j.materresbull.2019.05.002 Get rights and content

Highlights

•
Homogeneous thin films of CoFe₂O₄ were fabricated using cost effective chemical approach.
•
Chemical approach has been found to provide attractive alternative compared to other deposition methods.
•
Chemical approach provides smooth films with good saturation and remanent magnetization values and optical properties.
•
Tuning the chemical composition could lead to more effective fabrication and higher quality crystalline tuneable thin films.
•
Improved magnetic, optical, and magneto-optical properties could be possible by tuning the chemical composition.

Abstract

Homogeneous, smooth, and partially transparent nanocrystalline thin films of CoFe₂O₄ were fabricated using a chemical solution approach with additional annealing for 2 h in a temperature range of 300 °C to 600 °C. Structural properties investigated by X-ray diffraction showed a single-phase spinel structure with a random crystallographic orientation for samples annealed above 400 °C. The ferromagnetic nature of prepared films was established from combined substrate with film hysteresis loops measured using a vibrating sample magnetometer. Optical and magneto-optical spectroscopic measurements revealed an improvement in the structural quality of the films after annealing up to 600 °C.

Graphical abstract

High quality homogeneous CoFe₂O₄ thin films have been prepared by cost effective chemical solution approach. After annealing at 500 °C or more, they show inverse spinel structure, saturation magnetization comparable with the bulk crystal value, and overall improvement in their crystalline properties. With increasing annealing temperature, the samples also show overall improvement in their optical and magneto-optical response.

Introduction

Development of electronic and optoelectronic technologies focuses on continuously smaller devices and their feature size, which can show excellent performance improvement and lower power consumption. Generally, this also implies necessary changes to the materials used, or their deposition process. In most cases, fabrication is attuned with high levels of integration that often include ferrite thin films or ferromagnetic composite devices [1,2]. Progress in miniaturization and integration of microwave devices is influenced by the ability to fabricate thin films with high tunability of their physical properties, especially for lower loss. The structure-property correlation of ferrite thin films depends on their composition, preparation conditions, particle size, and morphology. The magnetic properties of ferrite thin films are also strongly dependent on their nanostructure and deposition methods [3,4]. Data storage based on ferromagnetic thin films made a revolutionary impact on paperless technologies, so this area of research has been attracting potential interest due to its applications for even higher storage capacity. Cobalt ferrite has specifically attracted attention because of its strong magneto-crystalline anisotropy and high Curie temperature in several technological applications such as high-density recording media, spin filtering and multiferroics [[5], [6], [7]].

Nanoscale magnetic thin film growth and fabrication have been performed using various methods such as electrodeposition [8], non-aqueous solution [9], sol-gel [10,11], sputtering, molecular beam epitaxy, pulsed laser deposition [12], etc. Recent results in the synthesis of periodic nanoporous cobalt ferrite thin films have exhibited tunable room temperature ferromagnetism and their magnetic properties dependency on crystallite size of the ferrite. Very smooth thin films of nanoferrite materials have also become attractive for research and development because of their potential magneto-optical applications [13]. For many investigations using optical and magneto-optical effects, thin films are known to be homogeneous, continuous, and transparent below bandgap. They are also partially transparent, depending on their thickness, above the bandgap energy. High-quality ferrite thin films are essential for most of the magnetic devices that require low magnetic losses and tailored magnetic properties [14].

Magnetic properties of ferrite films are highly sensitive to crystalline disorder if compared with other metal films, such as permalloy ones. Soft magnetic thin films of cobalt ferrite are employed as high magnetostrictive materials for stress, pressure, and torsion sensors, catalysts or gas/humidity sensors [15], and microactuators [16]. The objective of this work is to synthesize and fabricate high-quality CoFe₂O₄ crystalline thin films with industry applicable properties using dip-coating into a chemical solution. Their structural, magnetic, optical, and magneto-optical properties have been analyzed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometry (VSM), Ellipsometry, and Magneto-Optical Kerr Effect (MOKE) spectroscopy.

