[seminar] Reminder for seminar tomorrow Christian Teichert @CEMS - joint IRB & IoP seminar, Thursday 7th July 2022 at 11:00, IRB 3rd wing, lecture hall

[Damir Dominko]

CEMS seminar - joint IRB & IoP seminar,Thursday 7th July 2022 at 11:00, 
IRB 3rd wing, lecture hall **

*Two-dimensional magnetism in layered minerals*
*Christian Teichert*
*Institut für Physik, Montanuniversität Leoben, A-8700 Leoben, Austria
teichert at unileoben.ac.at
*

Since the first reports on intrinsically magnetic two-dimensional (2D) 
materials in 2017 [1,2], the price-to-pay for accessing their monolayers 
is still the lack of ambient stability.
We discovered in a mineral aggregate – mainly composed of hematite, 
magnetite, and chalcopyrite – soft layers of which macroscopic flakes 
easily could be peeled off that stuck to a permanent magnet. Employing 
mechanical exfoliation, we succeeded in thinning and transferring 
micrometer sized – mainly hexagonally shaped – flakes to SiO2 
substrates. Energy dispersive x-ray spectroscopy (EDS) revealed 
magnesium and silica as major components of the flakes. Raman 
spectroscopy indicated the presence of hydroxide groups, pointing 
towards talc, a hydrated magnesium phyllosilicate mineral, namely talc 
(Mg3Si4O10(OH)2). Long-term EDS and Raman spectroscopy revealed that in 
the flakes about 10 % of the Mg atoms are substituted by Fe which 
clusters into about 20 nm regions according to scanning transmission 
electron microscopy (STEM). With atomic force microscopy, a minimum 
flake thickness of 1 nm was determined indicating cleavage down to a 
talc monolayer. Combined magnetic force microscopy (MFM) measurements in 
external out-of-plane fields up to 0.5 T and SQUID magnetometry 
measurements imply that the 2D Fe-rich talc exhibits weak ferromagnetic 
behavior. The flakes are also showing long-term stability under ambient 
conditions in contrast to the 2D magnets reported so far [3]. In an 
outlook, it will be demonstrated that also other iron rich 
phyllosilicates can serve as a platform for 2D magnetism.

[1] C. Gong, et al., Nature 546, 265 (2017).
[2] B. Huang, et al., Nature 546, 270 (2017).
[3] A. Matković, et al., npj 2D Mat. Appl. 5, 94 (2021).

Work is supported by FWF, Austria via 2020 START program (grant # Y1298 
N) and  has been performed in collaboration with A. Matković, M. Z. 
Khan, K.-P. Gradwohl, M. Kratzer O. E. Peil, C. Gammer, R. Bakker, J. 
Raith (all Leoben), E. Fisslthaler, D. Knez, F. Hofer (all Graz), and A. 
Sharma, D.R.T. Zahn, G. Salvan (all Chemnitz).


*Seminar**hosts**: Neven Šantić <mailto:nsantic at ifs.hr> i Damir Dominko 
<mailto:ddominko at ifs.hr>*
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