Tunable Room-Temperature Ferromagnet

Nature, Scientific Reports has published an article written by Aigu L. Lin, NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456 – Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3, Singapore 117542, J. N. B. Rodrigues, Chenliang Su, Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117543, M. Milletari, Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3, Singapore 117542, Kian Ping Loh, Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117543, Tom Wu, Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia, Wei Chen, Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117543, A. H. Castro Neto, Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3, Singapore 117542, Shaffique Adam Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3, Singapore 117542 – Yale-NUS College, 16 College Ave West, Singapore 138527, and Andrew T. S. Wee, NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore,28 Medical Drive, Singapore 117456 – Centre for Advanced 2D Materials and Graphene Research Centre, Faculty of Science, National University of Singapore, 6 Science Drive 2, Singapore 117546 – Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3, Singapore 117542.

The gray box represents the nanocomposite, with the blue spheres
representing the iron-oxide nanoparticles and the brown strips
representing the highly defective graphene oxide layers.
The nanocomposite’s thin film is deposited on top of a silicon dioxide substrate (in light blue). Two cobalt ferromagnetic electrodes (yellow) are placed on top of the nanocomposite. For zero applied magnetic field, these are pinned in an anti-parallel configuration by PtMn layers (in red).

Abstract : “Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011 A m²/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite.”