Magnetic properties of Nanocrystalline Co and Ni synthesized via superhydride reduction route

Nanocrystalline and surface functionalized Co and Ni were successfully synthesized via superhydride reduction route by using oleic acid and oleylamine as capping agents. Fourier transform infrared (FTIR) study of as-prepared materials confirms the presence of organic capping layer on the surface of nanoparticles. Phase purity and crystallite sizes of the materials were ascertained from X-ray diffraction (XRD) patterns. Co crystallizes in the mixture of hexagonal close packed (hcp) and face centered cubic (fcc) phases with crystallite size of 15 nm whereas Ni crystallizes in face centered cubic (fcc) phase with crystallite size of 35 nm. Transmission electron microscopy (TEM) studies confirm the fine particle nature of the materials and spherical shape morphologies with TEM particle sizes equal to 20 nm and 25 nm for Co and Ni, respectively. Room temperature magnetic studies show ferromagnetic behavior of the materials. The values of saturation magnetization, coercivity and magnetic particle size for Co are 64 emu/g, 436 Oe and 10 nm, respectively whereas those for Ni are 29 emu/g, 148 Oe and 20 nm, respectively. Dipolar interactions among the particles at lower temperatures have been studied from field cooled (FC) and zero field cooled (ZFC) curves. Low temperature magnetic study shows ferromagnetism with dipolar interactions in the materials up to 300 K and some sort of magnetic phase transitions below 20 K.