We prepared ultra thin film structure of Si(100)/ $SiO_2$(200 nm)/Ta(5 nm)/Ni$_{80}$Fe$_{20/(l～15 nm)}$Ta(5 nm) using an inductively coupled plasma(ICP) helicon sputter. Magnetic properties and cross-sectional microstructures were investigated with a superconduction quantum interference device(SQUID) and a transmission electron microscope(TEM), respectively. We report that NiFe films of sub-3 nm thickness show the B$_{bulk}$ = 0 and B$_{surf}$=-3 ${ imes}$ 10$^{-7}$(J/$m^2$). Moreover, Curie temperature may be lowered by decreasing thickness. Coercivity become larger as temperature decreased with 0.5 nm - thick Ta/NiFe interface intermixing. Our result implies that effective magnetic properties of magnetoelastic anisotropy, saturation magnetization, and coercivity may change abruptly in nano-thick films. Thus we should consider those abrupt changes in designing nano-devices such as MRAM applications.