Gorbachev Evgeny A, Alyabyeva Liudmila N, Soshnikov Miroslav V, Lebedev Vasily A, Morozov Anatolii V, Kozlyakova Ekaterina S, Ahmed Asmaa, Eliseev Artem A, Trusov Lev A
Department of Chemistry, Lomonosov Moscow State University, Moscow, 119991, Russia.
Laboratory of Terahertz Spectroscopy, Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Dolgoprudny, 171701, Russia.
Mater Horiz. 2023 Aug 29;10(9):3631-3642. doi: 10.1039/d3mh00626c.
In this study, we demonstrate the sintering of metastable ε-FeO nanoparticles into nanoceramics containing 98 wt% of the epsilon iron oxide phase and with a specific density of 60%. At room temperature, the ceramics retain a giant coercivity of 20 kOe and a sub-terahertz absorption at 190 GHz inherent in the initial nanoparticles. The sintering leads to an increase in the frequencies of the natural ferromagnetic resonance at 200-300 K and larger coercivities at temperatures below 150 K. We propose a simple but working explanation of the low-temperature dynamics of the macroscopic magnetic parameters of the ε-FeO materials the transition of the smallest nanoparticles into a superparamagnetic state. The results are confirmed by the temperature dependence of the magnetocrystalline anisotropy constant and micromagnetic modeling. In addition, based on the Landau-Lifshitz formalism, we discuss features of the spin dynamics in ε-FeO and the possibility of using nanoceramics as sub-terahertz spin-pumping media. Our observations will expand the applicability of ε-FeO materials and promote their integration into telecommunication devices of the next generation.
在本研究中，我们展示了亚稳态ε-FeO纳米颗粒烧结成含有98 wt% ε-氧化铁相且比重为60%的纳米陶瓷。在室温下，该陶瓷保留了初始纳米颗粒固有的20 kOe的巨大矫顽力和190 GHz的亚太赫兹吸收。烧结导致在200 - 300 K时自然铁磁共振频率增加，以及在低于150 K的温度下具有更大的矫顽力。我们对ε-FeO材料宏观磁参数的低温动力学提出了一个简单但有效的解释——最小的纳米颗粒转变为超顺磁状态。结果通过磁晶各向异性常数的温度依赖性和微磁模拟得到证实。此外，基于朗道-里夫希茨形式理论，我们讨论了ε-FeO中自旋动力学的特征以及使用纳米陶瓷作为亚太赫兹自旋泵浦介质的可能性。我们的观察结果将扩大ε-FeO材料的适用性，并促进它们集成到下一代电信设备中。
