Random-phase approximation for critical temperatures of collinear magnets with multiple sublattices:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Gd</mml:mi><mml:mi>X</mml:mi></mml:mrow></mml:math>compounds<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>X</mml:mi><mml:mo>=</mml:mo><mml:mi mathvariant="normal">Mg</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">Rh</mml:mi><m

We study the exchange interactions in half-metallic Heusler alloys using first-principles calculations in conjunction with the frozen-magnon approximation. The Curie temperature is estimated within both mean-field (MF) and random-phase-approximation (RPA) approaches. For the halfHeusler alloys NiMnSb and CoMnSb the dominant interaction is between the nearest Mn atoms. In this case the MF and RPA estimations differ strongly. The RPA approach provides better agreement with experiment. The exchange interactions are more complex in the case of full-Heusler alloys Co2MnSi and Co2CrAl where the dominant effects are the inter-sublattice interactions between the Mn(Cr) and Co atoms and between Co atoms at different sublattices. For these compounds we find that both MF and RPA give very close values of the Curie temperature slightly underestimating experimental quantities. We study the influence of the lattice compression on the magnetic properties. The temperature dependence of the magnetization is calculated using the RPA method within both quantum mechanical and classical approaches.

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“…The temperature dependence of the magnetization can be calculated using a semiclassical analog of Eq. (A12) given by 45,52 …”

Section: Discussionmentioning

confidence: 99%

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

et al. 2005

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“…9 60,61 We note that for the present systems the T C is estimated within the simple meanfield approach, in which the spin fluctuations are neglected. More rigorous treatments like the random phase approximation or classical Monte Carlo methods are expected to reduce mean-field T C by about 40% 52,62,63 especially for the case of Cr 2 Se due to the small number of nearest-neighborhood Cr atoms compared to the Cr 3 Se case, but in both cases T C will stay far above room temperature.…”

Section: Exchange Constants and T Cmentioning

confidence: 99%

Half-metallic antiferromagnetism in Cr2+xSe (0≤x≤
Galanakis
¹
,
Özdoğan
²
,
Şaşıoğlu
³

2012
Phys. Rev. B
22
1
10
0
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We study the behavior of the Cr 2+x Se alloys based on state-of-the-art first-principles electronic structure calculations. We show that these alloys are of special interest since they combine possible applications in spintronics devices with a series of diverse magnetic phenomena. First, we show that Cr 2 Se prefers the C1 b structure while Cr 3 Se crystallizes in the D0 3 lattice. Our calculations suggest that as we dope Cr 2 Se with Cr atoms and move towards Cr 3 Se, all alloys are half-metallic fully compensated ferrimagnets (also known as half-metallic antiferromagnets) with a gap in the spin-down band. All alloys follow a generalized version of the Slater-Pauling rule for the Heusler compounds and we show that for Cr 3 Se a small deviation occurs due to the antibonding single band created by the 4s states of the Cr and Se atoms in the spin-down band structure which crosses the Fermi level. In the case of Cr 3 Se we observe a metamagnetic behavior under hydrostatic pressure since Cr atoms with different symmetry present both itinerant and localized magnetic properties. Finally, calculations based on the frozen-magnon approximation reveal that the strong intersublattice antiferromagnetic coupling between the nearest-neighboring Cr atoms stabilizes the ferrimagnetic character of both Cr 2 Se and Cr 3 Se and leads to estimated Curie temperature exceeding considerably the room temperature. Combination of this feature together with the half-metallic antiferromagnetism makes the Cr 2+x Se alloys ideal for realistic spintronics applications.

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“…The obtained exchange interactions were used to construct the classical Heisenberg model, from which we evaluated the critical temperature. Two approximations were used -the mean field approximation (MFA) and multi-sublattice random phase approximation (RPA) [13].…”

Section: Methodsmentioning

confidence: 99%

Magnetic Exchange Interactions and Estimation of T_Nin CsNiF₃from First Principles

Legut

Rusz

2008

Acta Phys. Pol. A

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The CsNiF 3 has been for long time studied as a prototype of quasi-1D planar ferromagnetic system. At very low temperature the studied system is insulator and therefore the magnetic exchange interactions should decay very rapidly. We treated the magnetic exchange coupling within the Heisenberg model for the nearest neighbor interaction between the antiferromagnetically coupled Ni-chains. The influence of up to the second--nearest neighbors on the ferromagnetic exchange coupling along the Ni-chains was determined. The exchange interactions were calculated for the experimental volume by the density functional theory, within the all-electron approach using the local density approximation for the exchange and correlation. The Néel temperature was calculated by means of the mean-field theory and by the random-phase approximation method.

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Random-phase approximation for critical temperatures of collinear magnets with multiple sublattices:GdXcompounds(X=Mg,Rh

Cited by 85 publications

References 29 publications

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

Half-metallic antiferromagnetism in Cr2+xSe (0≤x≤
Galanakis
¹
,
Özdoğan
²
,
Şaşıoğlu
³

2012
Phys. Rev. B
22
1
10
0
View full text Add to dashboard Cite

Magnetic Exchange Interactions and Estimation of T_Nin CsNiF₃from First Principles

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Random-phase approximation for critical temperatures of collinear magnets with multiple sublattices:GdXcompounds(X=Mg,Rh

Cited by 85 publications

References 29 publications

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

Half-metallic antiferromagnetism in Cr2+xSe (0≤x≤Galanakis1, Özdoğan2, Şaşıoğlu3 2012Phys. Rev. B221100View full textAdd to dashboardCite

Magnetic Exchange Interactions and Estimation of TNin CsNiF3from First Principles

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Half-metallic antiferromagnetism in Cr2+xSe (0≤x≤
Galanakis
¹
,
Özdoğan
²
,
Şaşıoğlu
³

2012
Phys. Rev. B
22
1
10
0
View full text Add to dashboard Cite

Magnetic Exchange Interactions and Estimation of T_Nin CsNiF₃from First Principles