Hysteresis loops of magnetoconductance in graphene devices

We report very low-temperature magnetoconductance G measurements on graphene devices with themagnetic field H applied parallel to the carbon sheet. The G(H) signal depends on the gate voltage Vgand its sign is related to the universal conductance fluctuations. When the magnetic field is swept at fast rates,G displays hysteresis loops evident for different sizes and at different transport regimes of the devices. Weattribute this to the magnetization reversal of paramagnetic centers in the graphene layer, which might originatefrom defects in our devices.