Section snippets

Experimental details

Used ingredients, Fe(NO₃)₃.9H₂O (99.9%), Co(NO₃)₂.6H₂O, ethylene glycol, and citric acid, were procured by Sigma Aldrich. Stoichiometric amounts of the metal salt precursors Fe(NO₃)₃.9H₂O (2.02 g) and Co(NO₃)₂.6H₂O (0.7275 g) were dissolved in 25 ml of ultrapure water from a Millipore Elix A3-MilliQ system (MilliQ, Germany) to get a clear yellowish-brown colored solution. An aqueous solution of citric acid (6.3 g in 100 ml) was added to the precursor solution under constant magnetic stirring

Methods

X-ray diffraction patterns were recorded under Co Kα irradiation (λ =1.789 Å, 35 kV, 25 mA) using a Bruker D8 Advance diffractometer (Bruker AXS) equipped with a fast position sensitive detector VÅNTEC 1. Measurements were carried out in reflection mode using Bragg-Brentano geometry in the angular range of 3–100°.

SEM micrographs of the annealed thin films were obtained with a Quanta 650 FEG (Thermo Fisher Scientific) scanning electron microscope, operated in the field emission mode under low

Results and discussion

XRD patterns of CoFe₂O₄ thin films, annealed at temperatures 300 °C, 400 °C, and 500 °C are shown in Fig. 1. The diffraction pattern for the sample annealed at 300 °C exhibits an incomplete crystalline phase as the critical temperature required to fully decompose the precursors incorporated in prepared layers is above 300 °C. However, improvement in the crystalline structure with the increase of annealing temperature is shown from case (a) to case (c) in Fig. 1. The annealed CoFe₂O₄ films are

Conclusion

Homogeneous high-quality nanocrystalline thin films of CoFe₂O₄ were fabricated using a cost-effective chemical solution approach based on sol-gel and dip-coating. The films annealed above 500 °C exhibited crystalline phase with inverse spinel structure. The prepared films were ferrimagnetic and increased their saturation magnetization with annealing temperature. In the case of the inverse spinel structure, the alignment is ferrimagnetic (canted spins) at room temperature. The optical

Acknowledgments

The authors acknowledge support from the Postdoc II project opportunity for young researchers Reg. No. CZ.1.07/2.3.00/30.0055, the ERDF in the IT4Innovations national supercomputing center - path to exascale project (CZ. 02.1.01/0.0/0.0/16_013/0001791) within the OPRDE, the MATFUN project (CZ. 02.1.01/0.0/0.0/15_003/0000487), the GAČR18-22102S and the Student Grant Competition of the Czech Ministry of Education, Youth and Sports, SP2018/43 and SP2018/96. The authors acknowledge Prof. Vladimír

References (34)

D.M. Schleich et al.
Mater. Res. Bull.
(1995)
Z. Šimša et al.
J. Magn. Magn. Mater.
(2002)
S.L. Darshane et al.
Ceram. Int.
(2009)
P. Guo et al.
Colloids Surfaces A: Physicochem. Eng. Aspects
(2012)
D.S. Mathew et al.
Chem. Eng. J.
(2007)
J. Teillet et al.
J. Mag. Mag. Mater.
(1993)
S. Ouaissa et al.
Phys. Procedia
(2015)
E. Marsan et al.
IEEE
(2005)
P. Guo et al.
Langmuir
(2013)
S. Srikanth et al.
J. Mater. Chem.
(2011)

L.-X. Yang et al.

J. Nanometer

(2013)

J.A. Paulsen et al.

IEEE Trans. Magn.

(2003)

R.E. Lu et al.

J. Mater. Chem. C

(2014)

S.D. Sathaye et al.

J. Mater. Sci.

(2003)

S. Diodati et al.

Nano Res.

(2014)

J.W. Long et al.

J. Am. Chem. Soc.

(2004)

A. Demir et al.

J. Inorg. Organomet. Polym. Mater.

(2014)

Cited by (19)

