Yttrium Iron Garnet (YIG) is an artificial Garnet (similar to the semiprecious stone) used in various microwave, acoustic, and optical devices – for instance, filtering out microwave radiation or converting electrical signals into sound (or visa versa) in a microphone. YIG is also used in certain types of lasers, and in electronic data storage. Now, research from ISIS has shown it could have the potential to form the base for a revolution in data transfer.
a) Atomic structure of YIG. b) Atomic structure of metallic iron c) A crystal of YIG
Conventional electronics is based on electrical current – the movement of charged electrons. Recently spintronics, where the quantum-mechanical spin of the electron transmits information has been seen as the potential successor to electronics. Now scientists are trying to establish whether small oscillations in the magnetic properties of YIG can be used to transmit information – a process called Magnonics.
Many applications of YIG are at room temperature, or even higher, but it is here that our fundamental understanding of the magnetic properties of YIG breaks down. At the very lowest temperatures – near to absolute zero - YIG is can be understood as a conventional ferromagnet (like a bar magnet made of metallic iron), and existing measurements (from almost 40 years ago!) are more than adequate. At room temperature, however, the complexities of YIG (shown alongside Iron in Fig 1) are much more difficult to understand.
Dr Andrew Princep and a team from Oxford University (with colleagues from the ISIS neutron and muon source, the Paul Scherrer Institut in Switzerland, and INNOVENT in Germany) have performed measurements of the complete magnetic properties of YIG. The researchers used a large, flawless crystal of YIG (equivalent to over 60 Karats, if it were a true gemstone), grown by INNOVENT. The measurements took over 200 hours on the MAPS spectrometer at ISIS, and relies on the ability of neutrons to interact with the magnetic field of the atom. Using sophisticated computer modelling techniques, the researchers were able to fully reproduce the data (Fig. 2) which tells a complicated story about the magnetic interactions between iron atoms in YIG. These results can be used to understand and predict the way YIG behaves at room temperature, which is essential in modelling the performance of devices for future applications.
Left column: Measured neutron scattering data on a crystal of YIG. The vertical axis is the amount of energy the neutron loses when scattering, and the horizontal axis is the amount of momentum lost by the neutron. Right column: the computer model.
Read the full article J. Princep et. al. “The full magnon spectrum of yttrium iron garnet" NPJ Quant. Mat. DOI: 10.1038/s41535-017-0067-y
See here for more information on the instrument MAPS or contact Dr Andrew Princep.