Thermodynamics and Magnetism of YCo5 Compound Doped with Fe and Ni: An Ab Initio Study

Abstract

YCo5 permanent magnet exhibits high uniaxial magnetocrystalline anisotropy energy and has a high Curie temperature. These are good properties for a permanent magnet, but YCo5 has a low energy product, which is notably insufficient for a permanent magnet. In order to improve the energy product in YCo5, we suggest replacing cobalt with iron, which has a much bigger magnetic moment. With a combination of density-functional-theory calculations and thermodynamic CALculation of PHAse Diagrams (CALPHAD) modeling, we show that a new magnet, YFe3(Ni1-xCox)2, is thermodynamically stable and exhibits an improved energy product without significant detrimental effects on the magnetocrystalline anisotropy energy or the Curie temperature.

First-principles Calculation of Magnetocrystalline Anisotropy of Y(Co,Fe,Ni,Cu)$_5$ Based on Full-potential KKR Green's Function Method

“…From the GGA calculations, the uniaxial anisotropy of YFe 3 Co 2 is weaker than that of YCo 5 . The lower value of anisotropy in YFe 3 Co 2 is also confirmed by earlier theoretical calculations using GGA [28].…”

“…As originally mentioned in Ref. [28], if the 1-5 phase can exist stably, YFe 3 (Co 1−x Ni x ) 2 can be a useful magnet with better performance than YCo 5 .…”

“…Additionally, Landa et al concluded that nickel stabilized YFe 3 (Co 1−z Ni z ) 2 from the calculation of phase diagrams (CALPHAD) [28]. According to this result, higher nickel content enhances the stabilization of the 1-5 phases.…”

“…In the past decades, the anisotropy and magnetic properties of pristine YCo 5 have been theoretically calculated [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Some researchers replaced a fraction of cobalt with iron and/or copper to enhance the axial anisotropy of YCo 5 , [18][19][20][21][22][23][24], and others investigated the magnetic properties of YCo 5−x Ni x [22,[25][26][27][28]. Landa et al presented that proposed YFe 3 (Co 1−z Ni z ) 2 has higher energy products than YCo 5 , where iron increases the magnetization and nickel thermodynamically stabilizes the 1-5 phases [28].…”

“…Some researchers replaced a fraction of cobalt with iron and/or copper to enhance the axial anisotropy of YCo 5 , [18][19][20][21][22][23][24], and others investigated the magnetic properties of YCo 5−x Ni x [22,[25][26][27][28]. Landa et al presented that proposed YFe 3 (Co 1−z Ni z ) 2 has higher energy products than YCo 5 , where iron increases the magnetization and nickel thermodynamically stabilizes the 1-5 phases [28]. Many theoretical calculations for both pristine and doped YCo 5 are available; however, there are few systematic studies within a consistent framework.…”