The research group of Professor Naomi Yokotani of the Graduate School of Natural Sciences, Okayama University has revealed that chromium dioxide becomes a special state of half metal at low temperatures.It is said that half metal can be used for a technology called spintronics.Today's computers use electric current to operate, but they have the problem of generating extra heat.On the other hand, spintronics is attracting attention as an information transmission technology that does not generate heat.It is a technology that utilizes the spin of electrons in a substance.

The electrons in a substance have either upward or downward spins, but in many substances, the upward and downward spins are paired and cancel each other out.On the other hand, some substances have different numbers of spins, and one of the spins remains.In particular, the state in which the spins of free electrons related to electrical conduction remain is called half metal.

So far, we have known that cryogenic chromium dioxide has significantly different spin numbers, but there is no evidence that it is a half metal.To confirm this, it is necessary to directly examine the state of spin in the substance.This was done with a device called a bulk sensitive spin-resolved photoelectron spectrometer built at Okayama University.This revealed that the difference in spin numbers is due to free electrons, that is, chromium dioxide is a half metal.We also found that spin decreased when the temperature was raised to room temperature.Chromium dioxide can only become a half metal at very low temperatures, but it will be an important clue in achieving spintronics at room temperature.

If spintronics can be realized and wasteful heat generation can be reduced, the energy problem, which is an important issue for humankind as a whole, will make great strides.As a first step, it is indispensable to know the phenomena and the properties of substances related to new technologies.

Source:[Okayama University] The world's first elucidation of the unique electronic structure of chromium oxides

Okayama University

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