Abstract
Knowing the distribution of a magnetic field in bulk materials is important for understanding basic phenomena and developing functional magnetic materials. Microscopic imaging techniques employing X-rays, light, electrons, or scanning probe methods have been used to quantify magnetic fields within planar thin magnetic films in 2D or magnetic vector fields within comparable thin volumes in 3D. Some years ago, neutron imaging has been demonstrated to be a unique tool to detect magnetic fields and magnetic domain structures within bulk materials. Here, we show how arbitrary magnetic vector fields within bulk materials can be visualized and quantified in 3D using a set of nine spin-polarized neutron imaging measurements and a novel tensorial multiplicative algebraic reconstruction technique (TMART). We first verify the method by measuring the known magnetic field of an electric coil and then investigate the unknown trapped magnetic flux within the type-I superconductor lead.
Highlights
Knowing the distribution of a magnetic field in bulk materials is important for understanding basic phenomena and developing functional magnetic materials
The fundamental problem of imaging and measuring magnetic vector fields inside solid matter is the necessity to use a probe that is sensitive to magnetic fields on the one hand, but penetrative enough to reach the region of interest inside a material on the other
Several approaches have been suggested to make use of the potential of spin-polarized neutron imaging for 3D magnetic vector field measurements in bulk materials[20,21,22,23], but quantitative tomography has only been demonstrated for simple, onedimensional magnetic fields, where the field vectors vary only in strength but not in direction[24,25]
Summary
Knowing the distribution of a magnetic field in bulk materials is important for understanding basic phenomena and developing functional magnetic materials. We show how arbitrary magnetic vector fields within bulk materials can be visualized and quantified in 3D using a set of nine spin-polarized neutron imaging measurements and a novel tensorial multiplicative algebraic reconstruction technique (TMART). An approach based on ptychographic X-ray nano-tomography has been demonstrated to provide magnetic contrast[12,13] This technique has been further extended to investigate the magnetic vector field in 3D in a GdCo2 sample[14]. Light and X-rays interact mainly with atomic electron shells and only weakly with a magnetic field directly Due to their spin, electrons are very sensitive to magnetic fields, but they have only limited penetration depths. The data obtained serve as an input for a specially developed reconstruction algorithm used to extract the full three-dimensional magnetic vector field distribution
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