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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.

No MeSH data available.


Related in: MedlinePlus

ESR spectra, dP/dH, as a function of temperature for Cu1-xNMn3+x.(a) dP/dH for x = 0.1. (b) dP/dH for x = 0.3. Note that the spectra plotted here were normalized and shifted (see the text for details). The dashed lines indicate the evolutions of resonant peaks (P1 and P2) with temperature above TC.
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f3: ESR spectra, dP/dH, as a function of temperature for Cu1-xNMn3+x.(a) dP/dH for x = 0.1. (b) dP/dH for x = 0.3. Note that the spectra plotted here were normalized and shifted (see the text for details). The dashed lines indicate the evolutions of resonant peaks (P1 and P2) with temperature above TC.

Mentions: ESR has been demonstrated to be an effective tool to probe the local and microscopic magnetic states of materials. To elucidate the nature of the critical behavior around TC, temperature-dependent derivative ESR spectra (dP/dH) were measured for x = 0.1 and x = 0.3 samples and are presented in Figure 3(a) and (b), respectively. Here, the dP/dH data were normalized to the positive peak value and then shifted accordingly such that the evolution of the line shape could be easily seen. As shown in Figure 3(a) for x = 0.1, the dP/dH spectrum is asymmetrically distorted below TC. When approaching TC, the dP/dH spectrum makes a small shift toward higher fields and becomes less asymmetrical. Once above TC, however, the spectrum broadens and distorts again with increasing temperature. Synchronously, a shoulder-like feature appears on the right side of the original peak and finally evolves into a sharp peak above 235 K. Above this temperature, the two resonant peaks are clearly distinguishable in the dP/dH spectra with very different peak widths. Hereafter, the original peak is denoted as P1, whereas the new peak is denoted as P2. As shown in Figure 3(a), P1 keeps broadening as the temperature is further increased and eventually becomes invisible above 350 K, where only P2 is left. As displayed in Figure 3(b), the ESR spectra for x = 0.3 recorded with a bigger temperature interval than for x = 0.1 show a similar evolution with temperature, even though the wide peak (P1) still exists at 400 K.


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)

ESR spectra, dP/dH, as a function of temperature for Cu1-xNMn3+x.(a) dP/dH for x = 0.1. (b) dP/dH for x = 0.3. Note that the spectra plotted here were normalized and shifted (see the text for details). The dashed lines indicate the evolutions of resonant peaks (P1 and P2) with temperature above TC.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: ESR spectra, dP/dH, as a function of temperature for Cu1-xNMn3+x.(a) dP/dH for x = 0.1. (b) dP/dH for x = 0.3. Note that the spectra plotted here were normalized and shifted (see the text for details). The dashed lines indicate the evolutions of resonant peaks (P1 and P2) with temperature above TC.
Mentions: ESR has been demonstrated to be an effective tool to probe the local and microscopic magnetic states of materials. To elucidate the nature of the critical behavior around TC, temperature-dependent derivative ESR spectra (dP/dH) were measured for x = 0.1 and x = 0.3 samples and are presented in Figure 3(a) and (b), respectively. Here, the dP/dH data were normalized to the positive peak value and then shifted accordingly such that the evolution of the line shape could be easily seen. As shown in Figure 3(a) for x = 0.1, the dP/dH spectrum is asymmetrically distorted below TC. When approaching TC, the dP/dH spectrum makes a small shift toward higher fields and becomes less asymmetrical. Once above TC, however, the spectrum broadens and distorts again with increasing temperature. Synchronously, a shoulder-like feature appears on the right side of the original peak and finally evolves into a sharp peak above 235 K. Above this temperature, the two resonant peaks are clearly distinguishable in the dP/dH spectra with very different peak widths. Hereafter, the original peak is denoted as P1, whereas the new peak is denoted as P2. As shown in Figure 3(a), P1 keeps broadening as the temperature is further increased and eventually becomes invisible above 350 K, where only P2 is left. As displayed in Figure 3(b), the ESR spectra for x = 0.3 recorded with a bigger temperature interval than for x = 0.1 show a similar evolution with temperature, even though the wide peak (P1) still exists at 400 K.

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