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The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

M. Rahmoune
M. Rahmoune
, 
A. Chahed
A. Chahed
, 
A. Amar
A. Amar
, 
H. Rozale
H. Rozale
, 
A. Lakdja
A. Lakdja
, 
O. Benhelal
O. Benhelal
 and 
A. Sayede
A. Sayede
   | Dec 19, 2016
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Published Online: Dec 19, 2016
Page range: 905 - 915
Received: May 24, 2016
Accepted: Oct 19, 2016
DOI: https://doi.org/10.1515/msp-2016-0120
Keywords
© Wroclaw University of Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Total energy as a function of volume per formula unit (f.u.) in the three atomic arrangements: type 1, type 2 and type 3 for the CoMnYZ (Z = Al, Ga, and In) compounds. The curves correspond to the FM state.
Total energy as a function of volume per formula unit (f.u.) in the three atomic arrangements: type 1, type 2 and type 3 for the CoMnYZ (Z = Al, Ga, and In) compounds. The curves correspond to the FM state.

Total energy as a function of volume per formula unit (f.u.) in the three magnetic states FM, AFM and NM for the CoMnYZ (Z = Al, Ga, and In) compounds. The curves correspond to the type 1 structure.
Total energy as a function of volume per formula unit (f.u.) in the three magnetic states FM, AFM and NM for the CoMnYZ (Z = Al, Ga, and In) compounds. The curves correspond to the type 1 structure.

Spin polarized band structure of CoMnYZ (Z = Al, Ga and In) at their equilibrium lattice constant. The red lines correspond to the majority spin bands (minority spin bands).
Spin polarized band structure of CoMnYZ (Z = Al, Ga and In) at their equilibrium lattice constant. The red lines correspond to the majority spin bands (minority spin bands).

Spin-polarized total and partial densities of states (DOS) of CoMnYAl.
Spin-polarized total and partial densities of states (DOS) of CoMnYAl.

Spin-polarized total and partial densities of states (DOS) of CoMnYGa.
Spin-polarized total and partial densities of states (DOS) of CoMnYGa.

Spin-polarized total and partial densities of states (DOS) of CoMnYIn.
Spin-polarized total and partial densities of states (DOS) of CoMnYIn.

Schematic illustration of the origin of the gap in the minority band in CoMnYZ alloy: d1, d2, d3, d4 and d5 denote the dxy, dyx, dzx, dz2, dx2− y2 orbitals, respectively.
Schematic illustration of the origin of the gap in the minority band in CoMnYZ alloy: d1, d2, d3, d4 and d5 denote the dxy, dyx, dzx, dz2, dx2− y2 orbitals, respectively.

Dependence of the HM state on the lattice constant (uniform strain) (a) and at the c/a ratio (tetragonal distortion) (b) of CoMnYZ (Z = Al, Ga, and In). The blue lines correspond to the valence bands maxima and the red lines correspond to the conduction band minima in the minority spin states (spin-down states).
Dependence of the HM state on the lattice constant (uniform strain) (a) and at the c/a ratio (tetragonal distortion) (b) of CoMnYZ (Z = Al, Ga, and In). The blue lines correspond to the valence bands maxima and the red lines correspond to the conduction band minima in the minority spin states (spin-down states).

The variation of the lattice parameter with concentration x of CoMnYGa1−xAlx, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).
The variation of the lattice parameter with concentration x of CoMnYGa1−xAlx, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).

Variation of the band gap Eg and half-metallic gap EHM with concentration x of CoMnYGa1−xAlx, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).
Variation of the band gap Eg and half-metallic gap EHM with concentration x of CoMnYGa1−xAlx, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).

Variation of Curie temperature with concentration x of CoMnYAl1−xGax, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).
Variation of Curie temperature with concentration x of CoMnYAl1−xGax, CoMnYGa1−xInx and CoMnYAl1−xInx Heusler alloys (dotted line is the linear fit).

Semiconducting gap Eg, half-metallic gap EHM, total magnetic moment μtot and Curie temperature Tc of CoMnYAl1−x Inx alloys.

xaEgEHMμtotTc
[Å][eV][eV][μB][K]
06.4120.510.1584482
0.256.46520.436840.09934610
0.56.51610.440.114690
0.756.56410.46850.134738
16.6130.540.1954805

Semiconducting gap Eg, half-metallic gap EHM, total magnetic moment μtot, magnetic moment per atom (Co, Mn, Y, Al, Ga, In), magnetic moment in the interstitial region μint in CoMnYAl, CoMnYGa and CoMnYIn compounds.

CompoundEg [eV]EHM [eV]μtot [μB]μCoμMnμYμXμint
CoMnYAl0.510.15840.8273.5−0.108μ0.08μ0.139
CoMnYGa0.590.29440.83.555μ0.111μ0.072μ0.09
CoMnYIn0.540.19540.753.6μ0.137μ0.058μ0.16

Semiconducting gap Eg, half-metallic gap EHM, total magnetic moment μtot and Curie temperature Tc of CoMnYGa1−x Inx alloys.

xaEgEHMμtotTc
[Å][eV][eV][μB][K]
06.3870.590.2944616
0.256.44030.540.234690
0.56.4970.52310.24757
0.756.55080.5050.184774
16.6130.540.1954805

Calculated total energies Etot per formula unit, equilibrium lattice constant a0, bulk modulus B and formation energy Ef for CoMnYZ (Z = Al, Ga, In) compounds in their different structure types and magnetic configurations.

Compound StructureEtot [Ry]a0 [Å]B0 [GPa]Ef [Ry])
NMFMAFMFMFMFM
CoMnYAlType 1−12361.325192−12361.373842−12361.3536146.412100.212−1.294
Type 2−12361.227488−12361.323233−12361.2808556.45395.178−1.243
Type 3−12361.325135−12361.369712−12361.3427896.422102.798−1.288
CoMnYGaType 1−15763.903474−15763.961374−15763.9255826.38795.621−1.228
Type 2−15763.831806−15763.934409−15763.8546326.43693.368−1.142
Type 3−15763.903455−15763.949612−15763.9255826.38998.016−1.189
CoMnYInType 1−23642.224948−23642.301847−23642.2371736.61392.844−1.168
Type 2−23642.137606−23642.251825−23642.1856876.67283.238−1.101
Type 3−23642.225186−23642.275945−23642.2758696.60994.409−1.148

Semiconducting gap Eg, half-metallic gap EHM, total magnetic moment μtot and Curie temperature Tc of CoMnYGa1−xAlx alloys.

xaEgEHMμtotTc
[Å][eV][eV][μB][K]
06.3870.590.2944616
0.256.39090.48860.1764593
0.56.39650.47630.1574553
0.756.40340.46930.142344514
16.4120.510.1584482
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