Abstract Nanocrystalline Al3+ and Cr3+ doped Ni-Co-Cu ferrites with the chemical composition Ni0.7Co0.2Cu0.1Al0.5xCr0.5xFe2-xO4 (x = 0.0, 0.1, 0.2) were prepared for demonstrating their structural, surface morphological and magnetic characteristics. The technique used for synthesizing the doped and undoped Ni-Co-Cu nanoferrites was sol-gel auto-combustion technique. The existence of single phase was confirmed with the help of X-ray diffractometry (XRD) which indicates the presence of spinel cubic structure for the synthesized specimens. The crystallite size (D) was determined from the highest intense (311) peak of the observed x-ray diffraction patterns by Debye-Scherrer formula and it was found in the dimensions of 44-55 nm. FESEM micrographs shows the existence of agglomerated and spherical magnetic nanoparticles with an average grain size of 63-78 nm. The prepared samples were examined with energy dispersive x-ray spectroscopy for the analysis of purity of synthesized samples and thus, from the EDX spectrum, only peaks of nickel, cobalt, copper, aluminium, chromium, iron and oxygen were observed which confirms the high purity of our results to a next level. The magnetic study was taken into consideration by vibrating sample magnetometer (VSM) and therefore, from the M-H curves data, various magnetic parameters were calculated. From the M-H loops measurements, the maximum of saturation magnetization (Ms) observed was 52.49 emu/g along with few hundreds of coercivity (Hc) indicating the ferromagnetic and soft behaviour of synthesized specimens. Therefore, in the present investigation, excellent values of saturation magnetization (28.11-52.49 emu/g) and coercivity (536.6-591.02 Oe) were obtained making these nanoferrites suitable for the high-density recording media and electromagnets application.

中文翻译：

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用于潜在应用的 Al3+ 和 Cr3+ 取代的 Ni-Co-Cu 纳米铁氧体的结构和磁性研究

摘要 制备了化学成分为 Ni0.7Co0.2Cu0.1Al0.5xCr0.5xFe2-xO4 (x = 0.0, 0.1, 0.2) 的纳米晶 Al3+ 和 Cr3+ 掺杂 Ni-Co-Cu 铁氧体，以证明其结构、表面形态和磁特性. 用于合成掺杂和未掺杂 Ni-Co-Cu 纳米铁氧体的技术是溶胶-凝胶自燃技术。借助 X 射线衍射法 (XRD) 证实了单相的存在，这表明合成样品存在尖晶石立方结构。微晶尺寸 (D) 由观察到的 X 射线衍射图的最高强度 (311) 峰通过 Debye-Scherrer 公式确定，并在 44-55 nm 的尺寸中发现。FESEM 显微照片显示存在平均粒径为 63-78 nm 的团聚球形磁性纳米粒子。制备的样品用能量色散 X 射线光谱分析合成样品的纯度，因此，从 EDX 光谱中，仅观察到镍、钴、铜、铝、铬、铁和氧的峰，这证实了高我们的结果纯度更上一层楼。振动样品磁强计 (VSM) 考虑了磁性研究，因此，根据 MH 曲线数据，计算了各种磁性参数。从 MH 回路测量中，观察到的最大饱和磁化强度 (Ms) 为 52.49 emu/g，以及数百个矫顽力 (Hc)，表明合成样品的铁磁和软行为。所以，