Ab initio study on the magneto-structural properties of MnAs

Abstract

The magnetic and structural properties of MnAs are studied with ab initio methods, and by mapping total energies onto a Heisenberg model. The stability of the different phases is found to depend mainly on the volume and on the amount of magnetic order, confirming previous experimental findings and phenomenological models. It is generally found that for large lattice constants the ferromagnetic state is favored, whereas for small lattice constants different antiferromagnetic states can be stabilized. In the ferromagnetic state the structure with minimal energy is always hexagonal, whereas it becomes orthorhombically distorted if there is an antiferromagnetic component in the hexagonal plane. For the paramagnetic state the stable cell is found to be orthorhombic up to a critical lattice constant of about 3.7 Angstrom, above which it remains hexagonal. This leads to the second order structural phase transition between paramagnetic states at about 400 K, where the lattice parameter increases above this critical value with rising temperature due to the thermal expansion. For the paramagnetic state an analytic approximation for the magnitude of the orthorhombic distortion as a function of the lattice constant is given. Within the mean field approximation the dependence of the Curie temperature on the volume and on the orthorhombic distortion is calculated. For orthorhombically distorted cells the Curie temperature is much smaller than for hexagonal cells. This is mainly due to the fact that some of the exchange coupling constants in the hexagonal plane become negative for distorted cells. With these results a description of the susceptibility as function of temperature is given.

References in corpus (6)

• The SIESTA method for ab initio order-N materials simulation
• Efficient index handling of multidimensional periodic boundary conditions
• Ab-initio calculations of exchange interactions, spin-wave stiffness constants, and Curie temperatures of Fe, Co, and Ni
• Can half metallic zincblende MnAs be grown?
• Coordination and chemical effects on the structural, electronic and magnetic properties in Mn pnictides
• Structural transformation induced by magnetic field and colossal magnetoresistance response above 313 K in MnAs

Cited by in corpus (11)

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• Magnetostructure of MnAs on GaAs revisited
• Enhanced electron correlations, local moments, and Curie temperature in strained MnAs nanocrystals embedded in GaAs
• Hyperfine Interactions in MnAs studied by Perturbed Angular Correlations of $\gamma$-Rays using the probe ${}^{77}$Br${\to }^{77}$Se and first principles calculations for MnAs and other Mn pnictides
• Lattice dynamics in the double-helix antiferromagnet FeP
• Basics of the magnetocaloric effect
• Detection of the magneto-structural phase coexistence in MnAs epilayers at a very early stage
• Electronic structure and ferromagnetic behavior in the $M{n}_{1-x}{A}_{x}A{s}_{1-y}{B}_y$ alloys
• Influence of the Fermi surface shape on magnetotransport: the MnAs case