Surface oxidation in a van der Waals ferromagnet Fe3-xGeTe2

다국어 초록 (Multilingual Abstract)

We investigate the surface oxidation in a van der Waals ferromagnet Fe3-xGeTe2, a material widely utilized for spintronic applications. While known for its relative air-insensitivity, exposure to air during the handling process (e.g. device or heterostructure fabrication) can lead to reduction or disappearance of its magnetic signal.
Comparison of x-ray absorption and x-ray magnetic circular dichroism spectra between pristine and air-exposed Fe3-xGeTe2 confirm a naturally oxidized surface layer on the material. The surface oxide layer has predominantly Fe3+ content. X-ray absorption spectroscopy done on micron-sized exfoliated Fe3-xGeTe2 flakes reveal that the change in the surface chemical properties can be quite significant for thin flakes. The surface modulation of Fe3- xGeTe2 can lead to inaccuracies in characterizing its interfacial magnetic and spin transport properties, and complicate device and heterostructure fabrication processes.

참고문헌 (Reference)

1 J. P. Crocombette, "X-rayabsorption spectroscopy at the Fe L2,3 threshold in iron oxides" 52 : 3143-3150, 1995

2 송경미, "X-ray scattering study on the electric field-induced interfacial magnetic anisotropy modulation at CoFeB / MgO interfaces" 한국물리학회 18 (18): 1212-1217, 2018

3 F. Jim´enez-Villacorta, "X-ray magnetic circular dichroism study of the blocking process in nanostructured ironiron oxide core-shell systems" 84 : 172404-, 2011

4 Z. Wang, "Very large tunneling magnetoresistance in layered magnetic semiconductor CrI3" 9 : 2516-, 2018

5 A. K. Geim, "Van der Waals heterostructures" 499 : 419-425, 2013

6 C. Gong, "Two-dimensional magnetic crystals and emergent heterostructure devices" 363 : eaav4450-, 2019

7 Z. Wang, "Tunneling spin valves based on Fe3GeTe2/hBN/Fe3GeTe2 van der Waals heterostructures" 18 : 4303-4308, 2018

8 K. V. Shanavas, "Theoretical model for Rashba spin-orbit interaction in d electrons" 90 : 165108-, 2014

9 P. S. Miedema, "The iron L edges: Fe 2p X-ray absorption and electron energy loss spectroscopy" 187 : 32-48, 2013

10 Cheng-Tai Kuo, "The energy band alignment at the interface between mechanically exfoliated few-layer NiPS3 nanosheets and ZnO" 한국물리학회 16 (16): 404-408, 2016

11 K. Binder, "Surface effects on magnetic phase transitions" 9 : 2194-2214, 1974

12 D. L. Mills, "Surface effects in magnetic crystals near the ordering temperature" 3 : 3887-3895, 1971

13 G. H. Vurens, "Structure, composition and chemisorption studies of thin ordered iron oxide films on platinum (111)" 201 : 129-144, 1988

14 J. Vogel, "Structure and magnetism of Pd in Pd/Fe multilayers studied by x-ray magnetic circular dichroism at the Pd L2,3 edges" 55 : 3663-3669, 1997

15 Y. A. Bychkov, "Properties of a 2D electron gas with lifted spectral degeneracy" 39 : 78-81, 1984

16 H. H. Kim, "One million percent tunnel magnetoresistance in a magnetic van der Waals heterostructure" 18 : 4885-4890, 2018

17 T.-E. Park, "N´eel-type skyrmions and their current-induced motion in van der Waals ferromagnet-based heterostructures"

18 J. Stohr, "NEXAFS Spectroscopy" Springer-Verlag 1992

19 J. B. Kortright, "Magnetization imaging using scanning transmission x-ray microscopy" 507 : 49-54, 2000

20 Jiho Kim, "Long-term stability study of graphene-passivated black phosphorus under air exposure" 한국물리학회 16 (16): 165-169, 2016

21 B. Huang, "Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit" 546 : 270-273, 2017

22 K. Kim, "Large anomalous Hall current induced by topological nodal lines in a ferromagnetic van der Waals semimetal" 17 : 794-799, 2018

23 R. Zboril, "Iron(III) oxides from thermal processes synthesis, structural and magnetic properties, mossbauer ¨ spectroscopy characterization, and applications" 14 : 969-982, 2002

24 F. Hellman, "Interface-induced phenomena in magnetism" 89 : 025006-, 2017

25 F. Genuzio, "Interconversion of α-Fe2O3 and Fe3O4 thin films: mechanisms, morphology, and evidence for unexpected substrate participation" 118 : 29068-29076, 2014

26 C. Tan, "Hard magnetic properties in nanoflake van der Waals Fe3GeTe2" 9 : 1554-, 2018

27 "Handbook of Solid State Chemistry, vol. 2" Wiley-VCH Verlag GmbH & Co 2017

28 G. Zheng, "Gate-tuned interlayer coupling in van der Waals ferromagnet Fe3GeTe2 nanoflakes" 125 : 047202-, 2020

29 Y. Deng, "Gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2" 563 : 94-99, 2018

30 H. -J. Deiseroth, "Fe3GeTe2 and Ni3GeTe2 – two new layered transition-metal compounds: crystal structures, HRTEM investigations, and magnetic and electrical properties" 2006 : 1561-1567, 2006

31 J. Stohr, "Exploring the microscopic origin of magnetic anisotropies with X-ray magnetic circular dichroism(XMCD)spectroscopy" 200 : 470-497, 1999

32 C. T. Chen, "Experimental confirmation of the X-ray magnetic circular dichroism sum rules for iron and cobalt" 75 : 152-155, 1995

33 H. K. Gweon, "Exchange bias in weakly interlayer-coupled van der Waals magnet Fe3GeTe2" 21 : 1672-1678, 2021

34 L. Berger, "Emission of spin waves by a magnetic multilayer traversed by a current" 54 : 9353-9358, 1996

35 J. -X. Zhu, "Electronic correlation and magnetism in the ferromagnetic metal Fe3GeTe2" 93 : 144404-, 2016

36 R. Nakajima, "Electron-yield saturation effects in L-edge x-ray magnetic circular dichroism spectra of Fe, Co, and Ni" 59 : 6421-6429, 1999

37 K. Ando, "Electric manipulation of spin relaxation using the spin Hall effect" 101 : 036601-, 2008

38 C. Gong, "Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals" 546 : 265-269, 2017

39 L. Liu, "Current-induced switching of perpendicularly magnetized magnetic layers using spin torque from the spin Hall effect" 109 : 096602-, 2012

40 J. C. Slonczewski, "Current-driven excitation of magnetic multilayers" 159 : L1-L7, 1996

41 K. Binder, "Critical phenomena at surfaces" 163 : 17-30, 1990

42 Y. Liu, "Critical behavior of the van der Waals bonded ferromagnet Fe3-xGeTe2" 96 : 144429-, 2017

43 S. Y. Park, "Controlling the magnetic anisotropy of the van der Waals ferromagnet Fe3GeTe2 through hole doping" 20 : 95-100, 2020

44 D. -O. Kim, "Asymmetric magnetic proximity effect in a Pd/Co/Pd trilayer system" 6 : 25391-, 2016

45 D. Kim, "Antiferromagnetic coupling of van der Waals ferromagnetic Fe3GeTe2" 30 : 245701-, 2019

46 Y. Liu, "Anomalous Hall effect in the van der Waals bonded ferromagnet Fe3-xGeTe2" 97 : 165415-, 2018