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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.


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(a) χ′ac vs. H of at temperatures 44–55 K and (b) corresponding H vs. T phase diagram for (Cu1−xZnx)2OSeO3 (x = 0.1). The two red circles in (a) corresponding to respective skyrmion zones in (b). Solid and dashed green lines denote the conical phase boundaries.
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f5: (a) χ′ac vs. H of at temperatures 44–55 K and (b) corresponding H vs. T phase diagram for (Cu1−xZnx)2OSeO3 (x = 0.1). The two red circles in (a) corresponding to respective skyrmion zones in (b). Solid and dashed green lines denote the conical phase boundaries.

Mentions: To investigate the influence of Zn doping on the skyrmion phase of Cu2OSeO3, the χ′ac vs. H for (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) are performed for a broad range of T. The representative results of x = 0.1 are shown in the Fig. 5(a). The characteristic features of the χ′ac vs. H curves for x = 0.1 at 51 K ≤ T ≤ 53 K are comparable to that of Cu2OSeO3 at 52 K ≤ T ≤ 56 K (shown in Fig. 4(a)), that the signature of skyrmion phase is noticed with two peaks. With decreasing temperature to 48 K < T < 51 K, the two peaks become smeared. However, as the temperature is lowered to 47 K ≤ T ≤ 48 K, the signature of skyrmion peaks reappeared for H between 80 and 210 Oe. This unexpected observation of second skyrmion phase is a quite novel phenomenon and never been reported in the Cu2OSeO3 system. Along with second skyrmion signature, χ′ac displays second inflection point in the dχ′ac/dH vs. H (see supplementary material) curves. It might indicate the appearance of the second conical boundary in the phase diagram accompanied with the second skyrmion phase. However, further experimental verification needed to confirm these signatures. It is important to emphasize that, similar atomic doping effect in a metallic skyrmion systems such as Mn1−xFexSi and Mn1−xCoxSi31 lead to Quantum phase transitions with a suppressed of helical magnetic and skyrmion phases. Contradictory, the present study indicates the atomic disorder strongly influence the ground state magnetic properties of the Cu2OSeO3 system that lead to more complex magnetic behavior with the generation of additional novel phases in the H-T phase diagram. The multiple inflection points in dχ′ac/dH vs. H curves are systematically changes with the Zn doping concentration in a selected temperature window, which are displayed in the supplementary material. Following the same plotting procedure as mentioned in Fig. 4(b,c), the Fig. 5(b) is successfully constructed from Fig. 5(a).


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) χ′ac vs. H of at temperatures 44–55 K and (b) corresponding H vs. T phase diagram for (Cu1−xZnx)2OSeO3 (x = 0.1). The two red circles in (a) corresponding to respective skyrmion zones in (b). Solid and dashed green lines denote the conical phase boundaries.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: (a) χ′ac vs. H of at temperatures 44–55 K and (b) corresponding H vs. T phase diagram for (Cu1−xZnx)2OSeO3 (x = 0.1). The two red circles in (a) corresponding to respective skyrmion zones in (b). Solid and dashed green lines denote the conical phase boundaries.
Mentions: To investigate the influence of Zn doping on the skyrmion phase of Cu2OSeO3, the χ′ac vs. H for (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) are performed for a broad range of T. The representative results of x = 0.1 are shown in the Fig. 5(a). The characteristic features of the χ′ac vs. H curves for x = 0.1 at 51 K ≤ T ≤ 53 K are comparable to that of Cu2OSeO3 at 52 K ≤ T ≤ 56 K (shown in Fig. 4(a)), that the signature of skyrmion phase is noticed with two peaks. With decreasing temperature to 48 K < T < 51 K, the two peaks become smeared. However, as the temperature is lowered to 47 K ≤ T ≤ 48 K, the signature of skyrmion peaks reappeared for H between 80 and 210 Oe. This unexpected observation of second skyrmion phase is a quite novel phenomenon and never been reported in the Cu2OSeO3 system. Along with second skyrmion signature, χ′ac displays second inflection point in the dχ′ac/dH vs. H (see supplementary material) curves. It might indicate the appearance of the second conical boundary in the phase diagram accompanied with the second skyrmion phase. However, further experimental verification needed to confirm these signatures. It is important to emphasize that, similar atomic doping effect in a metallic skyrmion systems such as Mn1−xFexSi and Mn1−xCoxSi31 lead to Quantum phase transitions with a suppressed of helical magnetic and skyrmion phases. Contradictory, the present study indicates the atomic disorder strongly influence the ground state magnetic properties of the Cu2OSeO3 system that lead to more complex magnetic behavior with the generation of additional novel phases in the H-T phase diagram. The multiple inflection points in dχ′ac/dH vs. H curves are systematically changes with the Zn doping concentration in a selected temperature window, which are displayed in the supplementary material. Following the same plotting procedure as mentioned in Fig. 4(b,c), the Fig. 5(b) is successfully constructed from Fig. 5(a).

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