Composition-Dependent Assembly and Magnetic Specificity of (Fe1−xNix)0.5Pt0.5 Amorphous Nanothreads Through Substitution of Ni for Fe in an FePt System

A new effective strategy of composition-dependent assembly is first reported to synthesize length-controllable amorphous (Fe 1− x Ni x ) 0.5 Pt 0.5 nanoalloys (nanoparticles, nanorods, and nanothreads) through phase-transfer process. The synthesized nanoalloy morphologies and structures, phase transformation behaviors, and magnetic properties were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), and vibration sample magnetometry (VSM) measurements. The morphologies of as-prepared amorphous nanoalloys show composition-dependent nanothread length variation from 8 μm to 600 nm, which results in different phase-transformation behaviors and magnetic properties. In particular, magnetic specificity is discovered in that the magnetic property of as-obtained amorphous nanoalloys change from soft to hard as Ni content increases, but the variation trend of annealed ones is the inverse case. Thus, a coercivity constant composition point is found at Fe 21 Ni 31 Pt 48 . And FeNiPt nanothreads present larger magnetic anisotropy with higher coercivity of 3kOe than that of its nanoparticles with coercivity of 2.4kOe. In addition, Ni lowers L1 0 kinetic ordering temperature in (Fe 1− x Ni x ) 0.5 Pt 0.5 nanoalloy systems.