Strain control of magnetocrystalline anisotropy and energy product of MnGa alloys

Abstract

a b s t r a c tWe investigate the energy product of MnGa alloys as function of Mn concentration and applied elastic strain. Using the density functional theory (DFT) based method we calculated the magnetocrystalline anisotropy (MAE) and magnetization of Mn-Ga alloys as function of composition, e.g. Mn and Ga, and examined their variation under applied strain. Our calculations show that MAE is very large $ 22-27 M erg/cm 3 in all three considered compositions, e.g. MnGa, Mn 3 Ga and Mn 1.66 Ga. We show that MAE is very robust in MnGa system and remains large in wide range of concentrations and strains both compressive and tensile. We find that bi-axial tensile strain increases MAE in Mn 1.66 Ga alloys. Our study shows that the variation of MAE as function of Mn content is related to the change in electronic structure and, specifically, the Fermi level position with electron population variation. We estimated the theoretical limit of the energy product (BH) max of MnGa, Mn 3 Ga and Mn 1.66 Ga alloys as 23.65, 4.06 and 13.64 MGOe, respectively. We find that volume expansion of the MnGa alloys (by appropriate doping) should increase the magnetization and the energy product of these alloys.

Noncollinear Magnetic Modulation of Weyl Nodes in Ferrimagnetic Mn$_3$Ga

“…The calculated lattice parameters a = b=3.78 Å and c=7.08 Å, are in good agreement with previous calculations 33,38,39 , which are, however, lower than the experimental values of a = b=3.92 Å and c=7.08 Å. Our calculated values of the magnetic moments of -2.83 µ B and 2.30 µ B for the Mn I and Mn II atoms, respectively, are in good agreement with previous DFT calculations 33,38,39 . In the presence of SOC, the symmetry conservation depends on the magnetic orientation and the crystalline symmetries.…”

Compositional Dependence of Epitaxial L10‐MnxGa Magnetic Properties as Probed by 57Mn/Fe and 119In/Sn Emission Mössbauer Spectroscopy

“…Although the Sn daughter atoms do not possess intrinsic magnetic moment, the neighboring Mn ions can induce a transferred hyperfine field due to the polarization of nonlocalized s electrons of the 119 Sn nuclei by the d electrons around Mn ions. [33,39,40] Within this assumption, the data reported in Figure 7 can be interpreted by using a distribution of magnetically-split sextets with an average hyperfine field values up to 35 T, which is a very large value as induced by the transfer mechanism from neighboring Mn lattice sites. The isomer shift value has been found to be δ ¼ 1.8 and δ ¼ 1.2 mm s À1 for Mn 0.8 Ga and Mn 1.4 Ga, respectively.…”

“…[11,39] However, in the off-stoichiometric conditions, the Mn atoms reside in 2e Wyckoff position while the exceeded Mn atoms tend to occupy the natural Ga 1a and 1c positions, which increases the AF coupling between neighboring Mn atoms, thus lowering the overall magnetism as the Mn content increases. [39,40] The magnetic moments of Mn atoms which occupy Ga positions are larger than and antiparallel (%3 μ B =Mn) to those Mn in their natural positions (%2.45 μ B =Mn). [4,26,39] Thus, due to the different atomic environments of the Mn I and Mn II positions (see Figure 1a) in Mn x Ga samples, different isomer shift have been used for the two sextets.…”