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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

The structure and magnetic properties of CoFeB/PVDF at room temperature.(a) Schematic view of the PVDF substrate. (b) XRD pattern of PVDF substrate. Inset: TEM results for CoFeB films. (c) The magnetic hysteresis loops of CoFeB/PVDF with H parallel (along x direction) and perpendicular to the plane of CoFeB film at 300 K (d) The angular dependence of normalized remanent magnetization Mr/Ms with fitting line at 300 K. The dashed line is cos2φ fitting.
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f1: The structure and magnetic properties of CoFeB/PVDF at room temperature.(a) Schematic view of the PVDF substrate. (b) XRD pattern of PVDF substrate. Inset: TEM results for CoFeB films. (c) The magnetic hysteresis loops of CoFeB/PVDF with H parallel (along x direction) and perpendicular to the plane of CoFeB film at 300 K (d) The angular dependence of normalized remanent magnetization Mr/Ms with fitting line at 300 K. The dashed line is cos2φ fitting.

Mentions: It is well known that, in strain-mediated ferromagnetic/ferroelectric (FM/FE) bilayers, a uniaxial strain produced through converse piezoelectric effect when an electric field applied on FE layer can be transferred to FM layer to manipulate the magnetic anisotropy1819. Thus, if a functional layer can generate a uniaxial strain when changing the temperature, the positive temperature coefficient of magnetic anisotropy can be realized in bilayers structure through strain-induce anisotropy. β-phase polyvinylidene fluoride (PVDF) and its copolymer, i.e. PVDF-trifluoroethlene (PVDF-TrEE) are well-known ferroelectric materials showing widely applications in information storage, field-effect transistors, sensors and actuators202122. Besides the ferroelectric properties, PVDF also has an anisotropic thermal expansion, which can generate a uniaxial strain when changing the temperature23. We report here the realization of positive temperature coefficient of magnetic anisotropy in magnetic film/PVDF bilayers. The enhanced magnetic anisotropy with increasing temperature originates from the strain-induced anisotropy resulting from the anisotropic thermal expansion of β-phase PVDF substrate (Figure 1a).


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)

The structure and magnetic properties of CoFeB/PVDF at room temperature.(a) Schematic view of the PVDF substrate. (b) XRD pattern of PVDF substrate. Inset: TEM results for CoFeB films. (c) The magnetic hysteresis loops of CoFeB/PVDF with H parallel (along x direction) and perpendicular to the plane of CoFeB film at 300 K (d) The angular dependence of normalized remanent magnetization Mr/Ms with fitting line at 300 K. The dashed line is cos2φ fitting.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: The structure and magnetic properties of CoFeB/PVDF at room temperature.(a) Schematic view of the PVDF substrate. (b) XRD pattern of PVDF substrate. Inset: TEM results for CoFeB films. (c) The magnetic hysteresis loops of CoFeB/PVDF with H parallel (along x direction) and perpendicular to the plane of CoFeB film at 300 K (d) The angular dependence of normalized remanent magnetization Mr/Ms with fitting line at 300 K. The dashed line is cos2φ fitting.
Mentions: It is well known that, in strain-mediated ferromagnetic/ferroelectric (FM/FE) bilayers, a uniaxial strain produced through converse piezoelectric effect when an electric field applied on FE layer can be transferred to FM layer to manipulate the magnetic anisotropy1819. Thus, if a functional layer can generate a uniaxial strain when changing the temperature, the positive temperature coefficient of magnetic anisotropy can be realized in bilayers structure through strain-induce anisotropy. β-phase polyvinylidene fluoride (PVDF) and its copolymer, i.e. PVDF-trifluoroethlene (PVDF-TrEE) are well-known ferroelectric materials showing widely applications in information storage, field-effect transistors, sensors and actuators202122. Besides the ferroelectric properties, PVDF also has an anisotropic thermal expansion, which can generate a uniaxial strain when changing the temperature23. We report here the realization of positive temperature coefficient of magnetic anisotropy in magnetic film/PVDF bilayers. The enhanced magnetic anisotropy with increasing temperature originates from the strain-induced anisotropy resulting from the anisotropic thermal expansion of β-phase PVDF substrate (Figure 1a).

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