Searching for Si-based spintronics by first principles calculations

Hortamani, Mahboubeh; Sandratskii, L. M.; Kratzer, Peter; Mertig, Ingrid

doi:10.1088/1367-2630/11/12/125009

Cited by 16 publications

(12 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the B2-like film, a considerable magnetic moment ͑0.7 B ͒ is also found for the Mn atom in the central layer. Comparing to the ideal cubic B2 bulk structure, which is found to be nonmagnetic in our calculations, 34,35 such an increased magnetic moment may ͑at least partially͒ be attributed to the effect of the tetragonal lattice distortion in the film on the electronic band structure close to the Fermi energy: The vertical distance between layers is about 0.84 Å which is 5% larger than for the B2 bulk phase. Moreover, the magnetic moments of individual atoms are related to their coordination and bond length: The Mn atoms in the surface and interface layer make seven bonds with Si atoms at distances between 2.38 and 2.5 Å, while the Mn atoms in the central layer have eight bonds to Si atoms.…”

Section: B Films With B2-like Structurementioning

confidence: 52%

Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation

2007

Self Cite

View full text Add to dashboard Cite

The stability of thin films and of small crystallites of Mn monosilicide (MnSi) on the Si(111) surface is investigated by density-functional theory calculations. Extending previous studies of MnSi/Si(001), our calculations indicate that MnSi films on Si(111) have similar electronic and magnetic properties, i.e., large magnetic moments at the Mn atoms near the surfaces and interfaces and a high degree of spin polarization at the Fermi level. Hence, such MnSi films could be interesting as a spintronics material compatible with silicon. Moreover, from our calculated total energies we conclude that the Si(111) substrate should be more suitable to grow MnSi layers than the Si(001) substrate. This result is obtained by analyzing the conditions for the formation of three-dimensional (3D) MnSi islands, either in the B20 crystal structure or as pseudomorphic islands in the B2 structure: On Si(001), 3D islands, even if they are just a few lattice constants wide, are found to be already more stable than a homogeneous MnSi film. A bipyramidal “iceberg” island consisting of MnSi in the B20 structure on the Si(001) substrate is found to be most stable among the structures investigated. For MnSi on Si(111), however, our calculations show that the nucleus for forming a 3D island is larger. Therefore, Mn deposition initially leads to the formation of flat 2D islands. On Si(111), the lowest-energy structure for such islands is found to be similar to the B20 structure of bulk MnSi, whereas on Si(001) this structure is incompatible with the substrate lattice. Our results are in agreement with the experimental observations, formation of an almost closed film with (√3x√3) structure on Si(111), and 3D island formation on Si(001)

show abstract

Section: B Films With B2-like Structurementioning

confidence: 52%

Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation

2007

Self Cite

View full text Add to dashboard Cite

show abstract

“…We note that deriving exchange coupling parameters for non-collinear Hamiltonians from collinear ab initio calculations is a known approach that provided a number of significant results for a broad variety of magnetic systems. This includes recent studies of MnSi by Hortamani et al 50 , and Fe 65 Ni 35 by Liot and Abrikosov 51 . Our own work on Fe and Fe/Cr interfaces 45,46 , which followed the same approach, agrees well with experiment and noncollinear ab initio calculations, thus further validating the above approach to the parametrization of Magnetic Cluster Expansion.…”

