Phase- and Composition-Tunable Hard/Soft Magnetic Nanofibers for High-Performance Permanent Magnet

An exchange-spring magnet is a next-generation permanent magnetic model that possesses a synergistic effect of single-phased hard and soft magnets, thereby giving rise to enhanced magnetic performance. However, in spring magnet preparation thus far, it has remained a challenge to manipulate the magnetic properties via the exchange-coupling effect due to the lack of a synthetic method that enables the hard/soft interfacial magnetic interaction in a homogeneous manner. Here, we report an in situ approach for the synthesis of a phase- and composition-tunable SmCo-based spring magnet based on a binary phase system. This is the first reported systematic and prospective approach to spring magnet preparation. An electrospinning technique with the use of a composition-tunable precursor enables the fabrication of bimagnetic nanofibers with a precisely controlled hard/soft magnet volume ratio 0 to 100%) and a good number of interfacial sites, leading to an effective magnetic coupling interaction. On the basis of a microstructural study and qualitative magnetic measurements, we demonstrate an enhancement in magnetic performance for binary-phased fibers and clearly manifest the elucidation of the exchange-coupling effect between nanograins across the interface in the one-dimensional nanomagnet. We envision that this work can provide a potential approach to develop exchange-coupled spring magnet and moreover, offering an ideal model to understand the nanomagnetism of a well-constructed one-dimensional spring nanostructure.