Room-temperature ferromagnetism in CrTe2 thin flakes imaged by single spin magnetometry

Abstract

Even if magnetic van der Waals crystals where known since decades, two-dimensional (2D) magnetism has been obtained experimentally only a few years ago[1]. Since its discovery in Cr2Ge2Te6 and CrI3, an intense research effort has started, triggered by their high potential in studying 2D magnetic states[2-4]. A wide range of new physical properties emerging from the reduced dimensionality can be explored and exploited like the control of magnetic properties through gating. New devices based on van der Waals magnetic heterostructures have been proposed, such as spin-filter magnetic tunnel junctions based on CrI3 heterostructures, showing a tunneling magnetoresistance higher than their counterparts based on conventionally grown magnetic thin films. The potential of 2D magnets in topological spintronics is also under investigation, with for example recent works on the stabilization of skyrmions in Fe3GeTe2. However, in order to use van der Waals magnets as building blocks for relevant spintronics devices, a magnetic material with a Curie temperature (TC) above room temperature is required. Unfortunately, most of the available van der Waals magnets have a low intrinsic TC. Even though a 2D magnetic state at room temperature can be achieved through gating for example, it remains a challenging task and only few materials are reported to have a TC above 300K down to the monolayer limit, like MnSex, VSe2 and more recently for few-layers CrTe2[5]. Here, we report our work on CrTe2 from bulk to 40nm thin mechanically exfoliated flakes using Nitrogen-Vacancy (NV) magnetometry, a well-suited technique for the study of 2D magnets[6]. We find an in-plane ferromagnetic order at room temperature and we extract a value for the saturation magnetization Ms of 24.5 ± 3.0 kAm-1 at room temperature.