Section: Magnetic Cluster Expansionmentioning

confidence: 93%

Phase stability of ternary fcc and bcc Fe-Cr-Ni alloys

et al. 2015

View full text Add to dashboard Cite

The phase stability of fcc and bcc magnetic binary Fe-Cr, Fe-Ni and Cr-Ni alloys, and ternary Fe-Cr-Ni alloys is investigated using a combination of Density Functional Theory (DFT), Cluster Expansion (CE) and Magnetic Cluster Expansion (MCE) approaches. Energies, magnetic moments, and volumes of more than 500 alloy structures have been evaluated using DFT, and the predicted most stable configurations are compared with experimental observations. Deviations from the Vegard law in fcc Fe-Cr-Ni alloys, resulting from the non-linear variation of atomic magnetic moments as functions of alloy composition, are observed. Accuracy of the CE model is assessed against the DFT data, where for ternary Fe-Cr-Ni alloys the cross-validation error is found to be less than 12 meV/atom. A set of cluster interaction parameters is defined for each alloy, where it is used for predicting new ordered alloy structures. Fcc Fe2CrNi phase with Cu2NiZn-like crystal structure is predicted to be the global ground state of ternary Fe-Cr-Ni alloys, with the lowest chemical ordering temperature of 650K. DFT-based Monte Carlo (MC) simulations are applied to the investigation of order-disorder transitions in Fe-Cr-Ni alloys. Enthalpies of formation of ternary alloys predicted by MC simulations at 1600K, combined with magnetic correction derived from MCE, are in excellent agreement with experimental values measured at 1565K. The relative stability of fcc and bcc phases is assessed by comparing the free energies of alloy formation. Evaluation of the free energies involved the application of a dedicated algorithm for computing configurational entropies of the alloys. Chemical order is analyzed, as a function of temperature and composition, in terms of the Warren-Cowley Short-Range Order (SRO) parameters and effective chemical pairwise interactions. In addition to compositions close to binary intermetallic phases CrNi2, FeNi, FeNi3 and FeNi8, pronounced chemical order is found in fcc alloys near the centre of the ternary alloy composition triangle. The calculated SRO parameters compare favourably with experimental data on binary and ternary alloys. Finite temperature magnetic properties of fcc Fe-Cr-Ni alloys are investigated using an MCE Hamiltonian parameterized using a DFT database of energies and magnetic moments computed for a large number of alloy configurations. MCE simulations show that the ordered ternary Fe2CrNi alloy phase remains magnetic up to 850-900 K due to strong anti-ferromagnetic coupling between (Fe,Ni) and Cr atoms in the ternary Fe-Cr-Ni matrix.

show abstract

“…The gap at the Fermi level in minority-spin band leads to a large value of the Stoner gap. Half-metallic systems where we have applied our method include the diluted magnetic semiconductors [11], ferromagnetic Heusler alloys like NiMnSb and Co 2 MnSi [22,23,24,25], half-metallic antiferromagnets [26,27], transition metal pnictides and chalcogenides [25,28,29,30], and half-metallic sp-electron ferromagnets [14,31,32]. Moreover these results have served to study several other thermodynamics properties like the temperature dependance of the magnetization in half-metallic antiferromagnets [33] or the thermal properties of the Ni sublattice in NiMnSb [34].…”

Section: Methods and Motivationmentioning

confidence: 99%

Ab-initio calculation of effective exchange interactions, spin waves, and Curie temperature in L21- and L12-type local moment ferromagnets

Galanakis

Şaşıoğlu

2012

J Mater Sci

View full text Add to dashboard Cite

Employing first-principles electronic structure calculations in conjunction with the frozen-magnon method we study the effective exchange interactions and spin waves in local moment ferromagnets. As prototypes we have chosen three L2 1 -type full Heusler alloys Cu 2 MnAl, Ni 2 MnSn and Pd 2 MnSn, and the L1 2 -type XPt 3 compounds with X= V, Cr and Mn. We have also included CoPt 3 which is a usual ferromagnet. In all compounds due to the large spatial separation (∼ 4Å) of the magnetic transition metal atoms, the 3d states belonging to different atoms overlap weakly and as a consequence the exchange coupling is indirect, mediated by the sp electrons. Calculated effective exchange parameters are long range and show RKKY-type oscillations. The spin-wave dispersion curves are in reasonable agreement with available experimental data. Using the calculated exchange parameters we have estimated the Curie temperatures within both the mean-field and the random-phase approximations. In local moment ferromagents deviations of the estimated Curie temperature with respect to the available experimental data occur when the ground-state electronic structure calculations overestimate the values of the spin magnetic moments as in VPt 3 .

show abstract

Searching for Si-based spintronics by first principles calculations

Cited by 16 publications

References 36 publications

Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation

Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation

Phase stability of ternary fcc and bcc Fe-Cr-Ni alloys

Ab-initio calculation of effective exchange interactions, spin waves, and Curie temperature in L21- and L12-type local moment ferromagnets

Contact Info

Product

Resources

About