Controllable synthesis and magnetic properties of cubic and hexagonal phase nickel nanocrystals

Magnetic properties and controllable synthesis of cubic and hexagonal phase nickel nanocrystals are discussed. The controllable synthesis is based on thermal decomposition of a Ni oleate complex in a dodecylamine and octadecene system. Crystal phase control of Ni NCs has been realized by adjusting the growth environment and growth dynamics of Ni NCs. Pure cubic and pure hexagonal phase Ni NCs can be easily obtained by adjusting the concentration of the dodecylamine and the growth dynamics. The as-synthesized sample was characterized using XRD, TEM, HRTEM, and magnetic measurements. Experimental results show that the concentration of dodecylamine, the heating rate, and the reaction temperature are the key factors for controlling the phase structure of Ni NCs. Magnetic measurements show that both the cubic and hexagonal phase Ni NCs possesses ferromagnetic properties, but the magnetic properties of the cubic phase Ni NCs are stronger than that of the hexagonal phase.