Spin relaxation of localized electrons in monolayer MoSe2: Importance of random effective magnetic fields

We study the Hanle and spin polarization recovery effects on resident electrons in a monolayer MoSe2 on EuS. We demonstrate that localized electrons provide the main contribution to the spin dynamics signal at low temperatures below 15 K for small magnetic fields of only a few mT. The spin relaxation of these electrons is determined by random effective magnetic fields due to a contact spin interaction, namely the hyperfine interaction with the nuclei in MoSe2 or the exchange interaction with the magnetic ions of the EuS film. From the magnetic field angular dependence of the spin polarization we evaluate the anisotropy of the intervalley electron g factor and the spin relaxation time. The nonzero in-plane g factor |gx| approximate to 0.1, the value of which is comparable to its dispersion, is attributed to randomly localized electrons in the MoSe2 layer.