Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Metallographic microstructure and properties of the (metal )

Study on the Magnetic and Structural Properties of Fe-Based and Mn-Based Heusler Alloys

Author CaiYanQiang
Tutor MengFanBin;LuoHongZhi
School Hebei University of Technology
Course Materials Physics and Chemistry
Keywords Heusler alloys Ferromagnetic shape memory alloys Semi-metal Magnetic
Type Master's thesis
Year 2011
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In this paper, we prepared by arc melting method the Ni 50 Fe 25 Ga 25-x the B x (x = 0-4) for a series of samples, and samples of the annealing heat treatment device using XRD, the ac magnetic susceptibility study of the crystal structure of the sample, Curie temperature, and phase transformation behavior. And take advantage of the rapid spinning method were prepared Ni 50 Fe 25 Ga 25-x B x (x = 0 -4) quenching the sample. The study showed that with the increase in B substitution of Ga, and its lattice constant gradually decreases, this is mainly because the atomic radius of the atom B is relatively small, and also found that its Curie temperature is gradually reduced, the phase change temperature increased trend. First-principle calculation using GGA and LDA are two different approximation, the calculated Ni 2 FeZ (Z = B, Al, Ga, In) under three different crystal structure , the energy balance of the relationship of the lattice constant in the ferromagnetic state, the theoretically determined, these materials are the most stable crystal structure and the state diagram of its electronic structure. The calculation results show that the lowest energy corresponding lattice constant with Z atoms from B transform In progressively larger, we believe that the change of the lattice constant from the larger atomic radius, while the face-centered and body-centered structure relative Stability change. The results also show that the Ni 2 FeZ (Z = B, Al, Ga, In) alloy having a strong magnetic, ferromagnetic material. We have successfully synthesized a series of Fe 1.5 of M 0.5 CoSi (M = V, Cr, Mn, Fe) alloy, on theoretical and experimental atom of a number of low-cost electronic doped miscellaneous Fe 2 CoSi electronic structure and magnetic effects work. Theoretical calculations show that the M atom Fe atoms tend to occupy the B bit, rather than the (A, C) bit, and cheap electronic digital doping help near the Fermi level minority spin electronic energy band gap the emergence, the majority spin band electronic state to a higher energy level area, which resulted in the emergence of these alloys in high spin polarization. M atom a substitute for Fe atoms for the decrease of the Curie temperature is not large, the Curie temperature of these alloys were higher than 650K. Calculated spin magnetic moment with the experimental values ??is quite good, replace the reduced number of valence electrons of the atom M Slater - Pauli spin magnetic moments follow curve to reduce. Meanwhile, we respectively GGA and LDA approximate calculation method, respectively, calculated Fe 2 YB (Y = Cr, Mn, Co) alloy in the ferromagnetic state and antiferromagnetic state energy and grain The lattice constant changes in the relationship between the electronic density of states calculate their electron spin polarization, they have a higher rate of spin-polarized discussion the Fe 2 YB (Y = Cr, Mn, Co) alloy each atom of its contribution to the total spin moment.

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