# Fileset [R3_Supplimentary information_MDR.pdf](https://mdr.nims.go.jp/filesets/ae864917-d3da-43e9-ae56-7612be0ad057/download) ## Creator Z.H. Li, [H. Suto](https://orcid.org/0000-0003-4387-5862), V. Barwal, [K. Masuda](https://orcid.org/0000-0002-6884-6390), [T.T. Sasaki](https://orcid.org/0000-0002-5952-7638), Z.X. Chen, H. Tajiri, L.S.R. Kumara, T. Koganezawa, K. Amemiya, S. Kokado, [K. Hono](https://orcid.org/0000-0001-7367-0193), [Y. Sakuraba](https://orcid.org/0000-0003-4618-9550) ## Rights [Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International](https://creativecommons.org/licenses/by-nc-nd/4.0/) ## Other metadata [Enhancing atomic ordering, magnetic and transport properties of Mn2VGa Heusler alloy thin films toward negatively spin-polarized charge injection](https://mdr.nims.go.jp/datasets/b7d11426-bb91-499c-830e-1ce1fcd6e5e4) ## Fulltext 1 Supplementary Materials Enhancing atomic ordering, magnetic and transport properties of Mn2VGa Heusler alloy thin films toward negatively spin-polarized charge injection Z.H. Lia, H. Sutoa*, V. Barwala, K. Masudaa, T.T. Sasakia, Z.X. Chena, H. Tajirib, L.S.R. Kumarab, T. Koganezawab, K. Amemiyac, S. Kokadod, K. Honoa, Y. Sakurabaa a National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047, Japan b Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Hyogo, 679-5198, Japan c Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, 305-0801, Japan dGraduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Shizuoka, 432-8561, Japan *Corresponding author: suto.hirofumi@nims.go.jp S.1: Interfacial structure of post-annealed MVG films Fig. S.1. (a) Atomic-resolution HAADF-STEM image, and corresponding (b) EDS elemental maps, and (c) compositional line profiles across the post-annealed MgO/Mn2VGa interface. (d) NBED pattens taken from the Regions A, B, C, and D in (a), respectively. 2 Figure S.1 shows the post-annealed MgO/Mn2VGa interface at 600 °C. The atomic-resolution HAADF-STEM image clearly shows a ~ 1 nm-thick interface (Region B) between the MgO and the Mn2VGa film, Fig. S.1a. The EDS elemental maps and corresponding composition line profiles (Fig. S.1b and 1c) show that the MgO/Mn2VGa interface is enriched in V atoms. Combined with a series of NBED patterns taken from MgO (Region A) to Mn2VGa (Region D), Fig. S.1d, a BCC-structured V phase may be formed at the MgO/Mn2VGa interface with an epitaxial relationship of (001)[110]V // (010)[001]MgO, as previously reported [1,2]. Because pure V is paramagnetic, it has little influence on the magnetic properties of the prepared MVG films. S.2: Composition dependence of anisotropic magnetoresistance measurements Figures S.2a-c shows the AMR ratio as a function of � for Mn2+xV1-xGa (x = −0.2, 0, +0.2) films measured from 10 to 300 K. All MVG films exhibit positive AMR ratios for the current along the [110]MVG, and negative ratios as the current direction aligned with the [100]MVG. The magnitude of negative AMR ratios along the [100]MVG shows a strong composition dependence. The AMR ratio increases with increasing the x and is dramatically enhanced at x = +0.2, which Fig. S.1. The � dependence of the AMR ratio for Mn2+xV1-xGa films with x = (a) −0.2, (b) 0, and (c) +0.2, respectively. Note that the current directions were aligned along [110]MVG and [100] , respectively, and the measurement temperature varied from 10 to 300 K. 3 implies the changes in the electronic band structure with the composition. However, a detailed analysis on the composition dependence of AMR is beyond the scope of this study, and we primarily focus on the stoichiometric sample as discussed in the main text. S.3: Theoretical analysis of anisotropic magnetoresistance results In theoretical calculations of AMR in Mn2VGa (x = 0), we consider that Mn atoms dominate the s–d scattering process because the d-orbital density of states (DOS) of Mn in the spin-down band at the EF is larger than that of V, as shown in Figure S.3. The AMR ratio for the current (I) along the MVG[100] and MVG[110] directions, respectively, is expressed as ���[���] = 2� [���] (S1) where � [���] = ���������,�→�,� � �����,�→�,� ����� ���, →!, − ��, →#, $ − � �%��� ��, →!, & +� �% �� ��,�→#, �� + �(, →!, $) (S2) and ���[���] = 2� [���] (S3) Fig. S.3. d-orbital DOS of L2 -ordered Mn VGa for (a) Mn, and (b) V atoms, respectively. 