Giant magnetoresistance in ferromagnet/organic semiconductor/ferromagnet heterojunctions

Abstract

We report the spin injection and transport in ferromagnet/organic semiconductor/ferromagnet ͑FM/OSC/FM͒ heterojunctions using rubrene ͑C 42 H 28 ͒ as an organic semiconductor spacer. For completeness of our study, both tunneling magnetoresistance ͑TMR͒ and giant magnetoresistance ͑GMR͒ were studied by varying the thickness of the rubrene layer ͑5-30 nm͒. A thorough study of the device characteristics reveals spin-polarized carrier injection into and subsequent transport through the OSC layer. When the thickness of the rubrene layers are beyond the tunneling limit, the device currents are limited by carrier injection and bulk transport. The carrier injection is well described with phonon-assisted field emission. The behavior of GMR in response to bias field and temperature shows significant differences from that of TMR.

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

“…However, very few experiments have been done with a systematic characterization of the magnetic and electrical properties of many devices. A very comprehensive set of measurements on LSMO/LAO/Alq 3 / Fe spin-valves was reported by Yoo et al [37]. These authors varied the thickness of a rubrene layer between 5 and 50 nm and were able to distinguish between the tunneling and hopping regimes discussed above.…”

“…Clearly, it is also possible to change the FM-OSC coupling by the use of thin interfacial layers. The effect of a tunnel barrier between the metal and the OSC on the functionality of a spin-valve device has proven to be critical for spin-polarized tunneling [33,37,38,[46][47][48][49]. Dediu and coworkers have demonstrated that the quality of the metalorganic interfaces can be improved by inserting an Al 2 O 3 layer on top of the organic material, prior to growing the top ferromagnetic electrode [50].…”

Room-temperature organic-based spin polarizer

“…3-5) and rubrene (C 42 H 28 ). [6][7][8] However, there is a fundamental problem so-called "conductivity mismatch" for spin injection from ferromagnetic metals into semiconductors. 9 The development of organic-based magnets is promising to provide a pathway to circumvent this problem.…”

“…7 At low temperature and low bias voltage, the device current is dominated by tunneling through defect states in the energy gap. 7 The carriers in these defect states could enter HOMO/LUMO levels via strong electric field as we increase the bias voltage, leading to the increase of the device current. At higher temperature, phonon interaction, such as phonon-assisted field emission, 7 starts to play a role, giving rise to the temperature dependence.…”

Development of Giant Magnetoresistance Material Based on Cobalt Ferrite

“…Until now, the GMR material is still experience the process of research and development by the researcher. These materials are; metal [1], alloy [2,3], semiconductors [4], organic semiconductors [5] and magnetic oxide [6,7].…”