Thin films with stable half-metallic (HM) character and 100% spin-polarization (SP) are required to be used in spintronic devices. The HM character has been predicted theoretically in many Heusler alloys thin films and confirmed by experiments. Full-Heusler alloy Ti2FeSn has been studied extensively. It has been reported that their (001)-oriented thin films with TiFe or TiSn terminations preserve 100% SP, but the HM character is unstable because the edge of the bandgap is closed to the Fermi level EF. Therefore, we investigate the effects of the Co-doping on the structural, electronic and magnetic properties of the bulk full-Heusler alloys Ti2Fe1‒xCoxSn (x=0.00, 0.25, 0.50, 0.75 or 1.00) and their (001)-oriented thin films. The bulk Ti2Fe1‒xCoxSn (x=0.00, 0.25, 0.50, 0.75 or 1.00) alloys are all HM ferromagnets. We investigate twelve possible terminations and show that five of them preserve HM character with 100% SP at the Fermi level EF, while in the remaining seven, surface states emerge in the spin-down channel at the Fermi level EF, significantly reducing their SP. The Co-doping significantly increases the stability of the TiSn slab, also increases its spin-down bandgap E_g^↓ and HM gap E_g^HM at x=0.50. The stable HM character makes it is a slab of maximum benefit in the applications of spintronic devices, especially in magnetic tunnel junctions.

中文翻译：

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Co掺杂全Heusler合金Ti2Fe1−xCoxSn（x=0.00、0.25、0.50、0.75或1.00）的（001）取向薄膜中稳定的半金属性


自旋电子器件需要具有稳定的半金属 (HM) 特性和 100% 自旋极化 (SP) 的薄膜。许多霍斯勒合金薄膜的 HM 特性已在理论上得到预测，并通过实验得到证实。全霍斯勒合金 Ti2FeSn 已被广泛研究。据报道，他们的具有 TiFe 或 TiSn 终端的 (001) 取向薄膜保留了 100% SP，但 HM 特性不稳定，因为带隙边缘接近费米能级 EF。因此，我们研究了Co掺杂对大块全Heusler合金Ti2Fe1−xCoxSn（x=0.00、0.25、0.50、0.75或1.00）及其（001）取向薄层的结构、电子和磁性能的影响。电影。大块 Ti2Fe1−xCoxSn (x=0.00、0.25、0.50、0.75 或 1.00) 合金都是高模铁磁体。我们研究了 12 种可能的终止，结果表明其中 5 种保留了 HM 特征，在费米能级 EF 处具有 100% SP，而在其余 7 种中，表面态出现在费米能级 EF 处的自旋向下通道中，显着降低了它们的 SP。共掺杂显着提高了 TiSn 板的稳定性，还增加了 x=0.50 时的自旋向下带隙 E_g^↓ 和 HM 带隙 E_g^HM。稳定的 HM 特性使其成为自旋电子器件应用中具有最大优势的板，特别是在磁隧道结中。