Nature Physics ( IF 19.6 ) Pub Date : 2020-06-22 , DOI: 10.1038/s41567-020-0936-3 Ankit S. Disa , Michael Fechner , Tobia F. Nova , Biaolong Liu , Michael Först , Dharmalingam Prabhakaran , Paolo G. Radaelli , Andrea Cavalleri
Strain engineering is widely used to manipulate the electronic and magnetic properties of complex materials. For example, the piezomagnetic effect provides an attractive route to control magnetism with strain. In this effect, the staggered spin structure of an antiferromagnet is decompensated by breaking the crystal field symmetry, which induces a ferrimagnetic polarization. Piezomagnetism is especially appealing because, unlike magnetostriction, it couples strain and magnetization at linear order, and allows for bi-directional control suitable for memory and spintronics applications. However, its use in functional devices has so far been hindered by the slow speed and large uniaxial strains required. Here we show that the essential features of piezomagnetism can be reproduced with optical phonons alone, which can be driven by light to large amplitudes without changing the volume and hence beyond the elastic limits of the material. We exploit nonlinear, three-phonon mixing to induce the desired crystal field distortions in the antiferromagnet CoF2. Through this effect, we generate a ferrimagnetic moment of 0.2 μB per unit cell, nearly three orders of magnitude larger than achieved with mechanical strain.
中文翻译:
通过晶体场的光学工程使反铁磁体极化
应变工程被广泛用于操纵复杂材料的电子和磁性。例如,压电效应提供了一种有吸引力的途径来控制应变的磁性。在这种效果下,反铁磁体的交错自旋结构通过破坏晶场对称性而被补偿,从而引起亚铁磁极化。压磁特别吸引人,因为它与磁致伸缩不同,它以线性顺序耦合应变和磁化强度,并允许进行适用于存储器和自旋电子学应用的双向控制。然而,迄今为止,其在功能装置中的使用由于所需的慢速和大的单轴应变而受到阻碍。在这里,我们证明了压电磁性的基本特征可以单独用光学声子来再现,可以在不改变体积的情况下通过光将其驱动到大振幅,因此不会超出材料的弹性极限。我们利用非线性三声子混合来在反铁磁体CoF中引起所需的晶体场畸变2。通过这种效果,我们产生0.2的亚铁磁力矩μ乙每单位细胞,近三个数量级比用机械应变来实现较大的。