Magnetic properties of nano-size Ni synthesized by the pulsed wire evaporation (PWE) method

Nano-crystalline Ni has been synthesized by a pulsed wire evaporation (PWE) method, and its abnormal magnetic properties in a magnetic ordered state have been characterized using high and low magnetic fields. It was found that particles with the size ranges from 20 to 80 nm has a mean crystalline size of 40 nm which might influence the magnetic hysterisis behavior. Neutron powder diffraction (NPD) and saturation magnetization results indicate the antiferromagnetic NiO phase in prepared powder exist below the detection limit of 1 wt.%. The shifted hysterisis loop and irreversibility of magnetization in a high field were observed in the magnetic-ordered state of Ni. The initial magnetization curve for Ni is started to overlap the hysterisis loop at applied field of 750 Oe. This irreversibility in a high field can be explained by the non-collinear behavior and the existence of the metastable states of the magnetization at the surface layer (or core) of the particle in the applied magnetic field due to decrease of particle size.