In magnetic systems with reduced dimensionality, the effects of dipolar interactions allow the existence of long-range ordered phases. Long-range magnetic-dipolar interactions are at the heart of the explanation of many peculiar phenomena observed in nuclear magnetic resonance, ferromagnetic resonance, and Bose-Einstein-condensate structures. In this paper we show that magnetic-dipolar-modes (MDMs) in quasi-2D ferrite disks are characterized by symmetry breaking effects. Our analysis is based on postulates about a physical meaning of the magnetostatic-potential function as a complex scalar wave function, which presumes the long-range phase correlations. An important feature of the MDM oscillations in a ferrite disk concerns the fact that a structure with symmetric parameters and symmetric basic equations goes into eigenstates that are not space-time symmetric. The proper solutions are found based on an analysis of magnetostatic-wave propagation in a helical coordinate system. For a ferrite disk, we show that while a composition of two helical waves may acquire a geometrical phase over-running of during a period, every separate helical wave has a dynamical phase over-running of and so behaves as a double-valued function. We demonstrate that unique topological structures of the fields in a ferrite disk are intimately related to the symmetry breaking properties of MDM oscillations. The solutions give the MDM power-flow-density vortices with cores at the disk center and azimuthally running waves of magnetization. One can expect that the proposed models of long-range ordered phases and space-time violation properties of magnetic-dipolar interactions can be used in other magnetic structures, different from the ferromagnetic-resonance system with reduced dimensionality.
The near fields originated from a small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillations are the fields with broken dual (electric-magnetic) symmetry. Numerical studies show that such fields, called the magnetoelectric (ME) fields, are distinguished by the power-flow vortices and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. These numerical studies can well explain recent experimental results with MDM ferrite disks. In the present paper, we obtain analytically topological characteristics of the ME-field modes. …
Nanoscale Dipolar Fields in Artificial Spin Ice Probed by Scanning NV Magnetometry
RPTU University Kaiserslautern-Landau, Department of Physics and State Research Center OPTIMAS(凯泽斯劳滕-兰道工业大学物理系及OPTIMAS州立研究中心);Thomas J. Watson College of Engineering and Applied Science, Binghamton University(宾汉姆顿大学托马斯·J·沃森工程与应用科学学院);Department of Physics & Astronomy, University of Delaware(特拉华大学物理与天文学系)