Magnetic behavior of polymorph composite nickel titanate nanofibers

Abstract

Polymorph (spinel/ilmenite) composite nanofibers of nickel titanate (NTO) were prepared by a sol–gel assisted electrospinning process followed by pyrolysis using the styrene–acrylonitrile copolymer as a precursor at three different pyrolysis soaking temperatures (i.e. T = 773, 973, and 1173 K). The magnetic behavior of these composite NTO nanofibers was studied under isothermal and non-isothermal conditions in the temperature range of 20–300 K. The magnetic parameters such as coercivity (H_c), remanence (M_r), and saturation magnetisation (M_s) were found to be strongly dependent on T. The highest H_c and M_r were observed for NTO nanofibers developed at 973 K, which have a mosaic structured morphology with spinel and ilmenite NTO crystallite sizes of ∼39 nm and ∼24 nm, respectively. On the other hand, the highest M_s and switching field distribution were observed for mosaic structured NTO nanofibers having smaller crystallites (∼13 nm and 24 nm for spinel and ilmenite NTO, respectively, with high inter-particle distance and high porosity) developed at 773 K, which are also rich in spinel NTO content. The correlation between the variation in magnetic behavior and structural/morphological features of NTO nanofibers is useful for NTO-based soft magnetic and multiferroic applications.