Materials used in spintronics and spin caloritronics, such as thin film ferrimagnetic yttrium iron garnet (YIG), are often grown on bulk substrates, such as gadolinium gallium garnet (GGG), due to their exceptional lattice matching and disordered magnetism.1 Magnetometry measurements can resolve YIG thin films down to a few nanometers, but assuming a linear paramagnetic background when accounting for the GGG substrate can contribute significant artifacts in the resulting signal.2 Superconducting magnet coils are susceptible to trapped flux, leading to measurements performed in the their fields to require precise calibration of the resulting magnetic field, particularly on films with small coercivites or grown on substrates with large paramagnetic susceptibilities. Using a 20nm YIG thin film grown on GGG as an example, we show that performing a simple linear paramagnetic background subtraction can produce artifacts, including negative remanence, vertical exchange bias, and shifts along the field axis. We demonstrate that direct measurements of standalone substrates in carefully reproduced field conditions and field correcting with a standard reference are two ways to minimize the inclusion of these magnetic artifacts in quantitative magnetometry measurements.

References:

1 H. Chang, P. Li, W. Zhang, T. Liu, A. Hoffmann, L. Deng, and M. Wu, Nanometer-thick yttrium iron garnet films with extremely low damping. IEEE Magn. Lett. 5, 1 (2014)
2 Roos, M. J., Quarterman, P., Ding, J., Wu, M., Kirby, B. J., & Zink, B. L.. Magnetization and antiferromagnetic coupling of the interface between a 20 nm Y3Fe5O12film and Gd3Ga5O12 substrate. Physical Review Materials, 6(3), 034401 (2022)