▎ 摘　　要

Investigations of the magnetic properties of graphenes prepared by different methods reveal that dominant ferromagnetic interactions coexist along with anti ferromagnetic interactions in all of the samples, somewhat like in frustrated or phase-separated systems. All of the graphene samples exhibit room-temperature magnetic hysteresis. The magnetic properties of the graphene samples depend on the number of layers and the sample area, small values of both favoring larger magnetization. Molecular charge-transfer affects the magnetic properties of graphene, interaction with a donor molecule such as tetrathiafulvalene having greater effect than with an electron-withdrawing molecule such as tetracyanoethylene.