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- Defect for Defect's Sake: Ideal Material Found for Gadgets and Auto Electronics Chips
Defect for Defect's Sake: Ideal Material Found for Gadgets and Auto Electronics Chips
Russian scientists, together with colleagues from Taiwan and Indonesia, have studied the properties of nickel ferrite and found that some of them can change due to the presence of point defects in the structure of the compound. This is useful for the development of fast and non-volatile electronic devices, in particular chips resistive memory, which may find application in auto electronics, the Internet of Things and wearable gadgets. Read more about the research in the Izvestia article.
Resistive memorydevices
Specialists from MIPT and the Joint Institute of High Temperatures (JIHT) RAS together with colleagues from Taiwan and Indonesia studied the structural and sensitive properties of nickel ferrite. This material - a complex oxide of iron and nickel - is a dark brown crystals insoluble in water, is characterized by mechanical hardness and chemical stability, as well as has a high resistivity and Curie temperature (the temperature above which magnetic materials lose their ferromagnetic properties, being replaced by paramagnetism) more than 500 °C. Until it is reached, the phase state and magnetic properties do not change, therefore, nickel ferrite easily withstands the effect of high temperatures.
It was found that the properties of this material can change due to the presence of point defects in the structure of the compound. Due to this nickel ferrite - a promising material for spintronics and the production of chips resistive memory, told "Izvestia" in MIPT. The research results will be useful for the development of fast and non-volatile electronic devices.
Vladimir Stegailov, Head of the Laboratory of Supercomputing Methods in Condensed State Physics, MIPT
According to scientists, practically significant properties of nickel ferrite are structurally sensitive. They strongly depend on the presence of defects in the crystal, i.e. violations in the periodicity of atomic arrangement. Scientists from MIPT and OIVT RAS together with foreign colleagues studied the structure of the ideal crystal of nickel ferrite and the real one with point defects.
The specialists used methods of first-principles calculations of electronic structure, which are based on the apparatus of quantum physics, but do not involve empirical parameters and are characterized by mathematical rigor.
Also in the course of the work the motion of polarons in the structure of nickel ferrite was studied. A polaron is a quasi-particle consisting of an electron and a polarization field caused by the deformation of the crystal lattice during the movement of the electron itself. Scientists have found that polaron conductivity depends on the presence in the structure of nickel ferrite of oxygen vacancies - free spaces that can be occupied - and antisite defects observed when the nickel cation is in the iron position.
- Showed the change of polaronnoy conductivity from electronic to hole (conductivity of a semiconductor in which the main carriers of electric current become holes) in the structure of nickel ferrite, which has defects in the form of oxygen vacancies and antisite nickel - said the head of the laboratory of supercomputer methods in condensed matter physics MIPT Vladimir Stegailov.
In this study, scientists have found that in crystals of nickel ferrite can be formed, as if threads, conduction channels of double oxygen vacancies. Such channels are called filaments. Because of their appearance and increases the hole conductivity.
In solid state physics, a hole is the absence of an electron in an almost completely filled valence band. In a sense, the behavior of a hole in a semiconductor is similar to the behavior of a bubble in a full bottle of water.
How nickel defects can help create new microchips
As the researchers explained, spin devices use the electron's spin - its intrinsic momentum - along with its charge, which, like a magnet, creates a magnetic field around it, so its orientation can be changed by external influence. Resistive memory has the speed of RAM, but also retains data in the event of a power failure, like an external disk. Resistive memory chips are based on the structure: metal - insulator - metal.
It can be expected that complex calculations of the electronic structure of nickel ferrite and similar materials, made by a group of Russian and foreign scientists, will contribute to the development of fast electronic devices, the scientists emphasized.
The research opens the way to the creation of non-volatile resistive memory chips, where conductivity control is carried out through the formation of conductive filaments, said Vasily Chaly, a laboratory assistant at the Center of Competence NTI "Digital Materials Science: New Materials and Substances" Bauman Moscow State Technical University.
- Such devices combine the speed of RAM and reliability of data storage, which makes them promising for use in car electronics, wearable gadgets, as well as in Internet of Things systems and other energy-dependent applications where resistance to extreme conditions is important," he said.
The calculations performed and the results obtained are certainly of scientific interest. However, there is a huge difference between systems that can be studied by the density functional method and real samples that are studied in experiment, and even more so used in modern technological processes, said Valery Uzdin, Professor of the Physics Department of ITMO, Doctor of Physical and Mathematical Sciences.
- It can be said that the conducted research is only the first steps in this direction. However, if you don't take them, you can't go all the way," the expert said.
The research results were published in the journal Computational Materials Science.
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