First-principles investigation of the emergence of multiferroicity and skyrmions in CrI2

TL;DR

This study uses first-principles calculations to explore how electronic correlations induce multiferroicity and skyrmions in CrI2, revealing mechanisms for controlling skyrmion-based memory devices.

Contribution

It demonstrates the importance of Coulomb interactions in predicting multiferroic and skyrmionic properties of CrI2, and shows how intercalation enhances these effects for spintronic applications.

Findings

CrI2 exhibits non-centrosymmetric ground state with ferroelectricity.

Dzyaloshinskii-Moriya interaction enables skyrmion formation.

Intercalation with Pt enhances DMI and polarization.

Abstract

The recently discovered van der Waals magnetic semiconductor CrI2 shows promise for spintronic applications. Its electronic and magnetic properties are known to be strongly influenced by electronic correlations. In this work, we employ density functional theory calculations where electronic correlations in CrI2 are considered within an on-site Coulomb interaction, U, with U being determined using the perturbative approach based on the linear response method. We show that the accuracy of an on-site Coulomb interaction is essential for predicting the non-centrosymmetric orthorhombic ground state of CrI2, which allows the existence of ferroelectricity and non-zero Dzyaloshinskii-Moriya (DMI) interaction. Our calculation shows that the ground state of bulk CrI2 has electric polarization of 0.15 {\mu}C/cm-2 pointing along the z-axis and the small DMI energy that changes sign with the ferroelectric polarization switching. The DMI and polarization are enhanced to 0.28 meV/formula-unit and 0.63 {\mu}C/cm-2 when Pt intercalates bilayers of CrI2, due to its large spin-orbit coupling strength and large off-center displacement. Such an enhanced DMI leads to the N\'eel skyrmions, whose handedness is controlled by ferroelectric polarization. Our work contributes to the creation and manipulation of bits in skyrmions-based memory devices.