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Finemet alloy precipitated phase structure and magnetic properties of first-principles simulations

Author: HuYuPing
Tutor: DangShuE；ZuoZhiJie
School: Taiyuan University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: Finemet Alloy α-Fe phase First-principles Magnetic properties Density of states
CLC: TG132.27
Type: Master's thesis
Year: 2011
Downloads: 26
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Abstract


Soft magnetic properties Finemet alloy is very excellent, its magnetic mechanism is different from the traditional magnetic materials, ongoing exploration of Finemet alloy magnetic mechanism in it's inception. The alloy of Finemet possesses excellent soft magnetic properties is inextricably linked with its microscopic structure. The studies show that the soft magnetic properties of nanocrystalline structure, grain size, α-Fe (Si) component factors FINEMET alloy. Cubic phase geometry of the magnetic properties have a major impact, so research bcc structure of α-Fe (Si) phase magnetic and can Finemet alloy magnetic to reveal Finemet alloy magnetic mechanism has important significance. In this paper, first-principles based on density functional theory calculation the method research Finemet alloys precipitate the crystal structure and magnetic phase α-Fe (Si), and explore the various factors that affect the magnetic properties of the cubic structure of α-Fe (Si) phase. Departure from the electron spin angle, respectively, calculation and analysis of the magnetic properties of the α-Fe (Si) in the different proportions of Si substitution of Fe atoms of different positions in the α-Fe superlattice system. The calculation results show that the spin density of states are the key factors that affect the magnetic properties. Found that Si substitution at the top corners of the α-Fe superlattice Fe atom of the resulting system is better than to replace the system of the Fe atom of the body-centered position magnetic. It can be concluded, within a certain range for the content, as the Si content increases, Si in the α-Fe superlattice increased probability of the apex position, α-Fe (Si) phase of the soft magnetic properties increased, consistent with the experimental results. This research work helps magnetic mechanism understand Finemet alloy. Over the years, people have been trying ratio by alloying elements alloyed or change ingredients to change the soft magnetic properties of the material, in order to investigate the magnetic mechanism. This article calculated by the first-principles simulations based on density functional theory Al different substitution position of the Si dissolved in the different permutation after the α-Fe phase, α-Fe (SiAl) Structure and magnetic phase, so as to explore The impact of of Al partial substitute Nb of Finemet the soft magnetic properties of the alloy. The calculation results show, Al into the crystal phase of the magnetic properties of α-Fe (Si) can be considered from two aspects: First, because of Al and Si s, p orbital hybrid role, led to the d orbitals near the Fermi surface vertical spin increased. Overall up and down spin density of states will increase the magnetic moment of the α-Fe (SiAl) system will increase; second is the Al into the α-Fe (Si) crystalline phase, due to increasing inter-atomic scale differences large, resulting in the amount of the distortion of the lattice is also increased. This will make the bulk density of the crystal grains to increase the grain diameter decreases, the grain diameter is reduced, and a coercive force reduction of the system is advantageous. Although the Al non-magnetic elements, but replaced with Al portion magnetic elements Nb, not only does not cause the magnetic properties decrease, but instead causes the magnetic properties can be improved. Al partial substitution of Nb Finemet alloy soft magnetic influence, mainly by replacing the α-Fe (Si) phase of Fe atoms into the cubic structure of the nano-crystalline phase, through the bcc structure nanocrystalline phase, thus the alloy as a whole magnetic can impact.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Special physical properties of alloys > Special electromagnetic properties of alloy > Special magnetic properties of the alloy
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