Manipulating multi-state magnetic structures with spin currents
Manipulating multi-state magnetic structures with spin currents
Spintronic is a thriving research field which explores routes of developing novel electronic devices which utilize not only the charge of the electron but also the fact that each electron is also a tiny magnet called spin. One of the most important contributions of spintronics has been the development of magnetic random access memory (MRAM) which is a high-endurance high-retention memory which is also fast and non-volatile. The basic memory unit in MRAM is a magnetic tunnel junction which consists of two ferromagnetic layers separated by a thin insulating layer. The magnetization in the magnetic tunnel junction is either parallel or anti-parallel corresponding to its two memory states.
An important requirement for MRAM is an efficient and scalable method to manipulate the magnetic orientation of one of the ferromagnetic structure on a sub-micron scale. Early MRAM devices used magnetic fields generated around a wire which carries electrical current to achieve such manipulation; however, this method has been largely abandoned due to lack of scalability which means that the magnitude of the required electrical current needed for such manipulation does not decrease with the decrease in the size of the spintronics devices. The subsequent chosen method for magnetic manipulation was the injection of electrical current where the electrons are spin polarized; namely, the average direction of their magnetic moment is non-zero. This method is scalable; however, it is increasingly realized that charge current injection is potentially detrimental to magnetic tunnel junctions. Consequently, there is an increasing interest shifting from the use of charge currents to spin currents which are efficiently generated in heavy metal/ferromagnetic heterostructures.
Now the group of Prof. Klein from the physics department and the nanotechnology center at Bar-Ilan University has demonstrated that such spin currents can be used to efficiently switch complex magnetic structures with multiple states, paving the way for a novel type of magnetic memory with more than two states. This will enable a significant increase in the memory density of MRAM and the development of other types of spintronic devices. The research is part of the postdoctoral research of Dr. Shubhankar Das under the supervision of Prof. Klein and it has been recently published in the Nature journal Scientific Reports.
