The present disclosure relates to a magnetic sensor that comprises a magnetic-sensing element and a magnetic-affecting element. The magnetic sensor is configured for detecting one or more properties, and/or changes therein, of a target magnetic-field. Further embodiments of the present disclosure relate to a sensor unit that houses and protects the magnetic sensor described herein. Further embodiments of the present disclosure relate to a system that comprises the magnetic sensor alone or the sensor unit described herein. Further embodiments of the present disclosure relate to a method for detecting changes in a target magnetic-field. The magnetic sensor described herein comprises a magnetic-sensing element and a magnetic-affecting element. The magnetic-affecting element attracts or attracts and focuses the target magnetic-field through the magnetic-sensing element.