Electron spin resonance and induction heating studies of zinc substituted (Mn, Co) ferrite nanoparticles for potential magnetic hyperthermia applications

Abstract

This study presents an investigation on the various spin relaxation processes taking place at X-Band microwave energy in Zn substituted MnFe2O4 and CoFe2O4 and their induction heating studies. The material properties of these citric acid assisted sol-gel synthesized nanoparticles have been explored using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscope, Vibrating sample magnetometer (VSM) and Electron spin resonance spectroscopy. XRD and Rietveld refinement confirm the face centered cubic spinel structure of the synthesized samples, which is further supported by the observation of absorption bands characteristic of the spinel ferrites in the FTIR spectra. The remanence, coercivity and effective magnetocrystalline anisotropy values from VSM studies show lower value with zinc substitution which is desirable for biomedical application. Various spin resonance parameters like gyromagnetic ratio, peak to peak linewidth, resonance field, spin-lattice and spin-spin relaxation times have been calculated. The induction heating studies of the samples in an alternating magnetic field have been carried out using a field strength of 4.58 × 109 Am-1s-1. All the investigated MNPs are able to raise the temperature to the therapeutic limit of 42–45 °C. The specific absorption rate (SAR) which describe the heating potential of the MNPs is calculated using four different concentrations of each sample - 5 mg mL-1, 10 mg mL-1, 15 mg mL-1 and 20 mg mL-1. SAR values are found to decrease with increase in concentration and achieve the highest value of 303 W/g for Co0.5Zn0.5Fe2O4 nanoparticles with 5 mg mL-1 concentration. The ability of the MNPs to give rise to the therapeutic temperature points toward their suitability as an effective heat mediator in magnetic hyperthermia treatment of cancer.