Strong magnetoresistance in a graphene Corbino disk at low magnetic fields

We have measured magnetoresistance of suspended graphene in the Corbino geometry at magnetic fields up
to B = 0.15 T, i.e., in a regime uninfluenced by Shubnikov—de Haas oscillations. The low-temperature relative
magnetoresistance [R(B) − R(0)]/R(0) is strong, approaching 100% at the highest magnetic field studied, with
a quite weak temperature dependence below 30 K. A decrease in the relative magnetoresistance by a factor of
two is found when charge carrier density is increased to |n| 3 × 1010 cm−2. Furthermore, we find a shift in the
position of the charge neutrality point with increasing magnetic field, which suggests that magnetic field changes
the screening of Coulomb impurities around the Dirac point. The gate dependence of the magnetoresistance
allows us to characterize the role of scattering on long-range (Coulomb impurities, ripples) and short-range
disorder (adatoms, atomic defects), as well as to separate the bulk resistance from the contact one. Based on the
analysis of the magnetoresistance, we propose a more reliable method to extract the bulk mobility, which does
not require prior knowledge of the contact resistance. ... mehrIt is thus demonstrated that studying magnetoresistance in
the Corbino geometry is an extremely valuable tool to characterize high-mobility graphene samples, in particular,
in the vicinity of the Dirac point.