Aguilera-Del-Toro R H, Torres M B, Aguilera-Granja F, Vega A
Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011 Valladolid, Spain.
Departamento de Matemáticas y Computación, Universidad de Burgos, 09006 Burgos, Spain.
Nanomaterials (Basel). 2020 Sep 11;10(9):1814. doi: 10.3390/nano10091814.
Transition-metal oxide nanoparticles are relevant for many applications in different areas where their superparamagnetic behavior and low blocking temperature are required. However, they have low magnetic moments, which does not favor their being turned into active actuators. Here, we report a systematical study, within the framework of the density functional theory, of the possibility of promoting a high-spin state in small late-transition-metal oxide nanoparticles through alloying. We investigated all possible nanoalloys An-xBxOm (A, B = Fe, Co, Ni; = 2, 3, 4; 0≤x≤n) with different oxidation rates, , up to saturation. We found that the higher the concentration of Fe, the higher the absolute stability of the oxidized nanoalloy, while the higher the Ni content, the less prone to oxidation. We demonstrate that combining the stronger tendency of Co and Ni toward parallel couplings with the larger spin polarization of Fe is particularly beneficial for certain nanoalloys in order to achieve a high total magnetic moment, and its robustness against oxidation. In particular, at high oxidation rates we found that certain FeCo oxidized nanoalloys outperform both their pure counterparts, and that alloying even promotes the reentrance of magnetism in certain cases at a critical oxygen rate, close to saturation, at which the pure oxidized counterparts exhibit quenched magnetic moments.
过渡金属氧化物纳米颗粒在许多不同领域的应用中都具有重要意义，这些应用需要它们具备超顺磁性行为和低阻塞温度。然而，它们的磁矩较低，这不利于将其转变为有源致动器。在此，我们在密度泛函理论的框架内报告了一项系统性研究，该研究旨在探讨通过合金化促进小尺寸晚期过渡金属氧化物纳米颗粒中的高自旋态的可能性。我们研究了所有可能的纳米合金An-xBxOm（A、B = Fe、Co、Ni； = 2、3、4；0≤x≤n），其具有不同的氧化率，直至饱和。我们发现，Fe的浓度越高，氧化纳米合金的绝对稳定性越高，而Ni含量越高，越不易氧化。我们证明，将Co和Ni向平行耦合的较强趋势与Fe较大的自旋极化相结合，对于某些纳米合金实现高总磁矩及其抗氧化稳健性特别有益。特别是，在高氧化率下，我们发现某些FeCo氧化纳米合金的性能优于其纯对应物，并且在某些情况下，合金化甚至会在接近饱和的临界氧速率下促进磁性的再入，而在该临界氧速率下，纯氧化对应物表现出淬灭的磁矩。
