Synthesis Of Soft/hard Magnetic Fept-based Glassy Alloys With Supercooled Liquid Region

摘要

Since the glassy alloys have structural homogeneity on a nanoscopic scale and wide supercooled liquid region, △T_x. (temperature interval between glass transition and crystallization), these materials are recognized as promising microano-materials for nanomachines or micro electro-mechanical systems (MEMS). As one of the microano 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 Fe_(55)Pt_(25)Si_(16)B_2P_2, Fe_(55)Pt_(25)Si_(15)B_3P_2 and (Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(96)Zr_4 (at%) glassy alloys with △T_x of 37 K and 48 K, respectively. With structural change from the glassy phase to a nano-composite structure consisting of Ll_0 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 △T_x followed by annealing for the crystallization of the FePt-based glassy alloys. Considering the high magnetocrystaHine anisotropy of the L1_0 phase, which should lead to room-temperature ferromagnetic stability for component sizes as small as nm-order, these Fe-Pt-based glassy alloys have great potential for fabrication of hard magnetic microano structures.