Graphene foam is becoming a material of choice for magnetoelectronic devices due to its large, linear and unsaturated room temperature magnetoresistance. However, the magnetoresistance of graphene foam is not as large as that of monolayer graphene. Herein, we describe how magnetoresistance ~ 100% was detected at room temperature under a magnetic field of 5 T that is comparable to the magnetoresistance in monolayer graphene; the highest magnetoresistance of ~158% was detected at 5 K under a magnetic field of 5 T. Unlike monolayer graphene, graphene foam is far more comfortable with producing in gram scale and utilizing in magnetoelectronic devices.

Room temperature positive magnetoresistance (PMR) in graphene is a conventional phenomenon but we observed large negative magnetoresistance (NMR) in graphene foam (GF)/polydimethylsiloxane (GF/PDMS) at room temperature for the first time. The largest NMR ~ 35% was detected at 250 K, while PMR is observed below 200 K. Furthermore, PMR at all temperatures is observed in regular GF specimens, hence, NMR is the result of the infiltration with the electrically insulating polymer. Forward interference and wavefunction shrinkage model has been employed to understand the transport mechanism in GF/PDMS. A critical temperature ~ 224 K for switching between NMR and PMR is observed at the crystallization temperature of PDMS, suggesting a change in polymer chain conformation may be a major reason leading to NMR in GF/PDMS specimens thus role of mechanical properties of PDMS in NMR cannot be ignored and observed locally via specially resolved atomic force microscopy. In addition, storage modulus and heat flow study shows similar transition temperature (~ 200 K) of NMR to PMR and provide an evidence of mechanical stable specimens. As is known, large, tunable, and unsaturated NMR at room temperature is very useful for future facile practical shapeable magnetoelectronic devices.