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Positive temperature coefficient of magnetic anisotropy in polyvinylidene fluoride (PVDF)-based magnetic composites.

Liu Y, Wang B, Zhan Q, Tang Z, Yang H, Liu G, Zuo Z, Zhang X, Xie Y, Zhu X, Chen B, Wang J, Li RW - Sci Rep (2014)

Bottom Line: We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the strain-induced anisotropy resulting from the anisotropic thermal expansion of the β-phase PVDF.The simulation based on modified Stoner-Wohlfarth model and the ferromagnetic resonance measurements confirms our results.The present results may help to design magnetic devices with improved thermal stability and enhanced performance.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Magnetic Materials and Devices &Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo 315201, People's Republic of China.

ABSTRACT
The magnetic anisotropy is decreased with increasing temperature in normal magnetic materials, which is harmful to the thermal stability of magnetic devices. Here, we report the realization of positive temperature coefficient of magnetic anisotropy in a novel composite combining β-phase polyvinylidene fluoride (PVDF) with magnetostrictive materials (magnetostrictive film/PVDF bilayer structure). We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the strain-induced anisotropy resulting from the anisotropic thermal expansion of the β-phase PVDF. The simulation based on modified Stoner-Wohlfarth model and the ferromagnetic resonance measurements confirms our results. The positive temperature coefficient of magnetic anisotropy is estimated to be 1.1 × 10(2) J m(-3) K(-1). Preparing the composite at low temperature can enlarge the temperature range where it shows the positive temperature coefficient of magnetic anisotropy. The present results may help to design magnetic devices with improved thermal stability and enhanced performance.

No MeSH data available.


Related in: MedlinePlus

Temperature dependence of magnetic properties of other PVDF-based magnetic films.In-plane magnetic hysteresis loops measured along x direction at various temperatures for (a) FeGa/PVDF and (b) Ni/PVDF. The temperature dependence of the remanent magnetization with H along x and y directions for (c) FeGa/PVDF and (d) Ni/PVDF.
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f3: Temperature dependence of magnetic properties of other PVDF-based magnetic films.In-plane magnetic hysteresis loops measured along x direction at various temperatures for (a) FeGa/PVDF and (b) Ni/PVDF. The temperature dependence of the remanent magnetization with H along x and y directions for (c) FeGa/PVDF and (d) Ni/PVDF.

Mentions: In order to know the temperature dependence of magnetic anisotropy for different magnetostrictive films, we prepared two other composites by depositing different magnetic materials on PVDF: one is positive magnetostrictive FeGa and the other is negative magnetostrictive Ni. Figure 3a and 3b show the temperature dependence of magnetic hysteresis loops measured with H along x direction for FeGa/PVDF and Ni/PVDF, respectively. For FeGa/PVDF, the slanted loop is changed to a square one with increasing temperature from 280 to 320 K, which is similar to that observed for CoFeB/PVDF. However, for Ni/PVDF, the square loop is changed to a slanted one with increasing temperature. Figure 3c and 3d show the temperature dependence of the remanent magnetization along both x and y directions for FeGa/PVDF and Ni/PVDF, respectively. Both FeGa/PVDF and Ni/PVDF show easy axis reorientation. The temperature dependence of Mr/Ms for FeGa/PVDF is similar to that for CoFeB/PVDF. But the change of Mr/Ms with H along x is about 0.62, which is larger than that observed for CoFeB/PVDF. This is likely due to the fact that FeGa possess a larger magnetostrictive coefficient than CoFeB. On the other hand, the temperature dependence of Mr/Ms for Ni/PVDF shows an opposite behavior. With increasing temperature from 280 to 320 K, Mr/Ms decreases from 0.45 to 0.08 and increases from 0.26 to 0.48 for H along x and y direction, respectively. The change of Mr/Ms with H along x for Ni/PVDF is about 0.37, which is similar to the value of CoFeB/PVDF due to the comparable magnetostrictive coefficients for CoFeB and Ni. Nevertheless, both FeGa/PVDF and Ni/PVDF composites show enhanced magnetic anisotropy with increasing temperature. The only difference is the direction of easy axis at high temperature. The results confirm that it is possible to design PVDF-based magnetic films with specific temperature dependence of magnetic anisotropy by combining the positive and negative magnetostrictive films (Figure S3).


