Spintronics

Current technology

Most electronic devices today rely on charge transfer, where an electric current is generated by moving electrons.

Spintronics is a modern field of electronics that explores the intrinsic spin of electrons and their associated magnetic moments, in addition to their electronic charge. This technology leverages the quantum property of electron spin to manipulate and detect information, enabling new types of electronic devices that traditional electronics cannot achieve. This approach offers possibilities for creating high-performance magnetic field sensors, high-density data storage devices with faster switching rates, ultra-high frequency nanogenerators, and new computation methods leveraging quantum coherence effects.

Platinum-group metals (Pd, Pt, Ru, Rh, Ir, Os) exhibit strong spin-orbit coupling properties. When these metals interact with thin magnetic films measuring several atoms thick (e.g. Co, Ni, Fe or their alloys), they can significantly alter the system’s electronic and magnetic properties.

Key promising spintronic applications:

• MRAM devices
  Palladium could be used in magnetising layers for memory cell contacts, thanks to its low coercive force, which simplifies magnetisation and demagnetisation. This enables data writing using minimal current. Magnetoresistive memory relies on resistance changes based on electron spin orientations. Memory cells contain two ferromagnetic layers separated by a thin barrier. Their alignment (parallel or antiparallel) corresponds to binary states (‘0’ and ‘1’) with distinct resistance levels.
• Spin field-effect transistors (spinFETs)
  Its low coercive force and high magnetic susceptibility could make palladium a promising material for making spin field-effect transistors (spinFETs), which use electron spin effects to control current. In spinFET devices, palladium is used to create a magnetising layer for the channel region. The source-drain channel is made of a ferromagnetic material. The gate is used to control the channel magnetisation state, which switches over when voltage is applied on the gate. This, in turn, changes the spin polarisation of electrons flowing through the channel and hence the current through the transistor.
• Emerging technologies
  The lineup of palladium-based spintronics solutions available today is further supplemented with prototype devices such as high-performance magnetic field sensors, spin field-effect diodes, and controllable microwave nanogenerators.
• Topological semimetals
  An exciting avenue is the development of devices based on chiral topological semimetals – quantum materials with spiral atomic structures. Discovered in 2019, these materials selectively conduct current on their surfaces. Palladium can serve as a key component in these materials, enabling new quantum technologies.

Market

The market for MRAM devices based on spintronics is expected to grow significantly due to their high performance and energy efficiency. MRAM technology combines the speed of DRAM with the non-volatility of flash memory. As demand for faster and more reliable data storage solutions increases across sectors like cloud computing and IoT, MRAM could become a dominant player in the spintronics market.

Challenges of current technology

Existing competitors in the memory device market face challenges such as energy dependence (e.g. DRAM) or slower access times compared to MRAM. Traditional memory technologies like DRAM require constant power supply to retain data, whereas MRAM offers non-volatility without sacrificing speed.

Positive impact of palladium

Palladium, a transition metal, stands out due to its excellent conductivity, corrosion resistance, and compatibility with existing industrial processes. While pure palladium is paramagnetic, introducing minimal magnetic impurities (up to 3 ppm) induces ferromagnetic properties. Among group 2 transition metals, palladium exhibits the highest electron density and magnetic moment per atom of iron, as well as a magnetic susceptibility six times higher than platinum. These attributes position palladium as a promising material for spintronic applications.

Palladium’s unique electronic structure and magnetic properties offer new opportunities for advancing electronics, paving the way for innovative materials and devices to shape future technologies.

To find out more about the physical qualities of palladium, see – Chemistry.

To find out more about palladium in spintronics, see the following scientific publications:

Lyu, D., Shoup, J. E., Huang, D., García‐Barriocanal, J., Jia, Q., Echtenkamp, W., … & Wang, J. P. (2023). Sputtered L10‐FePd and its Synthetic Antiferromagnet on Si/SiO2 Wafers for Scalable Spintronics. Advanced functional materials, 33(18), 2214201. DOI: https://doi.org/10.1002/adfm.202214201

Luong, N. H., Trung, T. T., Hong, T. T., Nam, N. H., Phan, M. H., Jenei, P., … & Gubicza, J. (2022). Relating the magnetic coercivity to the L10 ordered FePd phase in annealed FexPd100-x nanoparticles. Applied Physics A, 128(10), 936. DOI: https://doi.org/10.1007/s00339-022-06059-x

Seifert, T., Jaiswal, S., Martens, U., Hannegan, J., Braun, L., Maldonado, P., … & Kampfrath, T. (2016). Efficient metallic spintronic emitters of ultrabroadband terahertz radiation. Nature photonics, 10(7), 483-488. DOI: https://doi.org/10.1038/nphoton.2016.91

Li, Y., Loh, L., Li, S., Chen, L., Li, B., Bosman, M., & Ang, K. W. (2021). Anomalous resistive switching in memristors based on two-dimensional palladium diselenide using heterophase grain boundaries. Nature Electronics, 4(5), 348-356. DOI: https://doi.org/10.1038/s41928-021-00573-1

Yang, Q., Li, G., Zhang, Y., Liu, J., Rao, J., Heine, T., … & Sun, Y. (2021). Transition metal on topological chiral semimetal PdGa with tailored hydrogen adsorption and reduction. npj Computational Materials, 7(1), 207. DOI: https://doi.org/10.1038/s41524-021-00684-5