Non-Technical Abstract: Modern materials science permits manufacturing of layered magnetic thin film structures where growth conditions are controlled down to the atomic scale, which in turn enables fabrication of new and potentially useful artificially designed heterosystems. This Faculty Early Career Award funds education and research on nanoscale spintronic systems and magnetic heterostructures at the University of Nebraska-Lincoln. Special emphasis is laid on the fabrication of novel spintronics devices combining memory and logical functions. In general, spintronics takes advantage from the control of electric currents via the electron spin which adds a new degree of freedom to the conventional charge based current control. Here, new functionality is based on the electric control of the interface magnetization and the resulting electrically controlled interaction between magnetoelectric and ferromagnetic thin films in close contact. State of the art technology of thin film growth is used to produce these novel devices. In addition, fundamental aspects of thermodynamics in artificial magnetic superstructures are explored. This includes the control of interlayer interaction in novel superlattices by temperature, magnetic and electric fields. These studies have applications in magnetic refrigeration technology and provide access to hitherto unexplored magnetic phases. Research and education in spintronics and nanostructuring offers key qualifications in a field which presumably will revolutionize future information technology and will have a huge impact on US economy. The complexity of this field demands new educational methods. This award funds an E-learning approach using interactive online virtual experts ("knowledge Avatars") as a new key element. An Avatar is an interactive online character communicating face to face with the user, creating an intimate relation with a virtual platform. Web-based, Avatar-guided visualizations, hypertexts combining power point shows and animations, and virtual "hands-on" experiments will provide an interactive approach to learning and are a modern platform to attract public interest in research and education at the University of Nebraska-Lincoln.
Modern materials science permits control of the composition and the morphology of layered structures on the nanoscale or even below, which in turn enables fabrication of new and potentially useful artificially designed heterosystems. This Faculty Early Career Award funds education and research on nanoscale spintronic systems and magnetic heterostructures at the University of Nebraska-Lincoln. Special emphasis is laid on the fabrication of novel spintronics devices combining memory and logical functions. Their functionality is based on the electric control of the interface magnetization in exchange bias heterosystems using molecular beam epitaxial growth of magnetoelectric/ferromagnetic exchange coupled thin films. In addition, fundamental aspects of thermodynamics in artificial magnetic superstructures are explored. This includes the control of interlayer exchange in antiferromagnetic superlattices by temperature, magnetic and electric fields. These studies aim on the creation of very large entropy changes in artificial magnetocaloric heterostructures and the control of staggered fields in artificial antiferromagnets providing access to hitherto unexplored magnetic phase transitions. Research and education in spintronics and nanostructuring offers key qualifications for the challenges involved in future technology. The complexity of this field demands new educational methods. This award funds an E-learning approach using interactive online virtual experts ("knowledge Avatars") as a new key element. An Avatar is an interactive online character communicating face to face with the user, creating an intimate relation with a virtual platform. Web-based, Avatar-guided visualizations, hypertexts combining power point shows and animations, and virtual "hands-on" experiments will provide an interactive approach to learning and are a modern platform to attract public interest in research and education at UNL.
Dr. Binek’s research focuses on new phenomena which emerge at interfaces in thin-film multilayer structures grown by molecular beam epitaxy. This methodology utilizes an ultra-high vacuum environment where controlled deposition of materials such as metals and metaloxides takes place. An essential property of this fabrication method is its potential to nanostructure materials with virtually atomic precision by utilizing low energy and low flux conditions during deposition. It enables growth of ultra-thin crystalline layers of materials in compositions and structure which otherwise cannot be synthesized in equilibrium processes. Multilayers of dissimilar materials with interfaces close to atomic sharpness become feasible. It is at those well-defined interfaces where new physical phenomena not seen in bulk materials can emerge. Dr. Binek’s group focused on interface phenomena which are magnetic in origin. An important part of the work involves the investigation of multilayers combining magnetoelectric insulating antiferromagnets and metallic ferromagnetic thin films. This work takes place in the broader context of electrically controlled magnetism and spintronic applications. The absence of direct coupling between a magnetic moment with an electric field makes the voltage-control of magnetism a scientific challenge. Voltage-controlled spintronics is of particular importance to continue progress in information technology through reduced power consumption, enhanced processing speed, integration density, and functionality in comparison with present day complementary metal-oxide semiconductor integrated electronics. Electric power consumption and production of Joule heat are a major bottleneck for optimization of microelectronic devices. It limits progress anticipated by Moore’s law while consumer and industry expectations demand for even "more than Moore". Controlling magnetism by purely electrical means, is a key challenge to better spintronics with ultra-low power consumption. Dr. Binek and company achieved robust isothermal electric control of exchange bias at room temperature ( for a popular presentation of the findings see article on NSF’s discovery page ) in a magnetic heterostructure. Exchange bias describes a shift of the magnetic hysteresis along the magnetic field axis. The so-called exchange bias effect originates from a coupling phenomenon at the interface between ferromagnetic and antiferromagnetic films. Voltage-control of this shift gives rise to a number of promising spintronic applications combining memory and logical functions. Spintronic is a technology aiming at an active exploitation of the quantum mechanical spin-degree of freedom of electrons. A goal of Dr. Binek's research is realizing spintronic devices based on voltage-controlled exchange bias . This work takes place in collaboration with colleagues of UNL’s MRSEC. In addition to the investigation of magnetoelectric interfaces, Dr. Binek explores alternatives to conventional cooling technology harnessing the magnetocaloric effect (MCE). The MCE is expected to play an important role in energy-efficient and environmentally friendly refrigeration technologies of the future. Dr. Binek and company focus on magnetocaloric materials which are cost-effective, stable, environmentally friendly, maximize the MCE in the vicinity of room-temperature, and minimize hysteretic losses (watch a video here for an introduction into Dr. Binek's work ). Dr. Binek utilizes nanotechnology by tailoring interactions within and between ultra-thin films. This work is a related to fundamental aspects of the thermodynamics of artificial antiferromagnets . Dr. Binek's group contributed also to the understanding of the exchange bias training effect. It refers to an aging phenomenon and describes the gradual decrease of the exchange bias effect with increasing cycles of hysteresis loops. Dr. Binek developed the first analytic thermodynamic theory describing the exchange bias training effect. Exchange bias training is a particular form of the more general aging phenomena. The generality of our theory is quite remarkable and important for applications depending on a persistent presence of exchange bias. A prominent example is the pinning of one of the magnetic layers in a giant magnetoresistance or tunnel magnetoresisatance read head. Applications demand heterostructures where the exchange bias remains constant after millions of magnetization reversal cycles of the sensor layer. Understanding exchange bias is therefore important for applications like read heads which are present in every modern hard disk drive. A CAREER award has also an educational component. Dr. Binek's main objectives were: -Creating an E-learning platform using interactive online characters -Implementing avatars allowing for face-to-face conversation The educational component pioneered the idea of animated avatars as interactive knowledge basis for physics education. When we suggested the approach our work was quite innovative and created substantial media attention. Using the Web to extend the classroom wasn't a new idea. However, rather than the simple posting of notes or PowerPoint presentations, we envisioned students to address questions 24/7 to a virtual instructor. Today, Web-designer create online characters for use in email, discussion groups, and online forums. One of our challenges was to equip the avatar with expert-knowledge and allowing face-to-face communication. Our hope was that student-to-avatar dialogues simulate face-to-face interaction which is the most effective way of learning. An example allowing to chat with an avatar is found here avatar with expert knowledge about the Farady effect.
