Monolithic integration of 2D spin valve magnetic field sensors for angular sensing

The determination of the local field direction enables, for instance, migratory birds to find their annual routes from one continent to another, or magnetotactic bacteria to move towards soil rich in nutrients. In analogy, for microelectromechanical systems (MEMS), the ability of detecting the local direction of a magnetic field as a 2D or 3D vector can allow, in principle, a reliable autonomous navigation through environments with a complex or unknown topology. These applications demand, however, a very low power consumption, miniaturizability and fast response times in the milliseconds range. In the following, we present novel 2D sensors based on exchange-biased IrMn / CoFe / Cu / CoFe - NiFe spin valves fulfilling all these requirements. In addition, we test different sensor arrangements. The spatial sensitivity of the constituent single GMR meanders is defined by means of microscopic laser heating and subsequent in-field cooling. By this, a relative pairwise geometric alignment of 90 degrees or 180 degrees, respectively, is achieved for the individual antiferromagnetic pinning layers, providing a maximum signal response for each sensor layout. On the basis of fabricated prototypes with a size of < 0.5 mm(2), we demonstrate that these sensors can readily be employed to detect small magnetic fields as a 2D vector with a high temporal resolution of 100 mu s. (C) 2015 Elsevier Ltd. All rights reserved.