Synthesis of Samarium-Cobalt Sub-micron Fibers and Their Excellent Hard Magnetic Properties.

High-throughput synthesis of Samarium-Cobalt sub-micron fibers with controlled composition and dimension was demonstrated by combining electrospinning and reduction-diffusion processes. The composition of fibers was readily varied (8 < Sm < 20 at.%) by adjusting precursor composition whereas the diameter of fibers was precisely controlled by varying electrospinning parameters (e.g., applied voltage, solution feed rate, temperature, and humidity) to reach single-domain size. X-ray diffraction patterns confirmed that single phase Sm2 Co17 fibers were synthesized when the metal precursor ratio (Sm3+ /(Sm3+ +Co2+ )) was precisely controlled at 10.6%, whereas mixed phases (i.e., Co-Sm2 Co17 or Sm2 Co17 -Sm2 Co7 ) were observed when the ratio is deviated from the stoichiometric. Magnetic saturation ( M s ) of the synthesized fibers monotonically decreased with an increased in Sm content. In contrast, coercivity ( H c i ) monotonically increased with an increase in Sm content.