Apparent Ferromagnetism in Exfoliated Ultrathin Pyrite Sheets

Abstract

There has been no experimental evidence for ferromagnetic ordering in isotropic atomically thin two-dimensional crystals, until a bilayer Cr 2 Ge 2 Te 6 and a three-atom thick monolayer CrI 3 is shown to retain ferromagnetic ordering at finite temperatures. Here, we demonstrate successful isolation of a nonvan der Waals-type ultrathin nanosheet of FeS 2 derived from naturally occurring pyrite mineral (FeS 2 ) by means of liquid-phase exfoliation. Structural characterizations imply that (111)-oriented sheets are predominant and are supported theoretically by means of density functional theory surface energy calculations. Spinpolarized density theory calculations further predicted that (111)oriented three-atom thick pyrite sheets have a stable ferromagnetic ground state different from their diamagnetic bulk counterparts. This theoretical finding is evaluated by experimentally employing low-temperature superconducting quantum interference device measurements, and an anomalous ferromagnetic kind of behavior is observed.

Unraveling complex magnetism in two-dimensional FeS$_2$

“…Our calculated spin spiral energies using generalized Bloch theorem and also supported by the results from Monte Carlo simulations indicate that the magnetic ground states of the ground state structural phase are not perfectly collinear. During the revision of this paper, the experimental paper are published in JPCC [29]. The authors revised the results as they point out that they observed the ferromagnetic phase, but it only appears at low temperature, which is consistent with our theoretical studies.…”

“…In the past, dynamical stability, electronic and magnetic properties of 2D FeS 2 with different surface orientations have been investigated theoretically [23][24][25][26][27]. Very recently, Anand et al have reported the isolation of 2D FeS 2 , and more importantly, they found that it is possible to observe long-range ferromagnetic (FM) order even up to room temperature [28,29]. Their DFT simulations show that the FeS 2 (111) surface is the one that has the lowest formation energy and at the same time has FM configuration as the ground state.…”

Liquid‐Phase Exfoliation of Nonlayered Non‐Van‐Der‐Waals Crystals into Nanoplatelets

“…[ 68 ] This work is then followed by the exfoliation of many other minerals such as chromite, [ 70 ] ilmenite, [ 69 ] goethite, [ 75 ] galena, [ 75 ] calcite, [ 75 ] and pyrite. [ 81,82 ]…”

Integrating ferromagnetism and ferroelectricity in an iron chalcogenide monolayer: a first-principles study

“…[30][31][32] 2D FeS 2 has been demonstrated to show ferromagnetic (FM) order at room temperature. 33,34 The symmetry-breaking 2D FeTe 2 is predicted to show excellent stability and room temperature ferromagnetism. 35,36 Besides, high-quality ultrathin 2D FeSe 2 nanosheets have been synthesized by a facile solution method, which further promotes the development of iron chalcogenides.…”