Tunable heat generation in nickel-substituted zinc ferrite nanoparticles for magnetic hyperthermia.

We report a high-performance magnetic nanoparticle as a hyperthermic agent under low applied field and frequency. CTAB (cetyltrimethylammonium bromide)-coated Ni Zn FeO nanoparticles of average particle size < 25 nm with various stoichiometric ratios were successfully synthesized using a co-precipitation technique. Characterization results indicate a close interaction of CTAB ions with the surface metal ions resulting in a cation distribution deviating from their equilibrium positions. Magnetic measurements were done at 300 K and 5 K using a superconducting quantum interference device. Saturation magnetization gradually increases with increasing substitution of Ni ions with Zn ions, attributed to the cation distribution and high super-exchange interaction between the A- and B-sites. The average size of the nanoparticles is estimated to be <10 nm with a magnetically dead layer (>1 nm @ 300 K), reflecting the effect of CTAB coating on the surface of the nanoparticles. The magnetocrystalline anisotropy ( ), obtained from the law of approach to saturation, is inversely proportional to the value. The increasing incorporation of Ni ions in the lattice system is found to influence various structural parameters, which is reflected in the magnetic performance of the nanoparticles. A specific absorption rate of 347 W g and intrinsic loss power of 4.6 nH m kg was attained with a minimal concentration of 2 mg ml in a very short time period of 1.5 min in NiZnFeO nanoparticles.