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Unusual ferromagnetic critical behavior owing to short-range antiferromagnetic correlations in antiperovskite Cu(1-x)NMn(3+x) (0.1 ≤ x ≤ 0.4).

Lin J, Tong P, Cui D, Yang C, Yang J, Lin S, Wang B, Tong W, Zhang L, Zou Y, Sun Y - Sci Rep (2015)

Bottom Line: In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above T(C).This deviation is gradually smeared as x increases.The short-range antiferromagnetic ordering above T(C) revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China.

ABSTRACT
For ferromagnets, varying from simple metals to strongly correlated oxides,the critical behaviors near the Curie temperature (T(C)) can be grouped into several universal classes. In this paper, we report an unusual critical behavior in manganese nitrides Cu(1-x)NMn(3+x) (0.1 ≤ x ≤ 0.4). Although the critical behavior below T(C) can be well described by mean field (MF) theory, robust critical fluctuations beyond the expectations of any universal classes are observed above T(C) in x = 0.1. The critical fluctuations become weaker when x increases, and the MF-like critical behavior is finally restored at x = 0.4. In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above T(C). This deviation is gradually smeared as x increases. The short-range antiferromagnetic ordering above T(C) revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law.

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Inverse magnetic susceptibility 1/χ(T) for Cu1-xNMn3+x (x = 0.1, 0.2, 0.3 and 0.4).(a) 1/χ(T) at 0.1 kOe for all samples. (b) 1/χ(T) measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe for the x = 0.2 sample. The onset temperatures (T*) where 1/χ(T) deviates from the linear temperature dependence (solid lines) are indicated by the arrows. The ferromagnetic transition for each composition at TC is marked as a solid diamond in (a).
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f1: Inverse magnetic susceptibility 1/χ(T) for Cu1-xNMn3+x (x = 0.1, 0.2, 0.3 and 0.4).(a) 1/χ(T) at 0.1 kOe for all samples. (b) 1/χ(T) measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe for the x = 0.2 sample. The onset temperatures (T*) where 1/χ(T) deviates from the linear temperature dependence (solid lines) are indicated by the arrows. The ferromagnetic transition for each composition at TC is marked as a solid diamond in (a).

Mentions: Figure 1(a) shows 1/χ(T) measured at a magnetic field of 0.1 kOe under the zero-field-cooled mode for Cu1-xNMn3+x with x = 0.1, 0.2, 0.3 and 0.4. The CW law, namely the linear dependence on temperature, holds at temperatures well above TC. As the temperature decreases, the CW behavior breaks down because 1/χ(T) exhibits an upward departure from the linear dependence. The onset temperature of the deviation is denoted as T*. The gap between TC and T* decreases as x increases, that is, the upward deviation in x = 0.4 is less pronounced than in x = 0.1. We note that for the parent sample CuNMn3, no clear deviation from the CW law can be observed in the 1/χ(T) curve31. Figure 1(b) shows a comparison of 1/χ(T)s for x = 0.2 measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe. It is apparent that all the 1/χ(T) curves exhibit an upward departure from the CW behavior. Moreover, T* appears to be insensitive to the applied field. This behavior contradicts the well-known Griffiths phase, in which a downward deviation in 1/χ(T) is usually observed at low magnetic field and disappears at high magnetic field because of the enhanced background PM signal and/or the saturation of the FM components14.


Unusual ferromagnetic critical behavior owing to short-range antiferromagnetic correlations in antiperovskite Cu(1-x)NMn(3+x) (0.1 ≤ x ≤ 0.4).

Lin J, Tong P, Cui D, Yang C, Yang J, Lin S, Wang B, Tong W, Zhang L, Zou Y, Sun Y - Sci Rep (2015)

Inverse magnetic susceptibility 1/χ(T) for Cu1-xNMn3+x (x = 0.1, 0.2, 0.3 and 0.4).(a) 1/χ(T) at 0.1 kOe for all samples. (b) 1/χ(T) measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe for the x = 0.2 sample. The onset temperatures (T*) where 1/χ(T) deviates from the linear temperature dependence (solid lines) are indicated by the arrows. The ferromagnetic transition for each composition at TC is marked as a solid diamond in (a).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300457&req=5

f1: Inverse magnetic susceptibility 1/χ(T) for Cu1-xNMn3+x (x = 0.1, 0.2, 0.3 and 0.4).(a) 1/χ(T) at 0.1 kOe for all samples. (b) 1/χ(T) measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe for the x = 0.2 sample. The onset temperatures (T*) where 1/χ(T) deviates from the linear temperature dependence (solid lines) are indicated by the arrows. The ferromagnetic transition for each composition at TC is marked as a solid diamond in (a).
Mentions: Figure 1(a) shows 1/χ(T) measured at a magnetic field of 0.1 kOe under the zero-field-cooled mode for Cu1-xNMn3+x with x = 0.1, 0.2, 0.3 and 0.4. The CW law, namely the linear dependence on temperature, holds at temperatures well above TC. As the temperature decreases, the CW behavior breaks down because 1/χ(T) exhibits an upward departure from the linear dependence. The onset temperature of the deviation is denoted as T*. The gap between TC and T* decreases as x increases, that is, the upward deviation in x = 0.4 is less pronounced than in x = 0.1. We note that for the parent sample CuNMn3, no clear deviation from the CW law can be observed in the 1/χ(T) curve31. Figure 1(b) shows a comparison of 1/χ(T)s for x = 0.2 measured at 0.1 kOe, 1 kOe, 3 kOe and 10 kOe. It is apparent that all the 1/χ(T) curves exhibit an upward departure from the CW behavior. Moreover, T* appears to be insensitive to the applied field. This behavior contradicts the well-known Griffiths phase, in which a downward deviation in 1/χ(T) is usually observed at low magnetic field and disappears at high magnetic field because of the enhanced background PM signal and/or the saturation of the FM components14.

Bottom Line: In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above T(C).This deviation is gradually smeared as x increases.The short-range antiferromagnetic ordering above T(C) revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China.

ABSTRACT
For ferromagnets, varying from simple metals to strongly correlated oxides,the critical behaviors near the Curie temperature (T(C)) can be grouped into several universal classes. In this paper, we report an unusual critical behavior in manganese nitrides Cu(1-x)NMn(3+x) (0.1 ≤ x ≤ 0.4). Although the critical behavior below T(C) can be well described by mean field (MF) theory, robust critical fluctuations beyond the expectations of any universal classes are observed above T(C) in x = 0.1. The critical fluctuations become weaker when x increases, and the MF-like critical behavior is finally restored at x = 0.4. In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above T(C). This deviation is gradually smeared as x increases. The short-range antiferromagnetic ordering above T(C) revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law.

No MeSH data available.


Related in: MedlinePlus