Mn₂Mo₃O₈ simultaneously exhibits ferroelectric polarization and unique magnetic properties, such as strong magnetoelectric coupling and magnetic-field-induced collinear-to-noncollinear spin structure transitions. However, practical applications of multiferroic Mn₂Mo₃O₈ are hindered by low spontaneous magnetization (0.01 μ_B/f.u. at 2 K) owing to the collinear spin order. Herein, we report the emergence of large spontaneous magnetization of 0.35 μ_B/f.u. by applying 0.5% tensile strain to c-axis-oriented Mn₂Mo₃O₈ epitaxial films. The Mn and Mo valence states were divalent and tetravalent, respectively. The enhanced spontaneous magnetization was directed in the in-plane direction, in contrast to that in the case of the bulk. These results suggest that the film has a noncollinear spin structure with tilted Mn²⁺ magnetic moments from the c-axis probably due to the tensile strain. We also performed first-principles calculations and demonstrated that the direction of the Mn²⁺ magnetic moment is sensitive to tensile strain.

中文翻译：

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极性 Mn2Mo3O8 中的外延应变诱导自发磁化

Mn ₂ Mo ₃ O ₈同时表现出铁电极化和独特的磁性，如强磁电耦合和磁场诱导的共线到非共线自旋结构转变。然而，由于共线自旋顺序，多铁性 Mn ₂ Mo ₃ O _{8 的}实际应用受到低自发磁化强度（2 K 时为0.01 μ _B /fu）的阻碍。在此，我们报告了通过对c轴取向的 Mn ₂ Mo ₃ O ₈施加 0.5% 的拉伸应变，出现了 0.35 μ _B /fu的大自发磁化强度外延薄膜。Mn 和 Mo 价态分别为二价和四价。增强的自发磁化指向面内方向，与块体的情况相反。这些结果表明，薄膜具有非共线自旋结构，其 Mn ²⁺磁矩从c轴倾斜，可能是由于拉伸应变。我们还进行了第一性原理计算并证明了 Mn ²⁺磁矩的方向对拉伸应变敏感。