标题： 单畴粒子中的去磁效应 显示英文标题

标题： Demagnetisation effects in single-domain particles

摘要： 根据磁学的经典定律，磁性软物体的形状限制了有效磁化率。 例如，球形软磁体的有效磁化率不能超过3。 虽然对于宏观多畴磁性材料来说这是正确的，但我们解释了为什么单畴状态下的磁性纳米颗粒不受此限制。 我们表明，沿主轴的退磁因子之间的差异是相关的，并且可以影响单畴粒子的磁化率，但不像多畴粒子那样限制磁化率。 我们在不同直径（8至150 nm）和不同体积分数（0.1至47 vol%）的球形纳米颗粒上实验验证了这一结果。 与我们的预测一致，我们测量到单畴粒子的磁化率远高于3，实际上高达250以上。 此外，与现有模型相反，我们发现非磁性基质中不相互作用的单畴粒子的磁化率与粒子体积分数成简单的线性关系。 显示英文摘要

摘要： According to the classical laws of magnetism, the shape of magnetically soft objects limits the effective susceptibility. For example, spherical soft magnets cannot display an effective susceptibility larger than 3. Although true for macroscopic multi-domain magnetic materials, we explain why magnetic nanoparticles in a single-domain state do not suffer from this limitation. We show that the differences between demagnetisation factors along principal axes are relevant and can influence susceptibility for single-domain particles, but do not limit the susceptibility as in the case for multi-domain particles. We validate this result experimentally on spherical nanoparticles with varying diameter (8 to 150 nm) and varying volume fraction (0.1 to 47 vol%). In agreement with our predictions, we measure susceptibilities largely above 3, in fact up to more than 250, for single-domain particles. Moreover, contrary to an existing model, we find that the susceptibility of non-interacting single-domain particles in a non-magnetic matrix scales simply linearly with the volume fraction of particles.