Perovskites are defined by their special cubic crystal structure. They form a family of materials with many interesting properties, e.g., they are inexpensive to produce, have excellent light-emission properties, and can be tailored for various applications. They are used for solar cells, light-emitting diodes, and other applications.

A type of perovskite containing halogens and lead has recently shown interesting magnetic properties, which opens up the possibility of using them in spintronics. The use of lead, however, has limited the development of the material for health and environmental reasons.

Spintronics is the field of technology in which information about the direction of rotation of a particle (its spin) is stored, not just its charge. Spintronics is said to have enormous potential for the next generation of information technology, since information can be transmitted at higher speeds and with lower energy consumption.

Feng Gao, Linköping University, Sweden, and colleagues have developed an optoelectronic magnetic double perovskite without lead. The team started with the benchmark double perovskite Cs₂AgBiBr₆, which is a promising lead-free and stable optoelectronic material. They used magnetic element iron alloying to develop a new generation of materials that can potentially couple optoelectronics with spintronics. The researchers found that Fe³⁺ is replacing Bi³⁺ and forming FeBr₆ clusters, which homogenously distribute throughout the double perovskite crystals. The double perovskite alloy, Cs₂Ag(Bi:Fe)Br₆, shows a structural phase transition at ~120 K and a strongly temperature-dependent magnetic response at temperatures below 30 K (-243.15 °C).

The researchers suspect that the magnetic response is due to a weak ferromagnetic or antiferromagnetic response from localized regions. If this is true, this is a class of new materials for future information technology. But further research is needed, not least to preserve the magnetic properties at higher temperatures, the researchers say.

• Magnetizing Lead-Free Halide Double Perovskites,
  Weihua Ning, Jinke Bao, Yuttapoom Puttisong, Fabrizo Moro, Libor Kobera, Seiya Shimono, Linqin Wang, Fuxiang Ji, Maria Cuartero, Shogo Kawaguchi, Sabina Abbrent, Hiroki Ishibashi, Roland the Marco, Irina A. Bouianova, Gaston A. Crespo, Yoshiki Kubota, Jiri Brus, Duck Young Chung, Licheng Sun, Weimin M. Chen, Mercouri Kanatzidis, Feng Gao,
  Science Advances 2020.
  https://doi.org/10.1126/sciadv.abb5381