Magnetic and structural studies of core/shell manganese oxide nanoparticles fabricated by inert gas condensation

Bah, Mohamed
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University of Delaware
Manganese oxide core/shell nanoparticles were prepared in an inert gas condensation system. X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM) studies revealed that the core consisted mainly of MnO which is ferromagnetic (FM) whereas the shell is a mixture of Mn2O3 and Mn3O4, both ferrimagnetic (FiM), with bulk Curie temperature (TC) of 39 K and 42 K, respectively. This results in an inverted core/shell structure. Both of these characteristic temperatures were found to be higher than their bulk counterpart, with TC = 46K and Néel temperature (TN) =150K. A high coercivity field (HC) of 20 kOe and an exchange bias field (HEB) of 200 Oe were observed from the magnetization measurements performed using a physical property measurement system (PPMS). High saturation magnetization, 10.67 emu/g, persistent magnetic moment above the TN presumably originating from the short-range spin correlation and other unusual behavior of the exchange bias (EB) and hysteresis loop are observed.