4 where � [���] = �������*+��,�→,,��-+��,�→�,� . ���*+��,�→,,��-+��,�→�,� ����� ���, →#, − ��, →!, $ − �/%� ��, →#, +�/�0%��1 ��, →!, & + �/%0% �1 ��,�→#, �� + �2 ��, →#, + �2 ��, →!, �3 (S4) The parameters used in these expressions are as follows: λ = 0.0109 eV is the spin–orbit coupling constant for Mn, H = 2 eV is the exchange field estimated from the energy difference in the peak positions between the spin-up and spin-down of the partial Mn d-DOS, and Δ = 0.6 eV is the energy difference in the peak positions between the ε and γ orbitals of the partial Mn d-DOS induced by the crystal field, Fig. S.3a. The other parameters, r, ��,�→#, , ��, →#, , and ��, →!, are defined as � = 4�,�4�,5 = �6�∗65∗ �2 8950�19�0�1:, ��,�→#, = 4�,5→,,�4�,5 = ;� 9,,�0<1950�1 , ��, →#, =4�,�→,,�4�,5 = �; 9,,�0<19�0�1 , ��, →!, = 4�,�→�,�4�,5 = �; 9�,�0<19�0�1 . Here, r is the resistivity ratio of the s–s scattering for the spin-down over the s–s scattering for the spin-up, and ��,=→6, = 4�,>→?,�4�,5 is the resistivity ratio of the s–d scattering from the s state with the σ spin to the m orbital with the spin-down over the s–s scattering for the spin-up. The effective mass of the conduction electrons with the σ spin, @=∗ , is estimated from the calculated energy dispersion diagrams, and its ratio, between the spin-down and the spin-up is estimated as 6�∗65∗ = 1. The amount of partial DOS at the EF for the n state of the m orbital with the σ spin, B6,=0C1, is obtained from the calculated DOS as follows: B�0D1 = 0.00112, B 0D1 = 0.011, B!, 0E1 = 0.259, and B#, 0E1 = 0.372. The uncertainty parameter with the σ spin, ;= , was set as ;� = ; = 0.1 depending on impurities and phonons [3]. Figure S.4a shows the calculated AMR[110] ratio as a function of �B#, 0E1 − B!, 0E1� B!, 0E1F and the contributions from the first (red), second (blue), third (yellow), and fourth (green) terms in 5 (S4). The first term determines the monotonically decreasing trend because ���, →!, −��, →#, $ in the first term is proportional to �B!, 0E1 − B#, 0E1�. In addition, 01 G⁄ 1 in the first term with small Δ means that the first term has the large contribution. Similar to the AMR[110], the first term (red) in AMR[100] also determines the monotonically increasing trend, Fig. S.4b, as ���, →#, − ��, →!, $ in the first term is proportional to �B#, 0E1 − B!, 0E1�, and 01 G⁄ 1 means the large contribution. The �B#, 0E1 − B!, 0E1� B!, 0E1F value is calculated to be 0.435, which results in positive AMR[110] and negative AMR[100] ratios, respectively. References [1] M. Gutsche, H. Kraus, J. Jochum, B. Kemmather, G. Gutekunst, Growth and characterization of epitaxial vanadium films, Thin Solid Films 248 (1994) 18-27. Fig. S.4. The calculated AMR ratio as a function of �B#, 0E1 − B!, 0E1� B!, 0E1F for the current along (a) [110]MVG, and (b) [100]MVG directions, respectively. The contributions from individual terms in Eq. (S2) and Eq. (S4) are also shown. The dashed lines represent the values obtained from the DOS calculation in Fig. S.2. 6 [2] R.W.H. Webster, M.T. Scott, S.R. Popuri, J.W.G. Bos, D.A. MacLaren, Epitaxial vanadium nanolayers to suppress interfacial reactions during deposition of titanium-bearing Heusler alloys on MgO(001), Appl. Surf. Sci. 512 (2020) 145649. [3] S. Kokado, Y. Sakuraba, M. Tsunoda, Spin polarization ratios of resistivity and density of states estimated from anisotropic magnetoresistance ratio for nearly half-metallic ferromagnets, Jpn. J. Appl. Phys. 55 (2016) 108004.