The "spiral magnetic material" in which the spins are arranged in a spiral shape is expected to be a new spintronics material that utilizes the twisting method of the spins as information.However, substances exhibiting spiral magnetism are rare, and even perovskite-type transition metal oxides, which have been studied for a long time as spintronics materials, have been reported in a limited number of cases.
This time, the research group of the University of Tokyo and Osaka University focused on cobalt oxide with a cubic perovskite-type structure.It is known that when iron oxide with the same structure and spiral magnetism stretches the bond length of iron and oxygen, the twisting of the spin arrangement changes significantly, so the bond length of cobalt and oxygen is also stretched in the same way. We aimed to search for a novel magnetic phase.
By ultra-high pressure oxidation treatment, a large single crystal of perovskite type cobalt oxide whose bond length is extended by element substitution is synthesized while maintaining a strong bond between cobalt and oxygen, which is considered to be necessary for spiral magnetism.Magnetization measurements were performed on the obtained single crystal, and it was found that the ferromagnetic phase was changed to a new magnetic phase by increasing the bond length between cobalt and oxygen by only about 1%.Furthermore, it was confirmed from experiments and theoretical calculations that this new magnetic phase is a spiral magnetic phase.
This proved for the first time in the world that even an oxide having a simple crystal structure such as cubic perovskite can generate spiral magnetism by controlling the strong bond between the transition metal and oxygen.
This result provides a new guideline that will lead to the development of new oxide spiral magnetic materials, and at the same time, the magnetic switching of ferromagnetic-spiral magnetic transition due to the increase of crystal lattice will be applied to new pressure sensors and magnetic actuators. It is expected to lead to applications.
Paper information:[Physical Review Materials] Negative-pressure-induced helimagnetism in recently cubic perovskites Sr1-xBaxCoO3