Zorko A, Pregelj M, Gomilšek M, Jagličić Z, Pajić D, Telling M, Arčon I, Mikulska I, Valant M
Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia.
1] Institute of Mathematics, Physics and Mechanics, Jadranska c. 19, SI-1000 Ljubljana, Slovenia [2] Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova c. 2, SI-1000 Ljubljana, Slovenia.
Sci Rep. 2015 Jan 9;5:7703. doi: 10.1038/srep07703.
Diluted magnetic semiconductors possessing intrinsic static magnetism at high temperatures represent a promising class of multifunctional materials with high application potential in spintronics and magneto-optics. In the hexagonal Fe-doped diluted magnetic oxide, 6H-BaTiO3-δ, room-temperature ferromagnetism has been previously reported. Ferromagnetism is broadly accepted as an intrinsic property of this material, despite its unusual dependence on doping concentration and processing conditions. However, the here reported combination of bulk magnetization and complementary in-depth local-probe electron spin resonance and muon spin relaxation measurements, challenges this conjecture. While a ferromagnetic transition occurs around 700 K, it does so only in additionally annealed samples and is accompanied by an extremely small average value of the ordered magnetic moment. Furthermore, several additional magnetic instabilities are detected at lower temperatures. These coincide with electronic instabilities of the Fe-doped 3C-BaTiO3-δ pseudocubic polymorph. Moreover, the distribution of iron dopants with frozen magnetic moments is found to be non-uniform. Our results demonstrate that the intricate static magnetism of the hexagonal phase is not intrinsic, but rather stems from sparse strain-induced pseudocubic regions. We point out the vital role of internal strain in establishing defect ferromagnetism in systems with competing structural phases.
在高温下具有本征静态磁性的稀磁半导体是一类很有前途的多功能材料，在自旋电子学和磁光领域具有很高的应用潜力。在六方铁掺杂稀磁氧化物6H-BaTiO₃-δ中，先前已报道了室温铁磁性。尽管铁磁性对掺杂浓度和加工条件有异常的依赖性，但它被广泛认为是这种材料的固有属性。然而，本文报道的体磁化强度与互补的深度局部探针电子自旋共振和μ子自旋弛豫测量结果的结合，对这一推测提出了挑战。虽然铁磁转变发生在700 K左右，但仅在额外退火的样品中发生，并且伴随着有序磁矩的极小平均值。此外，在较低温度下还检测到了几种额外的磁不稳定性。这些与铁掺杂的3C-BaTiO₃-δ伪立方多晶型的电子不稳定性一致。此外，发现具有冻结磁矩的铁掺杂剂分布不均匀。我们的结果表明，六方相复杂的静态磁性不是固有的，而是源于稀疏的应变诱导伪立方区域。我们指出了内应变在具有竞争结构相的系统中建立缺陷铁磁性方面的关键作用。
