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Unexpected observation of splitting of skyrmion phase in Zn doped Cu2OSeO3.

Wu HC, Wei TY, Chandrasekhar KD, Chen TY, Berger H, Yang HD - Sci Rep (2015)

Bottom Line: The effect of Zn doping upon saturation magnetization (MS) indicates that the Zn favors to occupying Cu(II) square pyramidal crystallographic site.The Zn doping concentration is found to affect greatly the M-T and χ'ac-T.H curves.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Sun Yat-Sen University, Kaohsiung, 804 Taiwan.

ABSTRACT
Polycrystalline (Cu1-xZnx)2OSeO3 (0≤x≤0.2) samples were synthesized using solid-state reaction and characterized by X-ray diffraction (XRD). The effect of Zn doping upon saturation magnetization (MS) indicates that the Zn favors to occupying Cu(II) square pyramidal crystallographic site. The AC susceptibility (χ'ac) was measured at various temperatures (χ'ac-T) and magnetic field strengths (χ'ac-H). The Zn doping concentration is found to affect greatly the M-T and χ'ac-T. The skyrmion phase has been inferred from the χ'ac-H data, and then indicated within the H-T phase diagrams for various Zn doping concentrations. The striking and unexpected observation is that the skyrmion phase region becomes split upon Zn doping concentration. Interestingly, second conical boundary accompanied by second skyrmion phase was also observed from dχ'ac/dH vs. H curves. Atomic site disorder created by the chemical doping modulates the delicate magnetic interactions via change in the Dzyaloshinskii-Moriya (DM) vector of distorted Cu(II) square pyramidal, thereby splitting of skyrmion phase might occur. These findings illustrate the potential of using chemical and atomic modification for tuning the temperature and field dependence of skyrmion phase of Cu2OSeO3.

No MeSH data available.


Related in: MedlinePlus

(a) M vs. H curves of (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) series at T = 5 K; Inset shows the MS vs. Zn doping concentration. Dashed lines indicate the theoretically predicted occupation probabilities of Zn at (Cu(I) or Cu(II) crystallographic positions respectively. The experimental data matches the Cu(II) site occupation. (b) The graphical representation of resultant magnetic moment for (I) Cu2OSeO3 (II) Zn at Cu(I) site and (III) Zn at Cu(II) site respectively.
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f2: (a) M vs. H curves of (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) series at T = 5 K; Inset shows the MS vs. Zn doping concentration. Dashed lines indicate the theoretically predicted occupation probabilities of Zn at (Cu(I) or Cu(II) crystallographic positions respectively. The experimental data matches the Cu(II) site occupation. (b) The graphical representation of resultant magnetic moment for (I) Cu2OSeO3 (II) Zn at Cu(I) site and (III) Zn at Cu(II) site respectively.

Mentions: Figure 2 depicts the isothermal M-H loops at T = 5 K with the field up to 5 T for (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2). The saturation magnetization MS at 5 T is observed to be 0.519 μB/Cu2+ for x = 0, a close match with the theoretical predicted (0.5 μB/Cu2+) ferrimagnetic alignment of Cu spins9. For the doping case, the nonmagnetic Zn2+ ion might occupy two possible crystallographic (Cu(I)/Cu(II)) sites. If non-magnetic Zn replaces any one of three ferromagnetically aligned Cu(II) sites that decrease the overall magnetization of the unit cell (0.25 μB/Cu2+). On the other hand, Zn placed at Cu(I) site enhances the overall magnetization as well as ferromagnetic strength (0.75 μB/Cu2+). To estimate the probable Zn site occupation we have simulated the MS values for both the case of Cu(I)/Cu(II)) sites. The inset also plots the theoretically predicted values that would be expected for each of doping sites. The measured values line up well with theoretical expectation for the Cu(II) sites, which reveals that the nonmagnetic Zn2+ ions favor occupying the Cu(II) site.


