The Co₂MnSi (CMS) Heusler alloy compound with ordered crystalline structure is attractive for a number of applications due to soft ferromagnetic properties, high Curie temperature (T_C ≅ 985 K), high saturation magnetization (M_s ≅ 5.1 µ_B/f.u), and predicted full spin polarization of carriers. In this work, we report preparation and properties of nanocrystalline CMS films with thickness d = 120 nm magnetron sputtered onto Si(100) substrates followed by annealing in vacuum at T_a = 300 ÷ 500 °C. Nanocrystalline structure of partially ordered cubic B2 phase with grain diameter d = 15 ÷ 30 nm increasing gradually with T_a has been indicated after annealing at T_a ≥ 400 °C. The angle-dependent differential susceptibility measurements revealed an interesting evolution of magnetic properties of the films in a course of postdeposition annealing at T_a=500 °C. Formation of isolated FM particles demonstrating the angle-dependent coercivity H_c(α) following the well-known Stoner–Wohlfarth model has been indicated after 0.5 h annealing. However, the Kondorsky low H_c ~ 1/cosα demonstrating a strong pinning of domain walls has been certified for similar films after 1.5 h annealing. At the same time, long-term (~ 5 h) annealing at 500 °C revealed reduced magnetization of the films due to a decomposition of the material. Nevertheless, electrical transport measurements revealed low field magnetoresistance of these films of about 0.1% and 0.05% at 80 and 295 K, respectively, demonstrating tunneling of spin-polarized carriers between nanocrystalline grains.

中文翻译：

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后退火Co 2 MnSi Heusler合金膜的磁和电性能

具有柔和的铁磁特性，居里温度高（T _C  K 985 K），高饱和磁化强度（M _s  µ 5.1 µ _B / fu ）的具有规则晶体结构的Co ₂ MnSi（CMS）Heusler合金化合物在许多应用中具有吸引力。），并预测了载流子的全自旋极化。在这项工作中，我们报告了厚度为d  = 120 nm磁控管溅射到Si（100）衬底上的纳米晶CMS膜的制备和性能，然后在真空中以T _a  = 300÷500°C进行退火。晶粒直径d  = 15÷30 nm的部分有序立方B2相的纳米晶体结构随着Ť_一个已在退火后显示Ť_一个 ≥400℃。取决于角度的微分磁化率测量结果表明，在T _a = 500°C的沉积后退火过程中，薄膜的磁性能发生了有趣的变化。在0.5 h退火后，已表明形成了独立的FM粒子，表明遵循众所周知的Stoner-Wohlfarth模型，其矫顽力H _c（α）与角度有关。然而，Kondorsky低 ħ _Ç  〜1 / COS α在1.5 h退火后，证明了对畴壁的牢固钉扎已被证明可用于类似薄膜。同时，在500°C下长期（〜5 h）退火表明，由于材料的分解，薄膜的磁化强度降低。然而，电传输测量显示这些薄膜在80 K和295 K时的低场磁电阻分别约为0.1％和0.05％，这表明纳米晶晶粒之间自旋极化的载流子隧穿。