The movement of electrons can have a significantly greater influence on spintronic effects than previously assumed. This discovery was made by an international team of researchers led by physicists from Martin Luther University in Halle-Wittenberg (MLU). Until now, the calculation of these effects mainly took into account the spin of the electrons. The study was published in the journal “Physical Review Research” and proposes a new approach in the development of spintronic components.
Many technical devices are based on conventional semiconductor electronics. Charge currents are used to store and process information in these components. However, this electric current generates heat and energy is lost. To work around this problem, spintronics uses a fundamental property of electrons called spin. “This is an intrinsic angular momentum, which can be imagined as a rotational movement of the electron around its own axis,” explains Dr Annika Johansson, physicist at MLU. The spin is related to a magnetic moment which, in addition to the charge of the electrons, could be used in a new generation of fast and energy efficient components.
To achieve this, an efficient conversion between charge and spin currents is required. This conversion is made possible by the Edelstein effect: by applying an electric field, a charging current is generated in a material that was originally non-magnetic. In addition, the spins of the electrons align and the material becomes magnetic. “Previous articles on the Edelstein effect have mainly focused on how the spin of electrons contributes to magnetization, but electrons can also carry an orbital moment that also contributes to magnetization. If the spin is the intrinsic rotation of the electron, then the orbital moment is the motion around the nucleus of the atom, “says Johansson. This is similar to the earth, which rotates both on its own axis and around the sun. Like spin, this orbital moment generates a magnetic moment.
In this latest study, the researchers used simulations to study the interface between two oxide materials commonly used in spintronics. “Although both materials are insulators, a metallic electron gas is present at their interface which is known for its efficient charge-to-spin conversion,” explains Johansson. The team also took into account the orbital moment in the calculation of the Edelstein effect and found that its contribution to the Edelstein effect is at least an order of magnitude greater than that of the spin. These findings could help increase the efficiency of spintronic components.
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