Improved photocatalytic performance in Ce<sup>3+</sup> doped CoFe<inf>2</inf>O<inf>4</inf> nanoparticles by modifying structural, optical, and magnetic properties
2024, Materials Science in Semiconductor Processing
In recent research, semiconductive magnetic nanomaterials have gained significant attention for their potential in photocatalytic applications, primarily due to their ease of recoverability. This study focuses on the successful synthesis of CoCe_xFe_2-xO₄ nanoparticles, where the variable x (ranging from 0 to 0.20) introduces Ce³⁺ ions. The inclusion of Ce³⁺ ions induces noteworthy changes in the structural, optical, microstructural, magnetic, and photocatalytic properties of CoFe₂O₄ nanoparticles. Various analytical techniques, including x-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, photoluminescence, transmission electron microscopy, vibrating sample magnetometry, and electron paramagnetic resonance spectroscopy, were employed to investigate these effects comprehensively. The research delves into the photocatalytic degradation of rhodamine B under visible light irradiation, exploring the impact of different elemental compositions, catalyst quantities, irradiation durations, and initial rhodamine B concentrations on the decolorization process.
Tailoring structural, optical, and magnetic properties of Y<sup>3+</sup> doped CoFe<inf>2</inf>O<inf>4</inf> nanoparticles to enhance photocatalytic activity
2024, Ceramics International
In recent times, there has been a significant focus on semiconductive magnetic nanomaterials due to their potential in photocatalytic applications, primarily because of their easy recoverability. In this work, CoY_xFe_2-xO₄ nanoparticles (with varying x values: 0, 0.05, 0.10, 0.15, and 0.20) were successfully synthesized. The incorporation of Y³⁺ ions induced notable transformations in the structural, optical, microstructural, magnetic, and photocatalytic properties of CoFe₂O₄ nanoparticles. Analytical techniques such as x-ray diffraction, fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, transmission electron microscopy, vibrating sample magnetometry, and electron paramagnetic resonance spectroscopy were employed to investigate these effects. The investigation into the photocatalytic degradation of methylene blue (MB) under ultraviolet light irradiation was carried out. The influence of distinct elemental compositions, catalyst quantities, irradiation durations, and initial methylene blue concentrations on the decolorization process was assessed.
Effect of annealing temperature on phase transitions and photo-Fenton catalytic activity of CoFe<inf>2</inf>O<inf>4</inf> nanopowder
2023, Journal of Physics and Chemistry of Solids
In this work, the hydrothermal technique was used to synthesize cobalt ferrite (CFO) magnetic nanoparticles. Then, the as-prepared CFO sample was annealed at four different temperatures (600, 700, 800, and 900 °C) to study the effect of the annealing temperature on the crystallite growth, magnetic properties, phase transitions, and photo-Fenton catalytic activity of CFO powder samples. The properties of CoFe₂O₄ were characterized by X-ray powder diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, Brunauer–Emmet–Teller analysis, vibrating sample magnetometry, and catalytic tests. The results showed that the annealing temperature significantly affected the phase structure, crystallite size, morphology, specific surface area, magnetic properties, and catalytic activity of CFO powder samples. The calcined CFO sample had higher catalytic activity than the as-prepared CFO. At the annealing temperature of 600 °C (CFO-600), the catalytic efficiency and rate constant of this material for the degradation of methylene blue under ultraviolet A irradiation for 60 min reached 95% and 3.16 h⁻¹, respectively, in the presence of oxalic acid as a potential oxidizing agent. We also found that a higher number of Fe³⁺ ions occupying octahedral sites on the CFO surface resulted in a higher activity of the CFO photo-Fenton catalyst. In particular, the CFO-600 powder with excellent magnetic properties exhibited a good recycling catalytic performance. The present material holds promise as a potential practical candidate for treating pollution caused by organic dyes and limiting secondary contaminants released during the photocatalyst process.
Structural, morphological, and optical properties of Co- substituted Zn<inf>2</inf>SiO<inf>4</inf> nanopowders prepared by a hydrothermal-assisted sol-gel process
2022, Materials Chemistry and Physics
Citation Excerpt :
Transition metal-based materials have attracted much attention thanks to their interesting optical, electrical, structural, and electronic properties [1–5].
