▎ 摘　　要

Flexible magnetic field sensors attract significant interests in magnetic detection and flexible electronics. However, two challenges, low sensitivity, and limited working range, impede their practical application. Herein, a new type of magnetic-sensitive crack sensor (M-CS) by depositing graphene nanosheets upon a flexible magnetic film through a facial infrared drying technique is reported. The M-CS exhibits an ultrahigh sensitivity (relative resistance change up to 4.0 x 10(10)) toward a moderate magnetic field of 43 mT at room temperature. In addition, the M-CS shows a long cycling stability over 10 000 cycles. Such a superior sensitivity is attributed to physically cutting/recovering the pathways of electron transport through nanosheets' separation/contact. Diverse experimental parameters, such as the concentration of graphene solution and the thickness of bottom magnetic substrates, have been tailored to improve the magnetic sensitivity of M-CS. Furthermore, the array of M-CSs with different relative resistance change can be used as the cipher key to recognize aimed magnetic signal without contact. It is believed that the M-CS with an ultrahigh magnetic sensitivity at operational condition and long-term stability could benefit the development of magneto-sensitive sensors, and exploit the application of 2D materials in flexible electronic devices.