FeCo Coating on SmCo5 Nanochips by a Sonochemical Method

To study the influence of soft magnetic phase coating on magnetic properties of hard/soft phase nanocomposite materials, the coating of soft magnetic FeCo on hard magnetic SmCo₅ nanochips was performed via a sonochemical process. First, anisotropic hard magnetic SmCo₅ nanochips were prepared by surfactant-assisted high-energy ball milling in the presence of oleic acid as a surfactant and heptane as a solvent. Then, the soft magnetic FeCo was coated on SmCo₅ nanochips by the reduction of FeCl₃ and CoCl₂ with hydrazine using ultrasonic waves in the presence of NaOH. The amount of the soft phase coating on the hard magnetic nanochips was controlled by varying the initial ratio of soft-phase precursors to hard magnetic particles during the reaction. The soft-phase coating on the hard phase chips has lead to an enhanced remanence due to an exchange coupling between the soft and the hard magnetic phases at optimal hard/soft phase ratios. The composite chips also show a strong magnetic anisotropy when aligned in a magnetic field. The anisotropic SmCo₅/FeCo core/shell nanocomposite chips are promising candidates as building blocks for high-performance anisotropic nanocomposite bonded or fully dense magnets via a bottom-up fabrication approach.