Unexpected observation of splitting of skyrmion phase in Zn doped Cu2OSeO3.

Wu HC, Wei TY, Chandrasekhar KD, Chen TY, Berger H, Yang HD - Sci Rep (2015)

(a) M vs. H curves of (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) series at T = 5 K; Inset shows the MS vs. Zn doping concentration. Dashed lines indicate the theoretically predicted occupation probabilities of Zn at (Cu(I) or Cu(II) crystallographic positions respectively. The experimental data matches the Cu(II) site occupation. (b) The graphical representation of resultant magnetic moment for (I) Cu2OSeO3 (II) Zn at Cu(I) site and (III) Zn at Cu(II) site respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4563258&req=5

f2: (a) M vs. H curves of (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) series at T = 5 K; Inset shows the MS vs. Zn doping concentration. Dashed lines indicate the theoretically predicted occupation probabilities of Zn at (Cu(I) or Cu(II) crystallographic positions respectively. The experimental data matches the Cu(II) site occupation. (b) The graphical representation of resultant magnetic moment for (I) Cu2OSeO3 (II) Zn at Cu(I) site and (III) Zn at Cu(II) site respectively.
Mentions: Figure 2 depicts the isothermal M-H loops at T = 5 K with the field up to 5 T for (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2). The saturation magnetization MS at 5 T is observed to be 0.519 μB/Cu2+ for x = 0, a close match with the theoretical predicted (0.5 μB/Cu2+) ferrimagnetic alignment of Cu spins9. For the doping case, the nonmagnetic Zn2+ ion might occupy two possible crystallographic (Cu(I)/Cu(II)) sites. If non-magnetic Zn replaces any one of three ferromagnetically aligned Cu(II) sites that decrease the overall magnetization of the unit cell (0.25 μB/Cu2+). On the other hand, Zn placed at Cu(I) site enhances the overall magnetization as well as ferromagnetic strength (0.75 μB/Cu2+). To estimate the probable Zn site occupation we have simulated the MS values for both the case of Cu(I)/Cu(II)) sites. The inset also plots the theoretically predicted values that would be expected for each of doping sites. The measured values line up well with theoretical expectation for the Cu(II) sites, which reveals that the nonmagnetic Zn2+ ions favor occupying the Cu(II) site.

Bottom Line: The effect of Zn doping upon saturation magnetization (MS) indicates that the Zn favors to occupying Cu(II) square pyramidal crystallographic site.The Zn doping concentration is found to affect greatly the M-T and χ'ac-T.H curves.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Sun Yat-Sen University, Kaohsiung, 804 Taiwan.

ABSTRACT
Polycrystalline (Cu1-xZnx)2OSeO3 (0≤x≤0.2) samples were synthesized using solid-state reaction and characterized by X-ray diffraction (XRD). The effect of Zn doping upon saturation magnetization (MS) indicates that the Zn favors to occupying Cu(II) square pyramidal crystallographic site. The AC susceptibility (χ'ac) was measured at various temperatures (χ'ac-T) and magnetic field strengths (χ'ac-H). The Zn doping concentration is found to affect greatly the M-T and χ'ac-T. The skyrmion phase has been inferred from the χ'ac-H data, and then indicated within the H-T phase diagrams for various Zn doping concentrations. The striking and unexpected observation is that the skyrmion phase region becomes split upon Zn doping concentration. Interestingly, second conical boundary accompanied by second skyrmion phase was also observed from dχ'ac/dH vs. H curves. Atomic site disorder created by the chemical doping modulates the delicate magnetic interactions via change in the Dzyaloshinskii-Moriya (DM) vector of distorted Cu(II) square pyramidal, thereby splitting of skyrmion phase might occur. These findings illustrate the potential of using chemical and atomic modification for tuning the temperature and field dependence of skyrmion phase of Cu2OSeO3.

No MeSH data available.


Related in: MedlinePlus