Browsing by Author "Deng, JX"

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    Neutron diffraction study of unusual magnetic behaviors in the Ho2Fe11Al6 intermetallic compound
    (American Chemical Society, 2019-09-30) Cao, Y; Lin, K; Liu, ZN; Hu, JY; Wang, CW; Avdeev, M; Li, Q; Deng, JX; Chen, J; Zhang, HJ; Xing, XR
    Knowledge of structure–property relationships is fundamental but significant in the exploitation of magnetic materials. Here we report that the high Al substitution for Fe transformed the crystal structure from a hexagonal Ho2Fe17 compound to a rhombohedral Ho2Fe11Al6 compound. Intriguingly, the latter shows unusual evolution of magnetization around 86 and 220 K compared with the former. Integrated investigations of the detailed structure analysis and magnetic performance on the Ho2Fe11Al6 compound demonstrate that the Ho2Fe11Al6 compound possesses a stable rhombohedral structure (R3̅m) from 5 to 430 K with preferred occupation of Al atoms and ferrimagnetic structure in which the magnetic moments of Ho and Fe lie antiparallel in the basal plane below the Curie temperature. The results of the temperature dependence of moments reveal that the disparate rates of change of the moments for Ho and Fe sublattices give rise to unusual evolution of magnetization around 86 and 220 K and then turn to paramagnetic above 280 K. This work provides clear structure and magnetization information on the Ho2Fe11Al6 compound, which may be beneficial to guiding the future development of magnetic materials. © 2019 American Chemical Society
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    Pressure-modulated magnetism and negative thermal expansion in the Ho2Fe17 intermetallic compound
    (American Chemical Society, 2023-05-25) Cao, YL; Zhou, H; Khmelevskyi, S; Lin, K; Avdeev, M; Wang, CW; Wang, B; Hu, F; Kato,; Hattori, T; Abe, J; Ohara, K; Kawaguchi, S; Li, Q; Fukuda, M; Nishikubo, T; Lee, K; Koike, T; Liu, Q; Miao, J; Deng, JX; Shen, B; Azuma, M; Xing, X
    Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in Ho2Fe17 on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level (EF), which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials. © 2024 American Chemical Society
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    Ultrawide temperature range super-invar behavior of R2(Fe, Co)17 materials (R = rare earth)
    (American Physical Society, 2021-07-30) Cao, YL; Lin, KM; Khmelevskyi, S; Avdeev, M; Taddei, KM; Zhang, Q; Huang, QZ; Li, Q; Kato, K; Tang, CC; Gibbs, A; Wang, CW; Deng, JX; Chen, J; Zhang, HJ; Xing, XR
    Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R2(Fe,Co)17 materials (R=rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3–461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve “ultrawide” SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials. © 2021 American Physical Society