Hysteretic magnetoresistance in polymeric diodes

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2009-10, Vol.3 (7-8), p.242-244
• Main Authors: Majumdar, Sayani, Majumdar, Himadri S., Aarnio, Harri, Österbacka, Ronald
• Format: Article
• Language: English
• Subjects: 73.40.Sx; 73.61.Ph; 75.47.Pq; 85.75.Ss; Diodes; Ferromagnetism; Hysteresis; Magnetic fields; Magnetoresistance; Magnetoresistivity; Polymers; Time delay
• ISSN: 1862-6254; 1862-6270; 1862-6270
• DOI: 10.1002/pssr.200903193

We report on hysteretic organic magnetoresistance (OMAR) in polymeric diodes. We found that magnitude and lineshape of OMAR depend strongly on the scan speed of the magnetic field and on the time delay between two successive measurements. The time‐dependent OMAR phenomenon is universal for diodes made with various polymers. However, the width and magnitude of OMAR varied with the polymeric material. The suggestive reason for this hysteretic behavior is trapped carriers, which in presence of a magnetic field change the ferromagnetic ground‐state of the polymer leading to a long spin relaxation time. These experimental observations are significant for clarification of the OMAR phenomenon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) This article reports on the observation of magneto‐transport hysteresis in polymeric diodes which was otherwise absent in the I–V characteristics in absence of magnetic field. The organic magnetoresistance (OMAR) magnitude and lineshape are found to depend strongly on the scan speed of the magnetic field and on the time delay between two successive measurements. These results underline the importance of necessary precautions for the OMAR measurements and the interpretation of the data.