Friák Martin, Mazalová Martina, Turek Ilja, Zemanová Adéla, Kaštil Jiří, Kamarád Jiří, Míšek Martin, Arnold Zdeněk, Schneeweiss Oldřich, Všianská Monika, Zelený Martin, Kroupa Aleš, Pavlů Jana, Šob Mojmír
Institute of Physics of Materials, v.v.i., Czech Academy of Sciences, Žižkova 22, CZ-616 62 Brno, Czech Republic.
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic.
Materials (Basel). 2021 Jan 22;14(3):523. doi: 10.3390/ma14030523.
We have performed a quantum-mechanical study of a series of stoichiometric Ni2MnSn structures focusing on pressure-induced changes in their magnetic properties. Motivated by the facts that (i) our calculations give the total magnetic moment of the defect-free stoichiometric Ni2MnSn higher than our experimental value by 12.8% and (ii) the magnetic state is predicted to be more sensitive to hydrostatic pressures than seen in our measurements, our study focused on the role of point defects, in particular Mn-Ni, Mn-Sn and Ni-Sn swaps in the stoichiometric Ni2MnSn. For most defect types we also compared states with both ferromagnetic (FM) and anti-ferromagnetic (AFM) coupling between (i) the swapped Mn atoms and (ii) those on the Mn sublattice. Our calculations show that the swapped Mn atoms can lead to magnetic moments nearly twice smaller than those in the defect-free Ni2MnSn. Further, the defect-containing states exhibit pressure-induced changes up to three times larger but also smaller than those in the defect-free Ni2MnSn. Importantly, we find both qualitative and quantitative differences in the pressure-induced changes of magnetic moments of individual atoms even for the same global magnetic state. Lastly, despite of the fact that the FM-coupled and AFM-coupled states have often very similar formation energies (the differences only amount to a few meV per atom), their structural and magnetic properties can be very different.
我们对一系列化学计量比的Ni2MnSn结构进行了量子力学研究，重点关注压力引起的磁性能变化。基于以下事实：（i）我们的计算得出无缺陷化学计量比的Ni2MnSn的总磁矩比我们的实验值高12.8%；（ii）预测磁态对静水压力比我们测量中看到的更敏感，我们的研究聚焦于点缺陷的作用，特别是化学计量比的Ni2MnSn中Mn-Ni、Mn-Sn和Ni-Sn的交换。对于大多数缺陷类型，我们还比较了（i）交换的Mn原子之间以及（ii）Mn子晶格上的原子之间具有铁磁（FM）和反铁磁（AFM）耦合的状态。我们的计算表明，交换的Mn原子导致的磁矩比无缺陷的Ni2MnSn中的磁矩小近两倍。此外，含缺陷状态的压力诱导变化比无缺陷的Ni2MnSn中的变化大至三倍，但也有小的情况。重要的是，即使对于相同的全局磁态，我们发现单个原子磁矩的压力诱导变化在定性和定量上都存在差异。最后，尽管FM耦合态和AFM耦合态通常具有非常相似的形成能（差异仅为每个原子几meV），但它们的结构和磁性能可能非常不同。
