Experimental Realization of a Magnetic Cloak

Abstract

Invisibility to electromagnetic fields has become an exciting theoretical possibility. However, the experimental realization of electromagnetic cloaks has only been achieved starting from simplified approaches (for instance, based on ray approximation, canceling only some terms of the scattering fields, or hiding a bulge in a plane instead of an object in free space). Here, we demonstrate, directly from Maxwell equations, that a specially designed cylindrical superconductor-ferromagnetic bilayer can exactly cloak uniform static magnetic fields, and we experimentally confirmed this effect in an actual setup.

Manipulating DC Currents with Bilayer Bulk Natural Materials

“…Recently, many significant achievements have been made in the manipulation of magnetostatic field [10][11][12][13][14][15] , thermal conduction [16][17][18][19] , and electrostatic field [20][21][22][23][24] . In 2007, Wood and Pendry proposed a dc metamaterial that pointed the way towards the design of static magnetic cloak [10] , and the dc metamaterial was experimentally verified soon afterwards [11] .…”

“…In 2007, Wood and Pendry proposed a dc metamaterial that pointed the way towards the design of static magnetic cloak [10] , and the dc metamaterial was experimentally verified soon afterwards [11] . Recently, the dc magnetic cloak is theoretically investigated [12] and experimentally realized using superconductors and ferromagnetic materials [13,14] . By using the same materials as dc magnetic cloak, the theoretical realization of a dc magnetic concentrator is also demonstrated [15] .…”

“…Besides making objects invisible [1][2][3][4] , many other novel devices are rapidly emerging, with a representative one being a concentrator [5,6] that can enhance the energy density of incident waves in a given area. In addition to manipulation of EM waves [1][2][3][4][5][6] , the theoretical tool of coordinate transformation has been extended to other areas of physics (such as acoustic waves [7] , matter waves [8] and elastic waves [9] ).Recently, many significant achievements have been made in the manipulation of magnetostatic field [10][11][12][13][14][15] , thermal conduction [16][17][18][19] , and electrostatic field [20][21][22][23][24] . In 2007, Wood and Pendry proposed a dc metamaterial that pointed the way towards the design of static magnetic cloak [10] , and the dc metamaterial was experimentally verified soon afterwards [11] .…”

“…Also, the proposed schemes, derived directly from the electric conduction equation, are exact rather than approximate ones. Finally, excellent performance can be achieved by employing only natural bulk materials, thus indicating that our advanced scheme may be readily extended for various applications beyond dc control [7,13,14,18,27,28] . show the simulated results of the object with only a single layer of air and copper, respectively; significant distortions can be clearly observed.…”

Transformation Inside a Null-Space Region and a Dc Magnetic Funnel for Achieving an Enhanced Magnetic Flux With a Large Gradient

“…In recent years, many novel devices for DC magnetic fields have been designed or even verified experimentally, including cloaking for DC magnetic fields [9,10], DC magnetic concentrators [11][12][13][14], DC magnetic lenses [15] and DC magnetic hoses [16] by using a new theory called transformation optics (TO) [17,18]. These novel DC magnetic devices can perform excellently in some special applications.…”