Bousquet Eric, Lelièvre-Berna Eddy, Qureshi Navid, Soh Jian-Rui, Spaldin Nicola A, Urru Andrea, Verbeek Xanthe H, Weber Sophie F
University of Liège, Quartier Agora, Allée du Six Août 19, 4000 Liège 1, Belgium.
Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble, France.
J Phys Condens Matter. 2024 Jan 12;36(15). doi: 10.1088/1361-648X/ad1a59.
We establish the sign of the linear magnetoelectric (ME) coefficient,, in chromia, CrO. CrOis the prototypical linear ME material, in which an electric (magnetic) field induces a linearly proportional magnetization (polarization), and a single magnetic domain can be selected by annealing in combined magnetic () and electric () fields. Opposite antiferromagnetic (AFM) domains have opposite ME responses, and which AFM domain corresponds to which sign of response has previously been unclear. We use density functional theory (DFT) to calculate the magnetic response of a single AFM domain of CrOto an applied in-plane electric field at zero kelvin. We find that the domain with nearest neighbor magnetic moments oriented away from (towards) each other has a negative (positive) in-plane ME coefficient,α⊥, at zero kelvin. We show that this sign is consistent with all other DFT calculations in the literature that specified the domain orientation, independent of the choice of DFT code or functional, the method used to apply the field, and whether the direct (magnetic field) or inverse (electric field) ME response was calculated. Next, we reanalyze our previously published spherical neutron polarimetry data to determine the AFM domain produced by annealing in combinedandfields oriented along the crystallographic symmetry axis at room temperature. We find that the AFM domain with nearest-neighbor magnetic moments oriented away from (towards) each other is produced by annealing in (anti-)parallelandfields, corresponding to a positive (negative) axial ME coefficient,α∥, at room temperature. Sinceα⊥at zero kelvin andα∥at room temperature are known to be of opposite sign, our computational and experimental results are consistent.
我们确定了氧化铬（Cr₂O₃）中线性磁电（ME）系数α的符号。Cr₂O₃是典型的线性磁电材料，其中电场（磁场）会诱导出线性比例的磁化强度（极化强度），并且可以通过在组合磁场（H）和电场（E）中退火来选择单个磁畴。相反的反铁磁（AFM）畴具有相反的磁电响应，而之前尚不清楚哪个AFM畴对应哪种响应符号。我们使用密度泛函理论（DFT）来计算Cr₂O₃的单个AFM畴在零开尔文温度下对施加的面内电场的磁响应。我们发现，最近邻磁矩相互背离（朝向）的畴在零开尔文温度下具有负（正）的面内磁电系数α⊥。我们表明，这个符号与文献中所有指定畴取向的其他DFT计算结果一致，与DFT代码或泛函的选择、施加场的方法以及计算的是直接（磁场）还是逆（电场）磁电响应无关。接下来，我们重新分析我们之前发表的球形中子极化测量数据，以确定在室温下沿晶体对称轴取向的组合H和E场中退火产生的AFM畴。我们发现，最近邻磁矩相互背离（朝向）的AFM畴是由在（反）平行H和E场中退火产生的，对应于室温下正（负）的轴向磁电系数α∥。由于已知零开尔文温度下的α⊥和室温下的α∥符号相反，我们的计算和实验结果是一致的。
