颗粒状 CrO₂ 中的输运加权矫顽力：磁电阻与磁化强度为何不一致
Transport-Weighted Coercivity in Granular CrO2: Why Magnetoresistance and Magnetization Can Disagree
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中文总结 AI 辅助
研究颗粒状 CrO₂ 中磁电阻与磁化强度不一致问题，通过重新分析数据发现电阻最大值处场 Hp 与体矫顽场 Hc 关系受温度和电流影响，利用科恩定理引出输运加权矫顽力概念，指出其可用于相关诊断。
中文摘要 AI 辅助
磁电阻滞后现象常被用于估算磁性材料的矫顽场。我们重新分析了已发表的关于半金属铁磁体 CrO₂ 压实粉末的磁输运和磁测量数据，发现这种识别在颗粒状导体中可能失效。电阻最大值处的场 Hp 可能接近、高于或低于体矫顽场 Hc，这取决于温度和测量电流。对于三个具有不同颗粒形状和绝缘壳厚度 的样品，数字化比率 Hp/Hc 遵循相同的定性序列，并表明在 15 K 附近存在一个共同的交叉点。我们将这种行为解释为颗粒间结控制电响应的变化。体磁测量对整个磁体体积进行平均，而隧穿电阻对承载电流的一小部分链路赋予最大权重。科恩的精确网络灵敏度定理提供了这些输运权重的严格线性响应定义。简单来说，科恩表明给定接触对总电阻的影响与流过该接触的电流平方成正比。结合已知的磁对关联效应，这就引出了输运加权矫顽力的概念。在颗粒状传感器和自旋相关复合材料中，电阻峰值不能自动被视为体矫顽场。相反，Hp - Hc 的差值可用于诊断电流路径定位、势垒演化和器件间的变异性。
英文摘要
Magnetoresistance hysteresis is often used to estimate the coercive field of a magnetic material. We reanalyse our published magnetotransport and magnetometry data on compacted powders of the half-metallic ferromagnet CrO2 and show that this identification can fail in a granular conductor. The field Hp at the resistance maximum may be close to, above, or below the bulk coercive field Hc, depending on temperature and measuring current. For three samples with different particle shapes and insulating-shell thicknesses, the digitized ratio Hp/Hc follows the same qualitative sequence and suggests a common crossover near 15 K. We interpret this behaviour as a change in which interparticle junctions control the electrical response. Bulk magnetometry averages over the entire magnetic volume, whereas tunnelling resistance gives the largest weight to the small set of links that carries the current. Cohn's exact network-sensitivity theorem provides a rigorous linear-response definition of these transport weights. In simple terms, Cohn showed that the influence of a given contact on the total resistance is proportional to the square of the current flowing through that contact. Combined with known magnetic pair-correlation effects, this leads to the concept of transport-weighted coercivity. In granular sensors and spin-dependent composites, the resistance peak cannot automatically be treated as the bulk coercive field. Conversely, the difference Hp - Hc may serve as a diagnostic of current-path localization, barrier evolution, and device-to-device variability.
