Final Report Summary - NOMAD (Nanoscale Magnetization Dynamics)
Modern computing technology is based on writing, storing, and retrieving information encoded as magnetic bits. Key aspects of nearly all these functions concern the miniaturization of magnetic elements and the time dependence of the magnetization. Design requirements for a data storage device, for example, might specify a stability of years while simultaneously requesting write speeds in the nanosecond regime. NOMAD addressed these issues from both a short-term and a long-term perspective.
The first perspective concerned information storage in materials compatible with present-day technological applications, namely ferromagnetic metal films that are cheap and easy to fabricate. The focus was on finding novel strategies to write magnetic information in miniaturized bits using a minimum amount of power. The best and most innovative results have been obtained with methods that exploit the relativistic transformation of electric fields into magnetic fields in ferromagnetic/heavy metal bilayer films traversed by an electric current. An extremely efficient mechanism to control the switching of magnetic bits using an electric current was discovered. This mechanism, which is based on relativistic effects such as the spin Hall and Rashba spin-orbit torques, is fundamentally different from previous approaches. It yields flexible strategies for the design of non-volatile reprogrammable memory and logic applications operating on the sub-nanosecond timescale at reduced power, several of which have been patented and are currently being investigated worldwide.
The second perspective aimed at pushing the manipulation of nanomagnets down to the molecular level, replacing metal-based ferromagnets with molecules, equal to one another and with dimensions approaching one nanometer. While this strategy presents enormous advantages in terms of miniaturization, it also has major drawbacks related to the need of interfacing the molecules with solid state circuitry and stabilizing the molecular magnetic moment against electronic and thermal perturbations. The work carried out within NOMAD addressed the synthesis of two and zero-dimensional molecular aggregates on metals by self-assembly and single molecule manipulation techniques. A strong focus was on methods to control the molecular spin either by intrinsic and extrinsic charge transfer (doping) or by magnetic coupling to ferromagnetic and antiferromagnetic substrates. The results obtained in this work will help to solve outstanding problems in the field of molecular spintronics, such as the control of the molecular magnetic moment on different substrates, its stabilization against thermal fluctuations, the influence of the molecular spin on electrical transport, as well as the switching of the molecular magnetization by external means.
The first perspective concerned information storage in materials compatible with present-day technological applications, namely ferromagnetic metal films that are cheap and easy to fabricate. The focus was on finding novel strategies to write magnetic information in miniaturized bits using a minimum amount of power. The best and most innovative results have been obtained with methods that exploit the relativistic transformation of electric fields into magnetic fields in ferromagnetic/heavy metal bilayer films traversed by an electric current. An extremely efficient mechanism to control the switching of magnetic bits using an electric current was discovered. This mechanism, which is based on relativistic effects such as the spin Hall and Rashba spin-orbit torques, is fundamentally different from previous approaches. It yields flexible strategies for the design of non-volatile reprogrammable memory and logic applications operating on the sub-nanosecond timescale at reduced power, several of which have been patented and are currently being investigated worldwide.
The second perspective aimed at pushing the manipulation of nanomagnets down to the molecular level, replacing metal-based ferromagnets with molecules, equal to one another and with dimensions approaching one nanometer. While this strategy presents enormous advantages in terms of miniaturization, it also has major drawbacks related to the need of interfacing the molecules with solid state circuitry and stabilizing the molecular magnetic moment against electronic and thermal perturbations. The work carried out within NOMAD addressed the synthesis of two and zero-dimensional molecular aggregates on metals by self-assembly and single molecule manipulation techniques. A strong focus was on methods to control the molecular spin either by intrinsic and extrinsic charge transfer (doping) or by magnetic coupling to ferromagnetic and antiferromagnetic substrates. The results obtained in this work will help to solve outstanding problems in the field of molecular spintronics, such as the control of the molecular magnetic moment on different substrates, its stabilization against thermal fluctuations, the influence of the molecular spin on electrical transport, as well as the switching of the molecular magnetization by external means.