Structures and magnetic properties of the Co7Hf melt-spun ribbons

Co7Hf ribbons have been prepared by melt spinning technique. The effects of wheel speeds on the Structures and magnetic properties were investigated. At wheel speed of 35 m/s, the Co7Hf ribbons show the best intrinsic coercivity, remanence and maximum energy density, 2.0 kOe, 53 emu/g and 4.7 MGOe, respectively. XRD and TEM results show that Co7Hf ribbons are mainly composed of Co7Hf phase and Co phase. DSC and TEM results show that amorphous phase appeared at high wheel speed. The grain size refinement and the formation of amorphous phase were the main reasons for the changes of magnetic properties. Meanwhile, the excellent high temperature stability of Co7Hf ribbons was observed. In range of 27-500 degrees C, the temperature coefficients of remanence (alpha) and coercivity (beta) of Co7Hf ribbons are 0.11%/degrees C, -0.19%/degrees C, respectively.