title: Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells.
abstract: Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio. When the applied field is non-uniform, as for dipolar magnetic field sources, field gradient is increased as well. A proof-of-concept experimental realization confirms the theoretical predictions. The metamaterial shell is also shown to concentrate time-dependent magnetic fields upto frequencies of 100 kHz.
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Navau
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Mach-Batlle
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Parra
authors.affiliation: Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria.|Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria.
authors.forename: Jordi
authors.initials: J
authors.lastname: Prat-Camps
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Sergi
authors.initials: S
authors.lastname: Laut
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Del-Valle
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Sanchez