...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Crystallization and magnetic behavior of nanosized nickel ferrite prepared by citrate precursor method
【24h】

Crystallization and magnetic behavior of nanosized nickel ferrite prepared by citrate precursor method

机译：柠檬酸盐前驱体法制备纳米铁氧体的晶化和磁性

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

NiFe_2O_4 nanoparticles have been synthesized by citrate precursor gel formation with subsequent heat treatment. Differential thermal and thermogravimetric (DTA/TG) analyses show that the metal citrates decomposed around 230 °C followed by crystallization of the ferrite. X-ray diffraction (XRD) patterns reveal the formation of the cubic spinel phase in the samples after sintering the gel at 350°C, 500 °C and 700 °C. For the samples annealed at 350 °C and 500 °C a small amount of α-Fe_2O_3 was detected whereas single phase was obtained for the sample annealed at 700 °C. The lattice constant a for all the samples is comparable to the value of the bulk material. The mean crystallite size D_(xrd) of the samples determined from XRD line broadening is 26.2-28.5 nm. Transmission electron microscope (TEM) analysis shows that the single-phase particles form clusters with the particle size in the range of 21-82.5 nm and the most probable value D_(tem) of 55.4 nm. Magnetic measurements show that its Curie temperature T_C is close to the bulk value while the spontaneous magnetization M_s at 5 K is lower than that of the bulk. The thermal variation of M_s in the temperature range from 5 to 300 K can be best fitted to a modified Bloch T~α law with the exponent value a ≈ 2. The magnetization data are explained with reference to the disordered surface spins and the finite size effects. In this investigated temperature range, the coercive force H_C decreases linearly with increasing temperature. The coercivity mechanism in the nanoparticle sample with broad particle size distribution is expected to be complex and different factors which affect the H_c value were proposed.
机译：通过柠檬酸盐前体凝胶形成和随后的热处理合成了NiFe_2O_4纳米颗粒。差示热重和热重分析（DTA / TG）分析表明，金属柠檬酸盐在230°C附近分解，随后铁素体结晶。 X射线衍射（XRD）模式揭示了在350°C，500°C和700°C的温度下烧结凝胶后样品中立方尖晶石相的形成。对于在350°C和500°C退火的样品，检测到少量的α-Fe_2O_3，而在700°C退火的样品获得了单相。所有样品的晶格常数a与散装材料的值相当。由XRD线展宽确定的样品的平均微晶尺寸D_（xrd）为26.2-28.5nm。透射电子显微镜（TEM）分析表明，单相颗粒形成簇，其粒径在21-82.5nm范围内，最可能值D_（tem）为55.4nm。磁测量表明，其居里温度T_C接近整体值，而5 K时的自发磁化M_s低于整体值。 M_s在5到300 K的温度范围内的热变化可以最好地拟合为指数a≈2的修正的Bloch T〜α定律。磁化数据是根据无序表面自旋和有限尺寸来解释的效果。在此研究温度范围内，矫顽力H_C随温度升高而线性降低。预期具有宽粒度分布的纳米颗粒样品中的矫顽力机制很复杂，并提出了影响H_c值的不同因素。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号