  The magnetic properties of carbon nanotube encapsulated nickel nanowires
(C.E. nanowires of diameter ~ 10 nm), and its comparison to other forms of Ni
are carried out in this work. The saturation magnetization (M_s) and coercivity
(H_c) for C.E. nanowires are 1.0 emu/g and 230 Oe. The temperature dependence
of coercivity follows T^0.77 dependence indicating a superparamagnetic
behavior. The field-cooled and zero-field-cooled plots indicate that the
blocking temperature (T_B) ~ 300 K. These altered magnetic properties of C.E.
nanowires are mainly due to the nanoscale confinement effect from carbon
nanotube encapsulation. The shape and magnetic environment enhance the total
magnetic anisotropy of C.E. nanowires by a factor of four.
