Magnetic properties of ultrafine Co particles

Co fine particles with a size in the range of 50 - 350 Å have been prepared by the vapor deposition technique. Argon gas at pressure of 1 - 30 torr was used to provide the inert atmosphere for particle preparation. Particles were passified using an air-argon mixture before exposing them to atmosphere, in order to create a protective oxide layer on their surface. X-ray spectroscopy and selected area diffraction (SAD) data matched those of fcc Co and and CoO. The size and morphology of the particle were studied using transmission electron microscopy (TEM). The magnetic properties were measured with a SQUID magnetometery the temperature range of 4.2 - 300 K and in fields upto 55 kOe.