The absence of a Mn local moment was observed in Mn-doped amorphous silicon ͑a-Mn x Si 1−x ͒ films. The magnetic susceptibility obeys the Curie-Weiss law for a wide range of x ͑5 ϫ 10 −3 up to 0.175͒ but with extremely small moment. Magnetization measurements suggest that this behavior occurs because only a small percentage of Mn ͑Mn 2+ states with J = S =5/ 2͒ contribute to the magnetization. Thus, the magnetic moments are quenched for the majority of Mn atoms, contrary to the general belief of the existence of a localized Mn moment in Si. X-ray absorption spectroscopy suggests that the quenching of Mn moments is attributed to the formation of an itinerant but Anderson-localized impurity band, forming at x as low as 5 ϫ 10 −3 .

We investigate proximity-induced superconductivity in monolayers of transition metal dichalcogenides (TMDs) in the presence of an externally generated exchange field. A variety of superconducting order parameters is found to emerge from the interplay of magnetism and superconductivity, covering the entire spectrum of possibilities to be symmetric or antisymmetric with respect to the valley and spin degrees of freedom, as well as even or odd in frequency. More specifically, when a conventional s-wave superconductor with singlet Cooper pairs is tunnel-coupled to the TMD layer, both spin-singlet and triplet pairings between electrons from the same and opposite valleys arise due to the combined effects of intrinsic spin-orbit coupling and a magnetic-substrate-induced exchange field. As a key finding, we reveal the existence of an exotic even-frequency triplet pairing between equal-spin electrons from different valleys, which arises whenever the spin orientations in the two valleys are noncollinear. All types of superconducting order turn out to be highly tunable via straightforward manipulation of the external exchange field.

We investigate pure spin pumping in graphene by imposing a ferromagnet (F) with rotating magnetization on top of it. Using the generalized scattering approach for adiabatic spin pumping, we obtain the spin current pumped through magnetic graphene to a neighboring normal (N) region. The spin current can be easily controlled by gate voltages and under certain conditions, becomes sufficiently large to be measurable in current experimental setups. In fact it reaches a maximum value when one of the spins are completely filtered due to the vanishing density of states of the corresponding spin species in the ferromagnetic part. Considering an N|F|N structure with a finite ferromagnetic region, it is found that in contrast to the metallic ferromagnetic materials the transverse spin coherence length can be comparable to the length of F denoted by L. Subsequently, due to the quantum interferences, the spin current becomes oscillatory function of JL/ vF in which J is the spin splitting inside F. Finally we show, originated from the controllability of pumped spin into two different normal sides, a profound spin battery effect can be seen in the hybrid N|F|N device.