Electrostatically controlled spin polarization in Graphene CrSBr magnetic proximity heterostructures

• Maxen Cosset-Chéneau (University of Groningen)

Date

Friday 25 October 2024

Time

14:45 - 15:15 hour

Address

Gorlaeus Building
Einsteinweg 55
2333 CC Leiden

Room

BM.1.23

Boxuan Yang^a, Bibek Bhujel^a, Daniel G. Chica^b, Evan J. Telford^b, Xavier Roy^b, Fatima Ibrahim^c, Mairbek Chshiev^c, Maxen Cosset-Chéneau^a & Bart J. van Wees^a

^a Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
^b Department of Physics and Chemistry, Columbia University, New York, NY 10027, USA.
^c Univ. Grenoble Alpes, CEA, CNRS, Spintec, Grenoble 38000, France

Abstract

Spintronics relies on 3d ferromagnets to propose devices used to store information in an energy efficient manner. These devices are composed of two neighboring ferromagnetic bilayers, which magnetization configurations are used to store the information. These magnetic states are readout by magnetoresistive effects which uses the polarization of the ferromagnet density of state at the Fermi level induced by the exchange interaction.  Although the readout of the information in these devices can be done efficiently with a limited energy dissipation, writing the magnetic information remains challenging. It indeed necessitates the reversal of a ferromagnetic layer magnetization using energy consuming processes [1]. This has led to efforts toward the electrostatic control of the ferromagnets magnetization, which would solve these limitations of spintronic devices.

This electrostatic control of the magnetization cannot be achieved efficiently in 3d ferromagnets owing to their large carrier density. In contrast, graphene displays a metallic behavior, which is electrostatically tunable thanks to its low density of states. However, pristine graphene lacks the magnetic properties allowing its use for information storage in spintronics devices. The magnetic proximity effect has changed this paradigm. It has been demonstrated that having graphene in contact with a ferromagnetic material induces an exchange splitting in its band structure. This opens the possibility to use this material as an electrostatically controllable magnetic component of spintronic devices, in which the density of state polarization at the Fermi level could be controlled by a gate voltage.

In this talk we use high field magnetotransport measurements in the quantum Hall regime to show [2] that interfacing graphene with the semiconducting antiferromagnet CrSBr results in an exchange field of 30 meV in the graphene band structure. We then demonstrate that the sign and amplitude of the spin polarization at the Fermi level in proximitized graphene can be controlled by a gate voltage, reaching values between -50% and +69%. These results thus pave the way toward the inclusion of graphene in spintronic memory devices in which both the information readout and writing could be performed in an energy-efficient manner.

References

1. Dieny, B. et al. Opportunities and challenges for spintronics in the microelectronics industry. Nat. Electron. 3, 446–459 (2020).
2. B. Yang et al. Electrostatically controlled spin polarization in Graphene-CrSBr magnetic proximity heterostructures. Nat Commun 15, 4459 (2024)