Kathleen M. McCreary, Adrian G. Swartz, Wei Han, Jaroslav Fabian, Roland K. Kawakami
Many fascinating predictions have been made regarding magnetism in graphene including the formation of magnetic moments from dopants, defects, and edges. While several experimental techniques provide insight into this problem, lack of clear evidence for magnetic moment formation hinders development of this nascent field. Here, we utilize pure spin currents to demonstrate that hydrogen adatoms and lattice vacancies generate magnetic moments in single layer graphene. Pure spin currents are injected into graphene spin valve devices and signatures of magnetic moment formation emerge in the spin transport signal as hydrogen adatoms or lattice vacancies are systematically introduced in an ultrahigh vacuum environment. For this novel method of detecting magnetic moments, the observed behavior is quantitatively explained utilizing a phenomenological theory for scattering of pure spin currents by localized magnetic moments. Furthermore, we observe effective exchange fields due to the spin-spin coupling between conduction electrons and magnetic moments, which are of interest for novel phenomena and spintronic functionality but have not been seen previously in graphene. Thus, the results provide the most clear and direct evidence for magnetic moment formation in graphene and establish a venue for investigating spin-spin exchange coupling in graphene, which are important for future developments in magnetism and spintronics.
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http://arxiv.org/abs/1206.2628
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