Abstract
Magnetic anisotropy energy (MAE) is one of the most important properties in two-dimensional magnetism since the magnetization in two dimension is vulnerable to the spin rotational fluctuations. Using density functional theory calculation, we show that perpendicular electric field dramatically enhances the in-plane and out-of-plane magnetic anisotropies in Fe3GeTe2 and Fe4GeTe2 monolayers, respectively, allowing the change of easy axis in both systems. The changes of the MAE under the electric field are understood as the result of charge redistribution inside the layer, which is available due to the three-dimensional (3D) network of Fe atoms in the monolayers. As a result, we suggest that due to the unique structure of FenGeTe2 compounds composed by peculiar 3D networks of metal atoms, the MAE can be dramatically changed by the external perpendicular electric field.
Highlights
Magnetic anisotropy energy (MAE) is one of the most important properties in two-dimensional magnetism since the magnetization in two dimension is vulnerable to the spin rotational fluctuations
Since the magnetic anisotropy energy (MAE) is usually much smaller than the exchange energy, the spin rotational fluctuations are the key ingredients that weakens the magnetic ordering in 2D system, as it is known that the gapless Goldstone mode disables long-range ordering in 2D system according to Mermin–Wagner theorem if the MAE becomes z ero[27,28,29]
Crystal structures of Fe3GeTe2 and Fe4GeTe2 monolayers are shown in Fig. 1a,b, respectively. Both of these materials have the 3D networks of Fe atoms allowing stable itinerant ferromagnetism
Summary
Magnetic anisotropy energy (MAE) is one of the most important properties in two-dimensional magnetism since the magnetization in two dimension is vulnerable to the spin rotational fluctuations. The changes of the MAE under the electric field are understood as the result of charge redistribution inside the layer, which is available due to the three-dimensional (3D) network of Fe atoms in the monolayers. F e3GeTe2 is under the most interests since it is a ferromagnetic metal showing Curie temperature of 220 K at bulk, which is a very high value among the reported vdW m aterials[5, 12,13,14,15,16,17,18,19,20,21,22,23,24]. The Curie temperature in the monolayer is still expected to be lower than that in bulk since the magnetic ordering becomes more sensitive to the thermal fluctuation in two-dimensional (2D) system. As a single unit of the FGT monolayer, the MAE is drastically changed by the external electric field, so we suggest that this system can be applied to the efficient in-situ magnetism control in spintronic devices
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