DEVELOPMENT OF 3D-PRINTED HALBACH CYLINDER FOR TEACHING AND RESEARCH IN GEOMAGNETISM

Strong magnetic fields are often used to characterize the magnetic mineral assemblage in rocks and sediments. Typically these measurements are only possible in the lab, as the instruments needed to generate large fields are usually large, expensive, water-cooled electromagnets. Here we explore the use of a Halbach array, which is composed of a circular arrangement of carefully positioned magnets that additively create a stronger magnetic field in the center of the circle than that generated by any single magnet in the arrangement. The resulting field in the center of the Halbach array is homogeneous along one axis, while nulled along other axes. Such arrangements have many potential applications due to their portability; yet previous versions of the array have been expensive and/or required substantial resources to build. Here, we explore a more accessible design, constructed using 3D printing to create a rigid frame to position and hold commercially available rare earth magnets. Initially, a small hand-held ring was designed and successfully assembled to accommodate rock chip samples that could be collected in the field. A second, larger outer ring was then designed that can be rotated about the smaller ring to generate a range of adjustable fields. The ability to strongly magnetize a sample while outside in the field using a variety of user-controlled fields has many applications for paleomagnetic and environmental magnetic studies. Most smartphones contain 3-axis magnetometers that can be used to measure a sample’s magnetization after being magnetized by the Halbach array. Thus, we envision that our device could potentially be used in conjunction with a mobile app, allowing field measurements to be taken with a smartphone.