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Magnetic Determination of Shape Distribution of Single Domain Powders

机译：磁性测定单畴粉末的形状分布

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摘要

By demagnetizing a magnetic powder specimen with diminishing alternating fields of various initial amplitudes and by interpreting the results with the Stoner‐Wohlfarth model, one can obtain information about the shape distribution of the particles. We have done this with powders of acicular γ‐ferric oxide at various temperatures; the temperature variation of the results gives information about the size distribution. The sample is first magnetized to saturation; the diminishing ac field is then applied and the remanence measured. Since the particles are not aligned along the applied field, it is necessary to get the equivalent magnetization curve for an aligned sample by operating on the data mathematically. The results indicate that only a small volume fraction of the γ‐ferric oxide particles are small enough to be a paramagnetic. There is a relatively large volume fraction of particles with nearly zero critical field. We believe this is caused by particles which change their magnetization by a mechanism different from the Stoner‐Wohlfarth uniform rotation. On a volume basis, the shape distribution curves peak at a length‐to‐diameter ratio of about 1.6:1, which gives a coercive force of 300 oersteds. The coercive force agrees very well with measured values. The length‐to‐diameter ratio does not agree with electron microscopic observations, which give a mean of about 5:1.
机译：通过对具有各种初始振幅的交变磁场减小的磁性粉末样品进行消磁，并用Stoner-Wohlfarth模型解释结果，即可获得有关颗粒形状分布的信息。我们已经在不同温度下用针状γ-三氧化二铁粉末进行了处理。结果的温度变化可提供有关尺寸分布的信息。首先将样品磁化至饱和；然后施加一个逐渐减小的交流场并测量剩磁。由于粒子未沿施加的磁场排列，因此有必要通过对数据进行数学运算来获得对齐样本的等效磁化曲线。结果表明，只有一小部分的γ-氧化铁颗粒足够小，可以成为顺磁性。临界体积几乎为零的粒子的体积分数相对较大。我们认为，这是由于粒子通过不同于Stoner-Wohlfarth均匀旋转的机制改变了其磁化强度而引起的。以体积为单位，形状分布曲线以长径比约1.6：1达到峰值，这将产生300奥斯特的矫顽力。矫顽力与测量值非常吻合。长径比与电子显微镜观察结果不一致，电子显微镜观察结果的平均值约为5：1。

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  • 来源
    《Journal of Applied Physics》 |1958年第3期|共2页
  • 作者

    Johnson Clark E.; Brown William Fuller;

  • 作者单位

    Central Research Department, Minnesota Mining and Manufacturing Company, St. Paul 6, Minnesota;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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  • 正文语种 eng
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