title: Nanometre-scale probing of spin waves using single-electron spins.
abstract: Pushing the frontiers of condensed-matter magnetism requires the development of tools that provide real-space, few-nanometre-scale probing of correlated-electron magnetic excitations under ambient conditions. Here we present a practical approach to meet this challenge, using magnetometry based on single nitrogen-vacancy centres in diamond. We focus on spin-wave excitations in a ferromagnetic microdisc, and demonstrate local, quantitative and phase-sensitive detection of the spin-wave magnetic field at ∼50 nm from the disc. We map the magnetic-field dependence of spin-wave excitations by detecting the associated local reduction in the disc's longitudinal magnetization. In addition, we characterize the spin-noise spectrum by nitrogen-vacancy spin relaxometry, finding excellent agreement with a general analytical description of the stray fields produced by spin-spin correlations in a 2D magnetic system. These complementary measurement modalities pave the way towards imaging the local excitations of systems such as ferromagnets and antiferromagnets, skyrmions, atomically assembled quantum magnets, and spin ice.
authors.affiliation: Department of Physics, Harvard University, 17 Oxford St., Cambridge, Massachusetts 02138, USA.
authors.forename: Toeno
authors.initials: T
authors.lastname: van der Sar
authors.affiliation: 1] Department of Physics, Harvard University, 17 Oxford St., Cambridge, Massachusetts 02138, USA [2] Harvard-Smithsonian Centre for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138, USA.
authors.forename: Francesco
authors.initials: F
authors.lastname: Casola
authors.affiliation: 1] Department of Physics, Harvard University, 17 Oxford St., Cambridge, Massachusetts 02138, USA [2] Harvard-Smithsonian Centre for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138, USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Walsworth
authors.affiliation: Department of Physics, Harvard University, 17 Oxford St., Cambridge, Massachusetts 02138, USA.
authors.forename: Amir
authors.initials: A
authors.lastname: Yacoby