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Our business at Reciprocal Engineering - RE Ltd. is the development of genuinely ferromagnetic, insulating thin film materials, which can be used at temperatures up to 400K, and thin film devices. The materials provide a route to more efficient and significantly smaller electronics and consider the environmental aspects. It is hardly possible to meet the contemporary environmental, economic and technological boundary conditions by modifying existing materials - we design, fabricate and test new thin film materials. Several new thin film materials are currently being patented.

 

Advantages

Ferromagnetic insulators up to elevated temperatures. Materials which are ferromagnetic insulators up to 400 K can serve as a media for processing information in a form of spin waves (present in ferromagnetic media) with very low losses due to the absence of Eddy currents (they are insulators) - making the material very attractive alternative for metallic ferromagnetic layers and materials which are ferromagnetic insulators only at the lowest temperatures.

 

Alternative for rare earth element -based compounds. Our materials are RoHS-compliant: they do not contain heavy metals or six-valent chromium. Besides, they do not possess rare-earth elements or iron. Rare-earth elements are a subject to sudden price changes, though in many applications they can be replaced. Iron is a puzzling metallic impurity which is better to be avoided.

 

Application examples are in IoT-technology, such as tunable RF-devices, antenna and waveguide structures, sensors, memories and all-spin logic (ASL) devices. Iron is a major impurity in semiconductor industry and avoiding iron is a technological advantage. The challenges in semiconductor industry are described in "The International Technology Roadmap for Semiconductors 2.0.2015 Edition, Executive summary". Besides materials we design and test tunable RF-devices. Our focus is on fast, small and low-energy consuming solutions for the next generation devices operating at tens of GHz frequencies.

 

We developed, in collaboration with Oak Ridge National Laboratory, a new insulating ferromagnetic thin film material (ATO) system which, besides economic and environmental advantages, has technical merits in tunable devices. The benefits are high operating temperature range (from the lowest temperatures up to 400 K and above), simpler electronics via a lesser number of components and manufacturing via a smaller number of processing steps with high crystalline quality. The ATO films grow excellently on silicon, silicon carbide, gallium nitride and optically transparent single crystal substrates, such as lithium niobate and sapphire and suit for multilayer device manufacturing. Magnetization of a few nm thick ATO films exceeds the value found in Y3Fe5O12 (YIG). We have also developed ferromagnetic thin film insulators from common, non-magnetic cations. When compared to the bulk material comprised from the same elements, we were able to increase the magnetization value by a factor of 100. The films preserve magnetization up to elevated temperatures and can be used in practical devices. The material is compatible with several high-k materials, including the one developed by Reciprocal Engineering - RE. Materials are transparent to visible light and can be applied in magneto-optic applications.

 

The functional properties of ATO films, such as magnetization and electrical resistivity, can be adjusted during the film growth while preserving the crystal structure and atomic scale metrics. This allows the fabrication of multilayer devices without detrimental interfaces: composition can continuously be adjusted during film growth. Films suit as platforms for ASL-circuits and devices. Notably the possibility to utilize the space in three dimensions is attractive. The ability to adjust magnetization, by either composition or strain, can be applied in the control of ferromagnetic resonance frequency (FMR). FMR dictates the operating  frequency of the RF-devices. Multilayer structures are applied in sensitive magnetic field sensors and spintronic applications.

 

Advanced manufacturing. Electrodes are necessary in practical devices, and we have developed several routes to make them in-situ. We are currently developing a new route for writing complex, embedded  electrode patterns on the ATO films with high-quality lattice matching. The route simplifies the electrode manufacturing process and allows to make complex patterns in a fast and straightforward manner. Technique does not require masks.

Ferromagnetic insulators are unusual

Magnetic interactions in oxides were intensively studied by John B. Goodenough, one of three winners of the Nobel Prize in Chemistry 2019. His models explaining the direct and indirect interactions were applied in our R&D, examples of which are given in our recent paper published in the Annalen der Physik-journal. As was pointed out by P. W. Anderson in New approach to the theory of superexchange interactions. Phys. Rev. 115, 2-13 (1959), the prevailing coupling between magnetic cations in most of the compounds is antiferromagnetic, which includes also ferrimagnetic materials. This counts for the fact that ferromagnetic insulators are rare compounds, yet those operating at room-temperature are indeed unique. Correspondingly, experiments and characterizations requiring genuine insulating ferromagnets are conducted at cryogenic temperatures, thus requiring expensive techniques characteristic to well-equipped research laboratories.

 

The impact of room-temperature insulating ferromagnets on practical devices is significant.

The Nobel Prize in Physics 1977 was awarded jointly to Philip Warren Anderson, Sir Nevill Francis Mott and John Hasbrouck van Vleck "for their fundamental theoretical investigations of the electronic structure of magnetic and disordered systems".