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中国物理学会期刊

二维VOBr2单层的结构畸变及其磁性和铁电性

CSTR: 32037.14.aps.71.20211516

Structural, magnetic and ferroelectric properties of VOBr2 monolayer: A first-principles study

CSTR: 32037.14.aps.71.20211516
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  • 借助第一性原理计算, 对VOBr2单层的结构、磁性以及铁电性进行了系统研究. 计算结果表明低温下VOBr2会产生自发铁电极化, 从高对称顺电相转变为铁电相结构. 与同族姊妹材料VOI2不同的是, V的二聚化现象不仅无法在VOBr2中稳定存在, 还会导致局域磁矩淬灭. 此外, VOBr2易磁化轴在面内a轴方向, 面内a, b轴上近邻磁矩均为反铁磁耦合. VOBr2中的铁电极化主要由V在a轴方向V—O—V链上的铁电位移产生, 大小约为40 μC/cm2. 与铁电同步翻转相比, 通过分步翻转不同链上的铁电极化, 可以有效降低铁电翻转能垒, 从而有望通过低能外场实现部分或个别链上的铁电翻转, 为低能耗高密度铁电存储器件设计提供新的思路和方向.

     

    On the basis of first-principles calculations, the structure, magnetism and ferroelectricity of VOBr2 monolayer are studied systematically in the present work. The calculation results indicate that a spontaneous ferroelectric distortion takes place at low temperature, causing the structure of VOBr2 to transform from a centrosymmetric paraelectric phase to a ferroelectric one. In contrast with its sister compound VOI2, the dimerization of V is unstable in VOBr2 and may quench the local magnetic moment on V ions. Additionally, the easy magnetization axis of VOBr2 monolayer is in-plane along the a-axis, and the magnetic coupling between adjacent local moments is antiferromagnetic both along the a-axis and along the b-axis. Moreover, the ferroelectric displacement of V ions occurs in the a-axis, along the V—O—V chains direction, resulting in a polarization of about 40 μC/cm2. Comparing with the ferro-to-paraelectric reversal pathway, the energy barrier can be effectively reduced for ferroelectric switching on partial or individual V—O—V chains. It is reasonable to believe that the dipole moment flipping on specific chain can be achieved through a moderate external field, thereby providing new direction for designing the low-energy-consumption and high-density ferroelectric memory device.

     

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