Magnetoresistance Measurements as an Alternative to Magnetic Resonance Methods for Studying Paramagnetic Defects*

Magnetic resonance methods such as electronic paramagnetic resonance and other companion methods like electrically detected magnetic resonance have been popular for studying unpaired spins in a wide array of materials. In some situations resonance methods are not feasible — for instance when a system of interest is beneath conductive layers as in three-dimensional integrated circuits.

Recently an alternative approach to probing paramagnetic spins was devised which does not require any electromagnetic resonant field but instead magnetoresistance is measured near zero field [1]. The magnetoresistance arises from correlations between spin pairs that involve either a carrier recombining at a trap or hopping through a trap [2]. This magnetoresistance method can be used in electronic devices to great advantage by probing paramagnetic defect environments such as hyperfine and spin-orbit couplings. A theoretical description of the magnetoresistance effect utilizes a multi-spin stochastic Liouville equation [3] which provides agreement with recombination currents in MOSFETs. For high-nuclear spin defects, the theory predicts new resonances in the magnetoresistance that provide precise determination of hyperfine constants. These results offer a new means of analysis which does not rely on a resonator and are potentially applicable to systems inaccessible to conventional resonance methods.

This work was done in collaboration with the groups of M. E. Flatté (U of Iowa ) and P. A. Lenahan (Penn. State U).

[1] J. Ashton et al, IEEE Trans. on Nucl. Sci. 66, 428 (2019)
[2] J. Rybicki et al, Phys. Rev. Lett. 109, 076603 (2012)
[3] Y. Wang et al, Phys. Rev. X 6, 011011 (2016)