Cobalt-substituted zinc orthosilicate pigments were obtained by pyrolysis of precursors synthesized by a convenient hydrothermal-assisted sol-gel process without using any toxic or expensive chemical (e.g., silicon alkoxides). XRD investigation confirms that the Co²⁺ ions are successfully incorporated into the Zn₂SiO₄ crystal. Rietveld refinement data reveals that unit-cell parameters increase with Co-content in Zn_2-xCo_xSiO₄ solid-solutions. The homogeneous pigments are composed of largely agglomerated primary particles having a size less than 70 nm. The UV–visible spectroscopy shows that the blue color of pigments is caused by the presence de Co²⁺ in tetrahedral sites of Zn²⁺. The colorimetric parameters indicate that a blue pigment could be achieved with the only x = 0.05. A content of less than 5 wt% of the prepared pigments gives a deep blue hue to ceramic glazes. Cobalt-substituted Zn₂SiO₄ pigments exhibit high coloring performance and a relatively less cobalt content, which make them promising pigments for ceramic tiles.
Accurate band gap determination of chemically synthesized cobalt ferrite nanoparticles using diffuse reflectance spectroscopy
2021, Advanced Powder Technology
Optical band gap of cuboidal Cobalt ferrite (CoF) Nanoparticles (NP), synthesized using wet chemical method, was accurately determined, by combining Diffuse Reflectance Spectroscopy (DRS) of the nanopowder, Schuster-Kubelka-Munk (SKM) formalism and the application of a detailed band gap estimation algorithm, using which absorption onsets and corresponding base line segments from the Tauc plots were precisely identified. Structural and compositional characterizations such as XRD, FE-SEM, TEM and EDX, were used to conclude that the NP exhibited cubic crystal structure with an average crystallite size of 14 nm. The values of indirect and direct band gaps were calculated to be 0.79 ± 0.01 eV and 1.5 ± 0.01 eV, respectively. The band gap shift for the nanocrystallites, from the bulk band gap, estimated using the effective mass model, came up to a value of 0.084 eV, which corresponded well to the experimentally obtained direct band gap of CoF NP. The direct and indirect band gap values were found to be well consistent with the partially inverse spinel crystal structure of the NP, emphasized using magnetization measurement.
An efficient and magnetically recoverable g-C<inf>3</inf>N<inf>4</inf>/ZnS/CoFe<inf>2</inf>O<inf>4</inf> nanocomposite for sustainable photodegradation of organic dye under UV–visible light illumination
2021, Environmental Research
Citation Excerpt :
Cobalt ferrite (CoFe2O4) is an inverse spinel oxide that comprises, large curie temperature, high adsorption capacity, better chemical stability, low toxicity, and moderate magnetization. The CoFe2O4 NPs play a key role in various applications such as cancer treatment (Colombo et al., 2012), supercapacitor (Sankar et al., 2015), photocatalysis (Jing et al., 2016), high-density recording media (Illa et al., 2019), and gas sensors (Khandekar et al., 2014) also. Recently, Kula Kamal Senapati et al. (2012) reported a magnetically separable CoFe2O4/ZnS nanohybrid for the UV-light-driven photodegradation MO dye.
Effective improvement of an easily recoverable photocatalyst is equally vital to its photocatalytic performance from a practical application view. The magnetically recoverable process is one of the easiest ways, provided the photocatalyst is magnetically strong enough to respond to an external magnetic field. Herein, we prepared graphitic carbon nitride nanosheet (g-C₃N₄), and ZnS quantum dots (QDs) supported ferromagnetic CoFe₂O₄ nanoparticles (NPs) as the gC₃N₄/ZnS/CoFe₂O₄ nanohybrid photocatalyst by a wet-impregnation method. The loading of CoFe₂O₄ NPs in the g-C₃N₄/ZnS nanohybrid resulted in extended visible light absorption. The ferromagnetic g-C₃N₄/ZnS/CoFe₂O₄ nanohybrid exhibited better visible-light-active photocatalytic performance (97.11%) against methylene blue (MB) dye, and it was easily separable from the aqueous solution by an external bar magnet. The g-C₃N₄/ZnS/CoFe₂O₄ nanohybrid displayed excellent photostability and reusability after five consecutive cycles. The favourable band alignment and availability of a large number of active sites affected the better charge separation and enhanced photocatalytic response. The role of active species involved in the degradation of MB dye during photocatalyst by g-C₃N₄/ZnS/CoFe₂O₄ nanohybrid was also investigated. Overall, this study provides a facile method for design eco-friendly and promising g-C₃N₄/ZnS/CoFe₂O₄ nanohybrid photocatalyst as applicable in the eco-friendly dye degradation process.

View all citing articles on Scopus

View full text

Structural, magnetic, optical, and magneto-optical properties of CoFe2O4 thin films fabricated by a chemical approach

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental details

Methods

Results and discussion

Conclusion

Acknowledgments

Mater. Res. Bull.

J. Magn. Magn. Mater.

Ceram. Int.

Colloids Surfaces A: Physicochem. Eng. Aspects

Chem. Eng. J.

J. Mag. Mag. Mater.

Phys. Procedia

IEEE

Langmuir

J. Mater. Chem.

J. Nanometer

IEEE Trans. Magn.

J. Mater. Chem. C

J. Mater. Sci.

Nano Res.

J. Am. Chem. Soc.

J. Inorg. Organomet. Polym. Mater.

Structural, magnetic, optical, and magneto-optical properties of CoFe₂O₄ thin films fabricated by a chemical approach