Magnetic anisotropy and spin-polarized two-dimensional electron gas in the van der Waals ferromagnet Cr2Ge2Te6

Abstract

We report a comprehensive experimental investigation on the magnetic anisotropy in bulk single crystals of Cr2Ge2Te6, a quasi-two-dimensional ferromagnet belonging to the family of magnetic layered transition metal trichalcogenides that have attracted recently a big deal of interest with regard to the fundamental and applied aspects of two-dimensional magnetism. For this purpose electron spin resonance (ESR) and ferromagnetic resonance (FMR) measurements have been carried out over a wide frequency and temperature range. A gradual change in the angular dependence of the ESR linewidth at temperatures above the ferromagnetic transition temperature Tc reveals the development of two-dimensional spin correlations in the vicinity of Tc thereby proving the intrinsically low-dimensional character of spin dynamics in Cr2Ge2Te6. Angular and frequency dependent measurements in the ferromagnetic phase clearly show an easy-axis type anisotropy of this compound. Furthermore, these experiments are compared with simulations based on a phenomenological approach, which takes into account results of static magnetization measurements as well as high temperature g factors obtained from ESR spectroscopy in the paramagnetic phase. As a result the determined magnetocrystalline anisotropy energy density (MAE) KU is (0.48 ± 0.02) × 10 6 erg/cm 3 . This analysis is complemented by density functional calculations which yield the experimental MAE value for a particular value of the electronic correlation strength U . The analysis of the electronic structure reveals that the low-lying conduction band carries almost completely spin-polarized, quasihomogeneous, two-dimensional states. arXiv:1810.02560v3 [cond-mat.str-el]

Magnetic anisotropy and low-field magnetic phase diagram of the quasi-two-dimensional ferromagnet Cr2Ge2Te6

“…From the high-field region, a saturation magnetization of M S ≈ 3 µ B /Cr is obtained for both orientations. Thus, Cr 3+ with S = 3/2 leads to an isotropic Landé factor of g ≈ 2, which is in excellent agreement with recent results from FMR studies on this compound 27 . The saturation field is found as the x -component of the intercept of two linear fits, one being a fit to the saturated regime at high fields and one being a fit of the unsaturated linear regime at low fields.…”

“…However, around 100 K the a-axis starts to increase towards lower temperatures while the c-axis shrinks further. The increase of the a-parameter leads to a value of 6.820Å at 5 K which is larger than 6.812Å at 270 K. The temperature-onset of the increase of the aaxis with approximately 100 K agrees well with the temperatures which showed first low dimensional magnetic contributions to the linewidth in ESR experiments 27 and with Θ CW obtained in Fig. 3(c).…”

First‐Principles Prediction of a New Family of Layered Topological Insulators

“…The inplane lattice constants of the TIs range from about 6.7 to 7.5 Å, covering the lattice regions of Cr 2 Ge 2 Te 6 and CrI 3 , which are typically around 7.0 Å . Cr 2 Ge 2 Te 6 and CrI 3 are vdW‐layered ferromagnetic insulators (FMIs) that have attracted very much attention recently.…”

“…These TIs have large energy gaps enough for room temperature utilizations. Their lattice constants vary from 6.7 to 7.5 Å, covering the lattice range of Cr 2 Ge 2 Te 6 and CrI 3 . Hence, they are promising candidates to study the topological‐magnetic proximity effect with Cr 2 Ge 2 Te 6 and CrI 3 .…”

Electronic structure and magnetic properties of few-layer Cr 2 Ge 2 Te 6 : the key role of nonlocal electron–electron interaction effects

“…Electron spin resonance and ferromagnetic resonance measurements have been carried out in bulk Cr 2 Ge 2 Te 6 over a wide frequency and temperature range [113][114][115][116] , revealing the development of 2D spin correlations in the vicinity of T C and proving the intrinsically lowdimensional character of spin dynamics in this material. Such experiments returned a MAE of ∼ 50-90 µeV/Cr, which is on the same order of what estimated in Ref.…”