We present results of magneto-optical investigations of (CoFeB)_x-(Al-O)_100-x film nanocomposites in transverse Kerr effect (TKE) geometry in the spectral range 0.5–4.0 eV and magnetic field up to 3.1 kOe. Nanocomposites were deposited onto a glass-ceramic substrate by ion-beam sputtering. According to the data obtained from resistivity measurements, the percolation threshold is about x_per ≈ 57 at.%, and the critical concentration for metal–insulator transition is about x_c ≈ 48 at.%. The TKE response at room temperature strongly depends on the wavelength of light, applied magnetic field H, and the volume metallic fraction. The TKE field dependence is almost linear to H = 3.1 kOe and identical for 1.57 and 3.06 eV at x ≤ 30 at.%. It means that at x ≤ 30 at.%, nanocomposites consist of only superparamagnetic granules. With increasing concentration x, the TKE field dependence at 3.06 eV becomes more and more similar to the field dependence of ferromagnetic material, but it is not the case at 1.57 eV. For example, the TKE signal for x = 43 at.% measured at 3.06 eV saturates at H = 100 Oe, which indicates the presence of large ferromagnetic regions below x_c. For the same composition, the TKE field dependence measured at 1.57 eV does not saturate and resembles more a superparamagnetic response. The same difference is observed also at x = 49 at.%. The presence of large ferromagnetic regions in completely insulating samples together with separate superparamagnetic granules can be considered as an evidence of superferromagnetic ordering in the vicinity of x_c.

中文翻译：

---

(CoFeB)x-(Al-O)100-x 纳米复合材料的磁光光谱：超铁磁性的证据

我们展示了 (CoFeB) 的磁光研究结果_X-(Al-O) _100-X横向克尔效应 (TKE) 几何形状的薄膜纳米复合材料，光谱范围为 0.5-4.0 eV，磁场高达 3.1 kOe。通过离子束溅射将纳米复合材料沉积到玻璃陶瓷基板上。根据电阻率测量得到的数据，渗透阈值约为X_per ≈ 57 at.%，金属-绝缘体转变的临界浓度约为X_c ≈ 48 原子百分比。室温下的 TKE 响应很大程度上取决于光的波长、外加磁场H，和体积金属分数。TKE 场相关性几乎是线性的H = 3.1 kOe，在 1.57 和 3.06 eV 时相同 X≤ 30 原子百分比。这意味着在X≤ 30 at.%，纳米复合材料仅由超顺磁性颗粒组成。随着浓度的增加X，在 3.06 eV 时的 TKE 场依赖性变得越来越类似于铁磁材料的场依赖性，但在 1.57 eV 时并非如此。例如，TKE 信号为X = 43 at.% 在 3.06 eV 下测量饱和 H = 100 Oe，这表明下方存在大的铁磁区域 X_丙。对于相同的成分，在 1.57 eV 下测量的 TKE 场依赖性不会饱和，更像是超顺磁响应。同样的差异也观察到X= 49 原子百分比。在完全绝缘的样品中存在大的铁磁区域以及单独的超顺磁颗粒可以被认为是在附近的超铁磁排序的证据X_丙。