Effect of Soft Phase on Magnetic Properties of Bulk Sm–Co/$\alpha$–Fe Nanocomposite Magnets

Abstract

Bulk Sm-Co/α-Fe nanocomposite magnets were fabricated by high energy ball milling and subsequent quick hot-pressing. Three different parameters were investigated which are soft phase content, type, and distribution. The effect of Fe soft phase content on the magnetic properties of the final bulk samples was examined. Increasing the Fe content significantly increased the saturation magnetization but at the cost of reduced coercivity. The optimum Fe addition for the highest maximum energy product was determined to be 15 wt% under the present processing conditions. Besides pure Fe a Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">49</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">49</sub> V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> powder was also studied as a soft phase addition. The results indicated that FeCoV powder was more readily alloyed with the Sm-Co phase during the milling procedure. For the final bulk magnets, nanoscale Fe particles existed in Sm-Co matrix with pure Fe addition, but with Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">49</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">49</sub> V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> addition the soft phase particles were undetectable. Two methods for adding soft phase Fe into hard phase SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> were utilized. The investigation showed that milling Fe and SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> together resulted in a more uniformly distributed mixture of nanoscale soft phase particles, improved squareness of the demagnetization curves of bulk nanocomposite magnets, and higher (BH) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> as compared to blending Fe with SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> .