Synthesis of soft/hard magnetic FePt-based glassy alloys with supercooled liquid region

Since the glassy alloys have structural homogeneity on a nanoscopic scale and wide supercooled liquid region, Δ Tx (temperature interval between glass transition and crystallization), these materials are recognized as promising micro/nano-materials for nanomachines or micro electro-mechanical systems (MEMS). As one of the micro/nano components, the hard magnetic one is immensely desired. We systematically investigated the effect of metalloids composition in Fe-Pt-metalloids alloys on the glass-forming ability, and developed Fe55 Pt25 Si16 B2 P2, Fe55 Pt25 Si15 B3 P2 and (Fe0.55 Pt0.25 Si0.16 B0.02 P0.02) 96 Zr4 (at%) glassy alloys with Δ Tx of 37 K and 48 K, respectively. With structural change from the glassy phase to a nano-composite structure consisting of L 10 FePt phase, the coercivity significantly increases from 15 A/m to 170 kA/m for the former one. There is possibility for making the hard magnetic components by the fabrication in Δ Tx followed by annealing for the crystallization of the FePt-based glassy alloys. Considering the high magnetocrystalline anisotropy of the L 10 phase, which should lead to roomerature ferromagnetic stability for component sizes as small as nm-order, these Fe-Pt-based glassy alloys have great potential for fabrication of hard magnetic micro/nano structures.