Sensor for a nuclear magnetic resonance apparatus for determining at least one material property of a material sample arranged in a useful volume, comprising: - a magnetic field generating device comprising a planar magnetic arrangement for generating a static magnetic field (130, 135, 136, 137) in the useful volume, wherein the planar magnetic arrangement on a front side facing the useful volume has a plurality of magnetic poles (131, 132, 133, 134) which are arranged next to each other with respectively alternating orientation along a first direction of extent of the planar magnetic arrangement, and - a measuring device for measuring a signal based on nuclear magnetic resonance of the material sample arranged in the useful volume, comprising an electric coil having at least one winding (141, 142, 143, 144) for generating an alternating magnetic field (150, 154, 155) in the useful volume, wherein the winding (141, 142, 143, 144) is arranged between two directly adjacent magnetic poles (131, 132, 133, 134) of the planar magnetic arrangement so that the alternating magnetic field (150, 154, 155) of the electric coil overlaps with the static magnetic field (130, 135, 136, 137) of the planar magnetic arrangement substantially orthogonally in the entire useful volume, wherein the planar magnetic arrangement, along the first direction of extent and along a second direction of extent which runs perpendicular to the first direction of extent, in each case comprises a plurality of magnetic segments (121 i,j) arranged next to each other and each having magnetization directions oriented orthogonal to the second direction of extent of the planar magnetic arrangement, and wherein magnetic segments (121 i,j) which are arranged directly next to each other along the first direction of extent of the planar magnetic arrangement each have magnetization directions which are twisted relative to each other, as a result of which a substantially stronger static magnetic field is generated on the front side of the planar magnetic arrangement than on the back side of the planar magnetic arrangement, wherein the magnetic segments (121 i,j) arranged next to each other along the second direction of extent of the planar magnetic arrangement have the same magnetization direction, wherein the electric coil is designed in the form of a multi-resonant coil. - a magnetic field generating device comprising a planar magnetic arrangement for generating a static magnetic field (130, 135, 136, 137) in the useful volume, wherein the planar magnetic arrangement on a front side facing the useful volume has a plurality of magnetic poles (131, 132, 133, 134) which are arranged next to each other with respectively alternating orientation along a first direction of extent of the planar magnetic arrangement, and - a measuring device for measuring a signal based on nuclear magnetic resonance of the material sample arranged in the useful volume, comprising an electric coil having at least one winding (141, 142, 143, 144) for generating an alternating magnetic field (150, 154, 155) in the useful volume, wherein the winding (141, 142, 143, 144) is arranged between two directly adjacent magnetic poles (131, 132, 133, 134) of the planar magnetic arrangement so that the alternating magnetic field (150, 154, 155) of the electric coil overlaps with the static magnetic field (130, 135, 136, 137) of the planar magnetic arrangement substantially orthogonally in the entire useful volume, wherein the planar magnetic arrangement, along the first direction of extent and along a second direction of extent which runs perpendicular to the first direction of extent, in each case comprises a plurality of magnetic segments (121 i,j) arranged next to each other and each having magnetization directions oriented orthogonal to the second direction of extent of the planar magnetic arrangement, and wherein magnetic segments (121 i,j) which are arranged directly next to each other along the first direction of extent of the planar magnetic arrangement each have magnetization directions which are twisted relative to each other, as a result of which a substantially stronger static magnetic field is generated on the front side of the planar magnetic arrangement than on the back side of the planar magnetic arrangement, wherein the magnetic segments (121 i,j) arranged next to each other along the second direction of extent of the planar magnetic arrangement have the same magnetization direction, wherein the electric coil is designed in the form of a multi-resonant coil.