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Ferromagnetism in exfoliated tungsten disulfide nanosheets.

Mao X, Xu Y, Xue Q, Wang W, Gao D - Nanoscale Res Lett (2013)

Bottom Line: Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties.In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF).Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory for Magnetism and Magnetic Materials of MOE, Lanzhou University, Lanzhou 730000, People's Republic of China. gaodq@lzu.edu.cn.

ABSTRACT
Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties. In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF). Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries.

No MeSH data available.


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M-H curves for pristine WS2 bulk and nanosheets and FC and ZFC curves for WS2 nanosheets. (a) The M-H curves for the pristine WS2 bulk and the WS2 nanosheets. (b) M-H curves for the WS2 nanosheets measured at different temperatures, where the diamagnetic signal has been deduced. (c) The FC and ZFC curves for the WS2 nanosheets.
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Figure 4: M-H curves for pristine WS2 bulk and nanosheets and FC and ZFC curves for WS2 nanosheets. (a) The M-H curves for the pristine WS2 bulk and the WS2 nanosheets. (b) M-H curves for the WS2 nanosheets measured at different temperatures, where the diamagnetic signal has been deduced. (c) The FC and ZFC curves for the WS2 nanosheets.

Mentions: Single crystals of the bulk WS2 are expected to be diamagnetic just like any other semiconductors, which is confirmed by the measured magnetization versus magnetic field (M-H) curve shown in Figure 4a using the Quantum Design MPMS magnetometer (Quantum Design, Inc, San Diego, CA, USA) based on superconducting quantum interference device (SQUID). However, for the WS2 nanosheets, even though the magnetic response is dominated by the diamagnetism, it is found that the diamagnetic background is superimposed onto the ferromagnetic loop, implying that the total magnetic susceptibility comprises both diamagnetic and ferromagnetic parts (shown in Figure 4a). After subtracting out the diamagnetic part, the ferromagnetic response at different temperatures has been plotted in Figure 4b. The clear S-shaped saturated open curves at all the measured temperatures with the saturation magnetization (Ms) of 0.002 emu/g at room temperature are observed, revealing the room-temperature ferromagnetism (FM) nature of the WS2 nanosheets. In addition, one can observe that the Ms and the coercivity (Hc) decrease as the temperature increases from 10 to 330 K, revealing a typical signature of nominal FM-like material. The temperature-dependent magnetization measurements for WS2 nanosheets recorded at 100 Oe are shown in Figure 4c. The first measurement was taken after zero-field cooling (ZFC) to the lowest possible temperature (2 K), and in the second run the measurements were taken under field-cooled (FC) conditions. When cooling down from 330 K, both the ZFC and FC data follow similar trend, that is, slow increase of susceptibility until 40 K followed by a sharp rise. Note that the two curves are separated in the whole measured temperature ranges, revealing that the Curie temperature of the sample is expected to exceed 330 K.


Ferromagnetism in exfoliated tungsten disulfide nanosheets.

Mao X, Xu Y, Xue Q, Wang W, Gao D - Nanoscale Res Lett (2013)

M-H curves for pristine WS2 bulk and nanosheets and FC and ZFC curves for WS2 nanosheets. (a) The M-H curves for the pristine WS2 bulk and the WS2 nanosheets. (b) M-H curves for the WS2 nanosheets measured at different temperatures, where the diamagnetic signal has been deduced. (c) The FC and ZFC curves for the WS2 nanosheets.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3818327&req=5

Figure 4: M-H curves for pristine WS2 bulk and nanosheets and FC and ZFC curves for WS2 nanosheets. (a) The M-H curves for the pristine WS2 bulk and the WS2 nanosheets. (b) M-H curves for the WS2 nanosheets measured at different temperatures, where the diamagnetic signal has been deduced. (c) The FC and ZFC curves for the WS2 nanosheets.
Mentions: Single crystals of the bulk WS2 are expected to be diamagnetic just like any other semiconductors, which is confirmed by the measured magnetization versus magnetic field (M-H) curve shown in Figure 4a using the Quantum Design MPMS magnetometer (Quantum Design, Inc, San Diego, CA, USA) based on superconducting quantum interference device (SQUID). However, for the WS2 nanosheets, even though the magnetic response is dominated by the diamagnetism, it is found that the diamagnetic background is superimposed onto the ferromagnetic loop, implying that the total magnetic susceptibility comprises both diamagnetic and ferromagnetic parts (shown in Figure 4a). After subtracting out the diamagnetic part, the ferromagnetic response at different temperatures has been plotted in Figure 4b. The clear S-shaped saturated open curves at all the measured temperatures with the saturation magnetization (Ms) of 0.002 emu/g at room temperature are observed, revealing the room-temperature ferromagnetism (FM) nature of the WS2 nanosheets. In addition, one can observe that the Ms and the coercivity (Hc) decrease as the temperature increases from 10 to 330 K, revealing a typical signature of nominal FM-like material. The temperature-dependent magnetization measurements for WS2 nanosheets recorded at 100 Oe are shown in Figure 4c. The first measurement was taken after zero-field cooling (ZFC) to the lowest possible temperature (2 K), and in the second run the measurements were taken under field-cooled (FC) conditions. When cooling down from 330 K, both the ZFC and FC data follow similar trend, that is, slow increase of susceptibility until 40 K followed by a sharp rise. Note that the two curves are separated in the whole measured temperature ranges, revealing that the Curie temperature of the sample is expected to exceed 330 K.

Bottom Line: Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties.In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF).Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory for Magnetism and Magnetic Materials of MOE, Lanzhou University, Lanzhou 730000, People's Republic of China. gaodq@lzu.edu.cn.

ABSTRACT
Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties. In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF). Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries.

No MeSH data available.


Related in: MedlinePlus