A magnetic random access memory (MRAM) physically unclonable function (PUF) device that uses the geometric variations in magnetic memory cells to generate a random PUF response is described herein. Within the MRAM, one or more magnetic memory cells can be used for the PUF. The PUF response is generated by destabilizing the one or more magnetic memory cells and then allowing them to relax. The MRAM PUF has also a relatively small footprint among all other silicon PUFs. Timing and control signals for the MRAM PUF are also described along with power and delay characteristics for use with field and spin transfer torque driven destabilization operations.