Structural, Magnetic, and Transport Properties of MnNiGa Ribbon

The magnetic properties and the existence of spin reorientation have been systematically investigated in MnNiGa ribbons. The thermomagnetic curve reveals that as-spun and annealed ribbons undergo a two-step magnetic structural transformation and the magnetic properties of the annealed ribbons are improved. The splitting behaviour of zero-field-cooled and filed-cooled (ZFC-FC) curve shows that the ribbon has occurred a spin reorientation transformation. The ZFC and isothermal magnetization curves tested by changing the direction of the magnetic field illustrate the existence of magnetic anisotropy, and the direction of  H// is easily magnetized. In the direction of easy magnetization, the value of magnetic entropy is about 1.54 J/kg K. The easy magnetization direction is proved to be in-plane by the decrease of the magnetic domain phase shift. It is clear that the magnetoresistance is negative in all temperature ranges and the nonlinear variation at low fields accounts for the presence of spin reorientation. The variation of Hall resistance curve in a low magnetic field reflects the existence of an abnormal Hall effect.