Superparamagnetic properties Ni–Zn ferrite for nano-bio fusion applications

Abstract Ni 0.7 Zn 0.3 Fe 2 O 4 nanoparticles were fabricated by a sol–gel method. Ni 0.7 Zn 0.3 Fe 2 O 4 powders annealed at 300 °C compose a spinel structure and behaved superparamagnetically, while annealed at 400 and 500 °C have typical spinel structure with ferrimagnetism in nature. The mean size of Ni 0.7 Zn 0.3 Fe 2 O 4 nanoparticle is about 11 nm. The hyperfine fields at 13 K for the tetrahedral ( A ) and the octahedral ( B ) patterns were found to be 499 and 523 kOe, respectively. Blocking temperature ( T B ) of Ni 0.7 Zn 0.3 Fe 2 O 4 nanoparticle is about 260 K. Also, temperature increased up to 43 °C within 7 min under AC magnetic field of 7 MHz.