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Interface-engineered templates for molecular spin memory devices



The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices1,2, opening avenues for developing multifunctional molecular spintronics3. Such ideas have been researched extensively, using single-molecule magnets4,5 and molecules with a metal ion6 or nitrogen vacancy7 as localized spin-carrying centres for storage and for realizing logic operations8. However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task9. In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl10, have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli11,12 (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets13. Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development.

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Figure 1: Interface magnetoresistance effect.
Figure 2: Confirmation of IMR.
Figure 3: Interface switching response and interface model.
Figure 4: Spin-filter effect and interface MAE.

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We thank J. M. D. Coey of Trinity College, Ireland, for discussions. K.V.R. and J.S.M. were supported by the Office of Naval Research (ONR grant N00014-09-1-0177) and the National Science Foundation (grants DMR 0504158 and ULFR 09-0532-01). A.M.K. thanks the University of Groningen for partial financial support during his stay at MIT. N.A. and V.C. thank the Julich Supercomputing Centre, Forschungszentrum Julich (Germany), for performing calculations on JUROPA and JUGENE supercomputers. A.M. and T.K.S. thank IISER-Kolkata and CSIR, India, respectively, for research fellowships. S.K.M. thanks CSIR (sanction no. 01(2369)/10/EMR-II), India, for financial support. M.M. thanks the German Science foundation for support within SFB 602 and SPP 1538, and S. Demeshko for SQUID measurements. D.S. and R.M. thank the Deutsche Forschungsgemeinschaft (DFG) Priority Programme 1178 and the Danish National Research Foundation (DNRF) funded Center for Materials Crystallography (CMC) for support, and the Land Niedersachsen for providing a fellowship in the Catalysis for Sustainable Synthesis (CaSuS) Ph.D. program. J.S.M., M.M, S.K.M. and D.S. thank the Göttingen-Kolkata ‘Open shell systems (G-KOSS)’ initiative for supporting the collaboration.

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Authors and Affiliations



S.K.M., M.M. and J.S.M. designed the original research approach; A.M. and S.K.M. developed molecule synthesis; A.M.K., A.M., T.K.S., S.K.M., R.M. and D.S. performed material characterization; K.V.R. and A.M.K. prepared devices, performed transport experiments and analysed transport and magnetic characterization; N.A., P.L. and V.C. performed DFT calculations; K.V.R., A.M.K., N.A. and J.S.M. developed the organic spin-filter model; K.V.R., N.A. and J.S.M. developed the interface magnetic anisotropy model; K.V.R. coordinated collaboration; K.V.R., J.S.M. and M.M. wrote the manuscript; N.A., A.M.K., A.M. and S.K.M. provided the discussion and contributed to manuscript preparation. All authors discussed the experiments and commented on the manuscript.

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Correspondence to Karthik V. Raman, Nicolae Atodiresei, Swadhin K. Mandal or Jagadeesh S. Moodera.

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The authors declare no competing financial interests.

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Raman, K., Kamerbeek, A., Mukherjee, A. et al. Interface-engineered templates for molecular spin memory devices. Nature 493, 509–513 (2013).

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