Abstract.

The interaction of two dipolar hard spheres near a surface and under the influence of gravity and external perpendicular magnetic fields is investigated theoretically. The full ground-state phase diagram as a function of gravity and magnetic field strengths is established. A dimer (i.e., two touching beads) can only exist when the gravity and magnetic field strengths are simultaneously not too large. Thereby, upon increasing the magnetic field strength, three dimeric states emerge: a lying state (dimer axis parallel to the substrate), an inclined state (intermediate state between the lying and standing ones) and a standing state (dimer axis normal to the substrate). It is found that the orientation angles of the dimer axis and the dipole moment in the newly discovered inclined phase are related by a strikingly simple Snell-Descartes-like law. We argue that our findings can be experimentally verified in colloidal and granular systems.

Graphical abstract

中文翻译：

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表面的磁性二聚体：重力和外部磁场的影响。

摘要。

理论上研究了表面附近以及在重力和外部垂直磁场的作用下两个偶极硬球的相互作用。建立了完整的基态相图，作为重力和磁场强度的函数。二聚体（即，只有两个碰珠）仅在重力和磁场强度不太大的情况下存在。从而，在增加磁场强度时，出现三种二聚状态：横卧状态（平行于基板的二聚体轴），倾斜状态（横卧和站立状态之间的中间状态）和直立状态（垂直于基板的二聚体轴） ）。发现新发现的倾斜相中的二聚体轴的取向角和偶极矩通过惊人的简单的类似于Snell-Descartes的定律相关。我们认为我们的发现可以在胶体和颗粒系统中进行实验验证。

图形概要