Tip Interface Exchange-Coupling Based on "Bi-Anisotropic" Nanocomposites with Low Rare-Earth Content.

Specially designed SmCo/Co magnetic nanocomposites have been fabricated by a "bottom up" process. SmCo nanochips were first prepared by solution-phase chemical synthesis combined with reductive annealing and then coated by chemical deposition of Co nanorods. Both the SmCo nanochips and Co nanorods are anisotropic and could be simultaneously aligned under the external magnetic field. Magnetic measurements applied on these "bi-anisotropic" SmCo/Co composites show high magnetic performance with the Co phase content in a wide range from 10 to 80 wt %. For the first time ever, the applicable exchange-coupled nanocomposites with a rare-earth content lower than 7 wt % was realized, which exhibits the coercivity close to 10 kOe and remanence 31% larger than that of single phase SmCo. 3-D micromagnetic simulations were performed to reveal that the reversal mechanism in the Co phase was transferred from the incoherent mode to the coherent mode under a tip interface exchange-coupling with a SmCo surface.