Influence of spin dynamics of defects on weak localization in paramagnetic two-dimensional metals

Spin-flip scattering of charge carriers in metals with magnetic defects leads to the low-temperature saturation of the decoherence time τφ of electrons at a value comparable to their spin relaxation time τs. In two-dimensional (2D) conductors such a saturation can be lifted by an in-plane magnetic field B, which polarizes spins of scatterers without affecting the orbital motion of free carriers. Here, we show that in 2D conductors with substantially different values of the g factors of electrons (ge) and magnetic defects (gi), the decoherence time τφ(B) (reflected by the curvature of magnetoconductance) displays an anomaly: It first gets shorter, decaying on the scale B∼ /|gi-ge|μBτs, before becoming longer at higher values of B.