Epitaxial yttrium iron garnet film as an active medium of an even-harmonic magnetic field transducer

Abstract

The use of epitaxial yttrium iron garnet (YIG) films in transducers excited by a magnetic field rotating in the film plane is considered. The circular excitation of the film allows one to keep it in the saturated monodomain state and exclude the Barkhausen noise. Using the ferrodielectric material enables one to avoid eddy-current losses, which limit the excitation frequency—and thus the magnetometer sensitivity—and are also an additional source of noise. Conditions of simultaneous measuring of three orthogonal magnetic field components by the YIG single-crystal film have been established. Theoretical analysis of the intrinsic noises of the magnetic material and coils is performed. The prospective way is described to design the magnetometer with noise of several fT Hz−1/2 at room temperature. The prototype of the 3D magnetometer was experimentally tested, demonstrating the detection level below 1 pT Hz−1/2 at frequencies above 0.1 Hz. It looks feasible to reach with such sensors at room temperature the detection level of cooled SQUIDs.