Magnetostriction-driven muon localisation in an antiferromagnetic oxide

Magnetostriction drives a rhombohedral distortion in the cubic rock salt antiferromagnet MnO at the Nèel temperature T_N=118 K. As an unexpected consequence we show that this distortion acts to localize the site of an implanted muon due to the accompanying redistribution of electron density. This lifts the degeneracy between equivalent sites, resulting in a single observed muon precession frequency. Above T_N, the muon instead becomes delocalized around a network of equivalent sites. Our first-principles simulations based on Hubbard-corrected density-functional theory and molecular dynamics are consistent with our experimental data and help to resolve a long-standing puzzle regarding muon data on MnO, as well as having wider applicability to other magnetic oxides.

磁致伸缩驱动了立方岩盐反铁磁体MnO在Néel温度T_N=118 K下的正交晶格畸变。令人意外的是，我们揭示了这种畸变由于伴随的电子密度重新分布，导致植入的μ子局域化。这消除了等效位点的简并性，从而产生了单一的观测到的μ子进动频率。在T_N以上，μ子则在整个等效位点网络中发生非局域化。基于修正后的Hubbard密度泛函理论和分子动力学原理的我们首次原理模拟与实验数据一致，有助于解决MnO上μ子数据长期存在的谜团，并具有更广泛的应用于其他磁性氧化物的潜力。