On the role of hydrogen in organic magnetoresistance: A study of C60 devices

The organic magnetoresistive (OMAR) effect has been observed in many different organic semiconductors, whereas a corresponding effect has not been reported for inorganic ones. What property makes organics behave so differently regarding magnetotransport? By studying C60 devices using several different electrode materials we show that C60, unlike many other organic semiconductors, does not exhibit any intrinsic OMAR effect. However, we find that as soon as the carriers in C60 are brought in proximity with hydrogen-containing compounds, either in the form of a polymeric electrode, or side-chain substituents, a weak OMAR effect is observed. This shows that hydrogen is crucial for the observation of OMAR.