Positive temperature coefficient of magnetic anisotropy in polyvinylidene fluoride (PVDF)-based magnetic composites.

Liu Y, Wang B, Zhan Q, Tang Z, Yang H, Liu G, Zuo Z, Zhang X, Xie Y, Zhu X, Chen B, Wang J, Li RW - Sci Rep (2014)

Temperature dependence of magnetic properties of other PVDF-based magnetic films.In-plane magnetic hysteresis loops measured along x direction at various temperatures for (a) FeGa/PVDF and (b) Ni/PVDF. The temperature dependence of the remanent magnetization with H along x and y directions for (c) FeGa/PVDF and (d) Ni/PVDF.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4196102&req=5

f3: Temperature dependence of magnetic properties of other PVDF-based magnetic films.In-plane magnetic hysteresis loops measured along x direction at various temperatures for (a) FeGa/PVDF and (b) Ni/PVDF. The temperature dependence of the remanent magnetization with H along x and y directions for (c) FeGa/PVDF and (d) Ni/PVDF.
Mentions: In order to know the temperature dependence of magnetic anisotropy for different magnetostrictive films, we prepared two other composites by depositing different magnetic materials on PVDF: one is positive magnetostrictive FeGa and the other is negative magnetostrictive Ni. Figure 3a and 3b show the temperature dependence of magnetic hysteresis loops measured with H along x direction for FeGa/PVDF and Ni/PVDF, respectively. For FeGa/PVDF, the slanted loop is changed to a square one with increasing temperature from 280 to 320 K, which is similar to that observed for CoFeB/PVDF. However, for Ni/PVDF, the square loop is changed to a slanted one with increasing temperature. Figure 3c and 3d show the temperature dependence of the remanent magnetization along both x and y directions for FeGa/PVDF and Ni/PVDF, respectively. Both FeGa/PVDF and Ni/PVDF show easy axis reorientation. The temperature dependence of Mr/Ms for FeGa/PVDF is similar to that for CoFeB/PVDF. But the change of Mr/Ms with H along x is about 0.62, which is larger than that observed for CoFeB/PVDF. This is likely due to the fact that FeGa possess a larger magnetostrictive coefficient than CoFeB. On the other hand, the temperature dependence of Mr/Ms for Ni/PVDF shows an opposite behavior. With increasing temperature from 280 to 320 K, Mr/Ms decreases from 0.45 to 0.08 and increases from 0.26 to 0.48 for H along x and y direction, respectively. The change of Mr/Ms with H along x for Ni/PVDF is about 0.37, which is similar to the value of CoFeB/PVDF due to the comparable magnetostrictive coefficients for CoFeB and Ni. Nevertheless, both FeGa/PVDF and Ni/PVDF composites show enhanced magnetic anisotropy with increasing temperature. The only difference is the direction of easy axis at high temperature. The results confirm that it is possible to design PVDF-based magnetic films with specific temperature dependence of magnetic anisotropy by combining the positive and negative magnetostrictive films (Figure S3).

Bottom Line: We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the strain-induced anisotropy resulting from the anisotropic thermal expansion of the β-phase PVDF.The simulation based on modified Stoner-Wohlfarth model and the ferromagnetic resonance measurements confirms our results.The present results may help to design magnetic devices with improved thermal stability and enhanced performance.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Magnetic Materials and Devices &Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo 315201, People's Republic of China.

ABSTRACT
The magnetic anisotropy is decreased with increasing temperature in normal magnetic materials, which is harmful to the thermal stability of magnetic devices. Here, we report the realization of positive temperature coefficient of magnetic anisotropy in a novel composite combining β-phase polyvinylidene fluoride (PVDF) with magnetostrictive materials (magnetostrictive film/PVDF bilayer structure). We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the strain-induced anisotropy resulting from the anisotropic thermal expansion of the β-phase PVDF. The simulation based on modified Stoner-Wohlfarth model and the ferromagnetic resonance measurements confirms our results. The positive temperature coefficient of magnetic anisotropy is estimated to be 1.1 × 10(2) J m(-3) K(-1). Preparing the composite at low temperature can enlarge the temperature range where it shows the positive temperature coefficient of magnetic anisotropy. The present results may help to design magnetic devices with improved thermal stability and enhanced performance.

No MeSH data available.


Related in: MedlinePlus