Competing magnetic states in silicene and germanene 2D ferromagnets
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Competing magnetic states in silicene and germanene 2D ferromagnets Dmitry V. Averyanov1, Ivan S. Sokolov1, Mikhail S. Platunov2,†, Fabrice Wilhelm2, Andrei Rogalev2, Pierluigi Gargiani3, Manuel Valvidares3, Nicolas Jaouen4, Oleg E. Parfenov1, Alexander N. Taldenkov1, Igor A. Karateev1, Andrey M. Tokmachev1, and Vyacheslav G. Storchak1 () 1
National Research Center “Kurchatov Institute”, Kurchatov Sq. 1, Moscow 123182, Russia ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France 3 ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain 4 Synchrotron SOLEIL, L’Orme des Merisiers, Gyf-sur-Yvette 91192, France † Present address: Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Akademgorodok 50, bld. 38, 660036 Krasnoyarsk, Russia 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 16 June 2020 / Revised: 13 July 2020 / Accepted: 31 July 2020
ABSTRACT Two-dimension (2D) magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing. Their functionality is particularly rich when different magnetic orders are competing in the same material. Metalloxenes REX2 (RE = Eu, Gd; X = Si, Ge), silicene or germanene – heavy counterparts of graphene – coupled with a layer of rare-earth metals, evolve from three-dimension (3D) antiferromagnets in multilayer structures to 2D ferromagnets in a few monolayers. This evolution, however, does not lead to fully saturated 2D ferromagnetism, pointing at a possibility of coexisting/ competing magnetic states. Here, REX2 magnetism is explored with element-selective X-ray magnetic circular dichroism (XMCD). The measurements are carried out for GdSi2, EuSi2, GdGe2, and EuGe2 of different thicknesses down to 1 monolayer employing K absorption edges of Si and Ge as well as M and L edges of the rare-earths. They access the magnetic state in REX2 and determine the seat of magnetism, orbital, and spin contributions to the magnetic moment. High-field measurements probe remnants of the bulk antiferromagnetism in 2D REX2. The results provide a new platform for studies of complex magnetic structures in 2D materials.
KEYWORDS silicene, germanene, 2D ferromagnetism, X-ray magnetic circular dichroism (XMCD), monolayer
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Introduction
The discovery of intrinsic two-dimension (2D) ferromagnetism (FM) in layered compounds brought to the monolayer (ML) limit [1, 2] has launched a burgeoning research field exploring the fundamental physics of magnetism in reduced dimensions, emerging quantum phases, potential development of new spinrelated devices, and applications [3–5]. The material landscape of 2D ferromagnets is shaped by atomically thin crystals built upon transition metal magnetic ions Cr [1, 2], V [6, 7], Mn [8], and Fe [9, 10] as well as rare earths (REs) [11, 12]. Intrinsic 2D magnetic materials are highly amenable to external stimuli [3, 4]. Thus, 2D FM is particularly appealing once borders or coexi
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