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At present, the research on two-dimensional (2D) ferromagnets is mainly concentrated on van der Waals materials, while the successful preparation of strain-free freestanding 2D perovskite films provides a great opportunity for designing 2D ferromagnets beyond van der Waals materials. Perovskite oxide SrRuO3, a typical perovskite itinerant ferromagnet, has broad application prospects in many fields. In this work, the lattice dynamics, ground-state structure, electronic and magnetic properties of its perovskite monolayer with formula Sr2RuO4, as well as the effect of external electric field, are studied by combining first-principles calculation, symmetry analysis and Monte Carlo simulation. The influence of the Hubbard parameter U is also revealed. The results indicate that the ground-state structure under all U values presents the structural phase (space group P4/mbm) generated by octahedral rotation distortion. Similar to the SrRuO3 bulk, Sr2RuO4 has a monolayer ground-state phase that exhibits ferromagnetism, which is independent of the U value and thus robust. Density functional theory calculation using Hubbard parameter U predicts the ground-state phase of the monolayer to be a ferromagnetic half metal with an out-of-plane easy-magnetization axis, while excluding that the U parameter predicts the ground-state phase to be a ferromagnetic metallic state. The ferromagnetism mainly originates from the strong ferromagnetic exchange interaction between the nearest neighbor spin pairs. The simulated Curie temperature of the Sr2RuO4 monolayer is 177 K, which is close to the value (150 K) of its bulk phase. The out-of-plane electric field does not change the ground-state structure nor ferromagnetism of the Sr2RuO4 monolayer, but can significantly modulate its electronic property and magnetic property. When an external electric field exceeding 0.3 V/Å is applied, the system undergoes a transition from a ferromagnetic half-metal state to a ferromagnetic metallic state. This work indicates the potential application of Sr2RuO4 monolayer in low-dimensional spintrnic devices, and provides a reference for developing perovskite-based 2D ferromagnets and realizing the control of 2D magnetism by electric field.
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Keywords:
- two-dimensional ferromagnetism /
- perovskite /
- first principles
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] -
Distortion modes Space group $ \Delta E $/(meV·f.u.–1) $ U_{{\mathrm{eff}}} = 0 $ $ U_{{\mathrm{eff}}} = 0.5 $ $ U_{{\mathrm{eff}}} = 1.2 $ $ U_{{\mathrm{eff}}} = 1.5 $ $ U_{{\mathrm{eff}}} = 2 $ $ {\mathrm{Para}} $ $ P4/mmm $ 154 172 225 227 214 ${\mathrm{ R}}(M_2^+) $ $ P4/mbm $ 0 0 0 0 0 $ {\mathrm{T}}(a, 0)(M_5^+) $ $ Pmna $ — — 228 225 214 $ {\mathrm{T}}(a, a)(M_5^+) $ $ Cmma $ — — 227 224 212 $ {\mathrm{JT}}_1(M_3^+) $ $ P4/mbm $ — — — — — $ {\mathrm{JT}}_2(M_4^+) $ $ P4/mmm $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{JT}}_1 $ $ Pbam $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{JT_2}} $ $ P4/m $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{T}}(a, 0) $ $ P2_1/c $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{T}}(a, a) $ $ C2/m $ — — — — — $ {\mathrm{T}}(a, 0) \oplus {\mathrm{JT}}_1 $ $ P2_1/c $ — — — — — $ {\mathrm{T}}(a, 0) \oplus {\mathrm{JT_2}} $ $ P2/m $ — — — — — $ {\mathrm{T}}(a, a) \oplus{\mathrm{ JT}}_1 $ $ C2/m $ — — — — — $ {\mathrm{T}}(a, a) \oplus {\mathrm{JT}}_2 $ $ C2/m $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{T}}(a, 0) \oplus {\mathrm{JT}}_1 $ $ P2_1/c $ — — — — — ${\mathrm{ R}} \oplus {\mathrm{T}}(a, 0) \oplus {\mathrm{JT}}_2 $ $ P\bar{1} $ — — — — — $ {\mathrm{R}} \oplus{\mathrm{ T}}(a, a) \oplus {\mathrm{JT}}_1 $ $ P\bar{1} $ — — — — — $ {\mathrm{R}} \oplus {\mathrm{T}}(a, a) \oplus {\mathrm{JT}}_2 $ $ P\bar{1} $ — — — — — 
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$ U_{{\mathrm{eff}}} $/eV $ J_1 $/meV $ J_2 $/meV K/meV M/$ \mu_{\mathrm{B}} $ $ T_{\mathrm{C}} $/K 0 11.48 –1.35 1.57 0.73 81 0.5 15.39 1.73 1.11 0.96 111 1.2 25.34 –2.41 1.83 1.43 177 1.5 31.18 –3.90 1.70 1.44 195 2 38.38 –8.53 1.81 1.47 202
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[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38]
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