Date of Graduation

Fall 2022


Master of Science in Materials Science


Physics, Astronomy, and Materials Science

Committee Chair

Robert Mayanovic


I studied the effect of core size and metal concentration on the structural, morphological, and magnetic properties of NiO-based magnetic heterostructured nanocrystals (HNCs) generated hydrothermally. The NiO nanocrystals were created by a thermal decomposition technique, while the surrounding Mn and Co-based phases were created through a hydrothermal procedure, with core diameters ranging from 9.31 nm to 24.51 nm and total metal concentrations of 0.05 M and 0.08 M. The resulting inverted AFM-FiM NiO/CoMn2O4 bimagnetic systems make up the heterostructured nanocrystals. The magnetic HNCs were thoroughly characterized using XRD, SEM-EDX, TEM, PPMS magnetometry, and XPS analysis. Investigations into the structure of the HNCs indicated that they were mostly faceted and pseudospherical, with topotaxially formed CoMn2O4 spinel overlayers shell/nanoislands. Magnetic measurements show that as core particle size decreases, coercivity, exchange bias, and remanent magnetization values increase significantly. At 5 K, the 19 nm core-sized sample exhibited the greatest exchange bias of 1.48 KOe and coercivity of 3.47 Koe. Improving exchange bias depends on a number of factors, including interface crystallinity, surface effect, and uncompensated spins. Finally, the XPS spectra delineates the surface chemical composition of the bimagnetic heterostructured nanocrystals. This work on the core-shell system’s synthesis technique and on understanding the large exchange bias effect could lead to the use of heterostructured nanoparticles in magnetic devices and biomedical applications.


heterostructured nanocrystals, hydrothermal, exchange bias, coercivity, spinel structure, magnetic anisotropy, XPS

Subject Categories

Nanoscience and Nanotechnology | Other Materials Science and Engineering


© Farhan Ishrak

Available for download on Sunday, January 05, 2025

Open Access