Molecular spin channels between two ferromagnetic electrodes can produce strong exchange coupling and dramatic effect on the spin transport, thus enabling the realization of novel metamaterials. These molecule-based magnetic metamaterials can lead to futuristic logic and memory devices. To realize such device, we produced magnetic tunnel junction based molecular spintronics devices (MTJMSDs). An MTJMSD is produced by bridging the organometallic molecular clusters (OMCs) across a ~2 nm thick insulator of a magnetic tunnel junction (MTJ), along with its exposed side edges. Along the exposed edges the maximum gap between two ferromagnetic electrodes is governed by the tunnel barrier thickness. These MTJMSDs exhibited the unprecedented increase in exchange coupling between ferromagnetic films and dramatic changes in the spin transport. This paper focuses on the dramatic current suppression phenomenon exhibited by MTJMSDs at room temperature. In the event of current suppression, the effective MTJMSDs’ current reduced by as much as six orders of magnitude as compared to the leakage current level of an MTJ test bed. Current suppression phenomenon was found to be associated with the unprecedented changes in the MTJ’s magnetic properties due to OMCs. The role of OMC in changing MTJ’s properties was determined by the three different types of magnetic characterizations: SQUID Magnetometer, Ferromagnetic Resonance, and Magnetic Force Microscopy. We will also discuss our recent Monte Carlo simulation associated with the current suppression observation. These simulations provide the insights about the mechanism behind molecule induced strong exchange coupling between ferromagnetic electrodes. Our theoretical study suggests that a molecular device element has to form the antiferromagnetic coupling with the first ferromagnetic film and ferromagnetic coupling with the second ferromagnetic film to produce experimental data. Our Monte Carlo studies also provided correct orders of magnitude for the strength of exchange coupling between molecules and the ferromagnetic electrodes essential for exhibiting the molecule induced changes in MTJs.

Molecular spintronics device based magnetic metamaterials

254th National Meeting (2017)

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