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Transition from Ferromagnetic Semiconductor to Ferromagnetic Metal with Enhanced Curie Temperature in Cr2Ge2Te6 via Organic Ion Intercalation
journal contribution
posted on 2019-10-18, 14:33 authored by Naizhou Wang, Huaibao Tang, Mengzhu Shi, Hui Zhang, Weizhuang Zhuo, Dayong Liu, Fanbao Meng, Likuan Ma, Jianjun Ying, Liangjian Zou, Zhe Sun, Xianhui ChenMagnetism in the two-dimensional
limit has become an intriguing
topic for exploring new physical phenomena and potential applications.
Especially, the two-dimensional magnetism is often associated with
novel intrinsic spin fluctuations and versatile electronic structures,
which provides vast opportunities in 2D material research. However,
it is still challenging to verify candidate materials hosting two-dimensional
magnetism, since the prototype systems have to be realized by using
mechanical exfoliation or atomic layer deposition. Here, an alternative
manipulation of two-dimensional magnetic properties via electrochemical
intercalation of organic molecules is reported. Using tetrabutyl ammonium
(TBA+), we synthesized a (TBA)Cr2Ge2Te6 hybrid superlattice with metallic behavior, and the
Curie temperature is significantly increased from 67 K in pristine
Cr2Ge2Te6 to 208 K in (TBA)Cr2Ge2Te6. Moreover, the magnetic easy
axis changes from the ⟨001⟩ direction in Cr2Ge2Te6 to the ab-plane in
(TBA)Cr2Ge2Te6. Theoretical calculations
indicate that the drastic increase of the Curie temperature can be
attributed to the change of magnetic coupling from a weak superexchange
interaction in pristine Cr2Ge2Te6 to a strong double-exchange interaction in (TBA)Cr2Ge2Te6. These findings are the first demonstration
of manipulation of magnetism in magnetic van der Waals materials by
means of intercalating organic ions, which can serve as a convenient
and efficient approach to explore versatile magnetic and electronic
properties in van der Waals crystals.