An ultrasensitive room temperature magnetoelectric thin film magnetometer is fabricated on a cantilever beam and includes an active magnetoelectric multilayer structure having a plurality of thin films formed at a region defined on the cantilever beam. Upon application of a magnetic field, the active magnetoelectric structure generates a corresponding response of an electrical nature which is a measure of a value of the applied magnetic field. The material of the cantilever beam may be removed beneath the active magnetoelectric multilayer structure to form a freestanding modification of the magnetometer with superior sensitivity. The active magnetoelectric multilayer structure is either a bi-layer structure which includes a piezoactive (piezoelectric and/or piezoresistive) thin film deposited in contact with a magnetostrictive thin film or a tri-layer active structure (in the free-standing implementation) including a piezoactive thin film sandwiched between a pair of magnetostrictive thin films.