LAUSR

Abstract In this work, we report the structural and magnetic properties of nanocrystalline Cu 1−x Zn x Fe 2 O 4 mixed ferrites synthesized using novel combustion method. The prepared samples are spinel structured and the secondary phase α-Fe 2 O 3 is also present in CuFe 2 O 4 . The size of the crystallites ranges between 9.6 nm and 31 nm and the lattice constant increases from 8.342 A to 8.435 A. The FTIR absorption bands of CuFe 2 O 4 are observed at 571 cm −1 and 409 cm −1 for tetrahedral and octahedral sites, respectively. These bands are shifting to 547 cm −1 and 397 cm −1 for Zn substitution. Raman spectra show the change in local environment of tetrahedral and octahedral interstitial sites with Zn. The FE-SEM images show that the prepared samples are nano sized and the substitution of Zn decreases the agglomeration. The magnetic study reveals that the saturation magnetizations initially increases from 21.45 emu/g (x = 0) to 44.16 emu/g (x = 0.2) and then decreases at 300 K. The superparamagnetic behavior is observed for samples of x ≥ 0.4 concentration. The temperature dependent zero field cooled and field cooled magnetic measurements confirm the superparamagnetic nature and the observed blocking temperature decreases from 120.4 K to 32.3 K. The hysteresis curves measured at 20 K show the coercivity and it varies from 663 Oe to 70 Oe for increasing Zn content.