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Magnetic Properties of Hitperm (Fe,Co)88Zr7B4Cu1 Nanocrystalline Magnets (Invited)

  • M. A. Willard (a1), M. Gingras (a1), M. J. Lee (a1), V. G. Harris (a2), D. E. Laughlin (a1) and M. E. Mchenry (a1)...

Abstract

Alloys consisting of Fe-Co-M-B-Cu (with M = Zr, Hf, Nb), called HITPERM alloys, have been developed. Synchrotron X-radiation studies have been used to show that the ferromagnetic phase in an equiatomic FeCo-based alloy is the α'-FeCo phase. Since both the α'-FeCo phase and the FeCo-based amorphous phase of the nanocrystalline alloy have high Curie temperatures, a high magnetization persists up to the α -> γ structural phase transformation temperature of 980°C. Room temperature AC permeability measurements have shown that the alloys maintain a high permeability of ∼2000 up to a frequency of 20 kHz. The room temperature core loss has also been shown to be competitive with commercial high temperature magnetic alloys with a value of 1 W/g at Bs = 10 kG andf= 10 kHz. Analysis of extended X-ray absorption fine structure (EXAFS) data is consistent with a two-phase mixture of nanocrystalline body centered cubic derivative FeCo structure and an amorphous Zr-rich phase. A differential scanning calorimetry study of the primary crystallization reaction shows an activation energy of 323.3 kJ/mol. As a preliminary study of phase and grain stability, broadening of X-ray diffraction peaks indicates little grain growth after annealing at 600 °C for 3072 hours.

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Magnetic Properties of Hitperm (Fe,Co)88Zr7B4Cu1 Nanocrystalline Magnets (Invited)

  • M. A. Willard (a1), M. Gingras (a1), M. J. Lee (a1), V. G. Harris (a2), D. E. Laughlin (a1) and M. E. Mchenry (a1)...

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