垂直记录介质中本征开关场分布的确定：$ΔH(M, ΔM)$方法的数值研究
Determination of intrinsic switching field distributions in perpendicular recording media: numerical study of the $ΔH(M, ΔM)$ method
摘要：
我们提出了一个数值研究的$ΔH(M,ΔM)$方法和它的能力，以准确地确定内在的开关场分布在相互作用的颗粒状磁性材料，如垂直记录介质。特别是，我们研究了这种方法是如何失败的大铁磁颗粒间的相互作用，在这一点上，相关的强相关的磁化反转不能正确地表示的平均场近似，$ΔH(M,ΔM)$方法的基础上。在这项研究中，我们使用了一个2维阵列的对称hysterons，有一个内在的开关场分布的标准偏差$σ$和铁磁最近邻相互作用$J$。我们发现的$ΔH(M,ΔM)$方法是非常准确的小$J/σ$值，而大量的错误开发一旦有效的交换领域变得可比$σ$，证实了早期的结果从微磁模拟。我们还证明，这种故障与偏离数据集冗余，这是一个关键属性的平均场近似。因此，$ΔH(M,ΔM)$方法无法以明确定义和可量化的方式进行评估，仅从数据集即可轻松评估。
英文摘要：
We present a numerical study of the $ΔH(M,ΔM)$ method and its ability to accurately determine intrinsic switching field distributions in interacting granular magnetic materials such as perpendicular recording media. In particular, we study how this methodology fails for large ferromagnetic inter-granular interactions, at which point the associated strongly correlated magnetization reversal cannot be properly represented by the mean-field approximation, upon which the $ΔH(M,ΔM)$ method is based. In this study, we use a 2-dimensional array of symmetric hysterons that have an intrinsic switching field distribution of standard deviation $σ$ and ferromagnetic nearest-neighbor interactions $J$. We find the $ΔH(M,ΔM)$ method to be very accurate for small $J/σ$ values, while substantial errors develop once the effective exchange field becomes comparable with $σ$, corroborating earlier results from micromagnetic simulations. We furthermore demonstrate that this failure is correlated with deviations from data set redundancy, which is a key property of the mean-field approximation. Thus, the $ΔH(M,ΔM)$ method fails in a well defined and quantifiable manner that can be easily assessed from the data sets alone.
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