Abdullahi Yusuf Zuntu, Vatansever Zeynep Demir, Ersan Fatih, Akinci Umit, Akturk Olcay Uzengi, Akturk Ethem
Department of Physics, Aydin Adnan Menderes University, Aydin 09010, Turkey and Department of Physics, Faculty of Science, Kaduna State University, P.M.B. 2339 Kaduna State, Nigeria.
Faculty of Science, Physics Department, Dokuz Eylul University, Tinaztepe Campus, 35390 Izmir, Turkey.
Phys Chem Chem Phys. 2021 Mar 18;23(10):6107-6115. doi: 10.1039/d0cp05802e.
Transition metal boro-carbide (TM2BC) structures crystallize in the layered orthorhombic structure in their bulk phases. In this study, however, we find that TM2BC (TM = Cr, Mn) prefer a tetragonal (t) crystal structure in their monolayer phases due to the occurrence of strong sp2 bonds between the metal and B/C atoms instead of sp3 + sp2 bonds which exist in the orthorhombic phase. The calculated energy difference between the orthorhombic and the tetragonal structures based on density functional theory (DFT) is more than 1 eV per unit cell. In addition, t-Cr2BC and t-Mn2BC monolayers are dynamically and thermally stable with their magnetic metal electronic structures. For further investigations, we combine our DFT calculations with the Monte Carlo simulations and find that both t-TM2BC monolayers show ferromagnetic properties. The calculated Curie temperatures are 846 K and 128 K for t-Cr2BC and t-MnBC sheets, respectively. In addition, we examine the magnetic anisotropy energies (MAE) of t-TM2BC monolayers and find that both structures prefer out-of-plane as the easy axis magnetization direction and the applied electric field can easily modulate the MAE of the monolayers. Our theoretical calculations reveal that t-TM2BC (TM = Cr, Mn) sheets have great potential for the future design of controllable spintronic devices with their tunable MAE properties.
过渡金属硼碳化物（TM2BC）结构在其体相中结晶为层状正交结构。然而，在本研究中，我们发现TM2BC（TM = Cr，Mn）在其单层相中倾向于四方（t）晶体结构，这是由于金属与B/C原子之间存在强sp2键，而非正交相中存在的sp3 + sp2键。基于密度泛函理论（DFT）计算得出的正交结构与四方结构之间的能量差超过每晶胞1 eV。此外，t-Cr2BC和t-Mn2BC单层具有动态和热稳定性，且具有磁性金属电子结构。为了进一步研究，我们将DFT计算与蒙特卡罗模拟相结合，发现两种t-TM2BC单层均表现出铁磁性质。t-Cr2BC和t-MnBC片材的计算居里温度分别为846 K和128 K。此外，我们研究了t-TM2BC单层的磁各向异性能量（MAE），发现两种结构均倾向于将面外方向作为易轴磁化方向，并且施加的电场可以轻松调节单层的MAE。我们的理论计算表明，t-TM2BC（TM = Cr，Mn）片材因其可调的MAE特性，在未来可控自旋电子器件的设计中具有巨大潜力。
