Speakers
Description
Nanocomposites have gained interest in current research because of the unique properties and scientific significance it has shown[1-2].It was found that composites that comprise of ferrimagnetic(FiM) and antiferromagnetic(AFM) materials exhibit fascinating magnetic phenomena including proximity effect and exchange bias[2,3].These phenomena manifest due to strong exchange coupling between FiM and AFM material[3].Cu$_{2}$O is an AFM material with a monoclinic crystal structure,that undergoes two magnetic transitions at T$_{N1}$=213K and T$_{N2}$=230K[3].The novel properties of Cu$_{2}$O such as weak FM and superparamagnetic(SPM) are attributed to size effects[4].CoCr$_{2}$O$_{4}$ is a FiM material with a cubic crystal structure, exhibiting three magnetic transitions at TC=93K,Ts=26K,and TL=15K[5].Ts is the temperature associated with the formation of a magnetic conical spin state anomaly due to the spiral ordering causes a multiferroic in a material[5].TL is the temperature associated with the transition from the commensurate to the incommensurate magnetic phase where spiral orderings are fully developed[5]. CoCr$_{2}$O$_{4}$ is a well-studied ternary multiferroic spinel with a conical structure and it manifests itself below Ts.CoCr$_{2}$O$_{4}$ exhibit an exchange bias without mixing with different magnetic material[5]. Rath et al.[7] investigated the magnetic properties of CoCr$_{2}$O$_{4}$ nanoparticles with average size 10-12 nm.SPM behaviour was observed,with a blocking temperature between 50-60K[7].The disordered spin at the surface and distribution of nanoparticle sizes play important roles in the observation of SPM behavior in a material[7].In order to expand on these observations, the present study considers a CoCr$_{2}$O$_{4}$/Cu$_{2}$O composite that was synthesized using two-step methods.The initial step uses the sol-gel method[6] to synthesize the CoCr$_{2}$O$_{4}$ nanoparticles.The sample was calcined at 400 $^{o}$C for 2 hours and characterized using different techniques. Single-phase CoCr$_{2}$O$_{4}$ formed,with the particle size of 12.47±0.50nm, and the particles undergo a FiM from a PM transition at T$_{C}$=98K.T$_{s}$ and T$_{L}$ were not observed due to the weak Cr-Cr interaction and size effect[8].The following step involves co-precipitation to synthesize the CoCr$_{2}$O$_{4}$/Cu$_{2}$O composite, with cetyltrimethylammonium bromide (CTAB) used as a capping agent.The sample was again calcined at 400 °C to adjust the particle size [9].X-ray diffraction (XRD) results confirm the formation of multiphases associated with the Fd-3m and,C12/c1 space groups[4,6] related to the crystal structure of CoCr$_{2}$O$_{4}$ and,Cu$_{2}$O, respectively.The average crystallite size was estimated to be less than 43±1nm.Transmission electron microscopy(TEM) was employed to determine the average particle size and morphology.Both CoCr$_{2}$O$_{4}$ and CoCr$_{2}$O$_{4}$/Cu$_{2}$O particles reflected non-uniform sizes and spherical shapes. Magnetic measurements were done using a vibrating sample magnetometer(VSM).The magnetic susceptibility as a function of temperature shows a PM to FiM transition at 94K for composite.The magnetic hysteresis loop shows SPM behaviour at 75K,while no exchange bias was observed at low temperatures for the composite.
[1] R. Yassine,et al.Ceram. Int. 48.10(2022):14825-14838.
[2] T. Woldu,et al. J. Alloys Compd 691(2017)644-652.
[3] P.K. Manna,et al. Phys. Rep. 535.2(2014):61-99.
[4] R.S. Bhalerao-Panajkar,et al. Solid State Commun. 151.1(2011):55-60.
[5] Y. Yamasaki,et al. Phys. Rev. Lett 96.20(2006):207204.
[6] S. Goswami,et al. J. Alloys Compd (2021):161916.
[7] C. Rath,et al. J. Supercond. Nov. Magn. 24.1(2011): 629-633.
[8] D. Zákutná,et al.Phys. Rev. B 100.18(2019):184427.
[9] S. Naz, Sumaira,et al. J. Saudi Chem. Soc. 20.5(2016):585-593.
Level for award;(Hons, MSc, PhD, N/A)?
PhD
| Apply to be considered for a student ; award (Yes / No)? | YES |
|---|
