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Giant dielectric and magnetoelectric responses in insulating nanogranular films at room temperature.

Kobayashi N, Masumoto H, Takahashi S, Maekawa S - Nat Commun (2014)

Bottom Line: In these films, Fe-Co alloy-based nanometer-sized magnetic granules are dispersed in a Mg-fluoride-based insulator matrix.Insulating nanogranular films are a new class of multifunctional materials.A possible application of such insulating nanogranular materials with giant response is in the construction of a tunable device, in which impedance components such as capacitance and inductance are tunable at room temperature.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Electromagnetic Materials, 2-1-1,Yagiyama-minami, Taihaku-ku, Sendai 982-0807, Japan.

ABSTRACT
The electric and magnetic properties of matter are of great interest for materials science and their use in electronic applications. Large dielectric and magnetoelectric responses of materials at room temperature are a great advantage for electromagnetic device applications. Here we present a study of FeCo-MgF nanogranular films exhibiting giant dielectric and magnetoelectric responses at room temperature; with dielectric constant ε'=490 and magnetoelectric response Δε'/ε'0=3%. In these films, Fe-Co alloy-based nanometer-sized magnetic granules are dispersed in a Mg-fluoride-based insulator matrix. Insulating nanogranular films are a new class of multifunctional materials. The giant responses are caused by spin-dependent charge oscillation between magnetic granules via quantum-mechanical tunnelling. A possible application of such insulating nanogranular materials with giant response is in the construction of a tunable device, in which impedance components such as capacitance and inductance are tunable at room temperature.

No MeSH data available.


Derivation of the dielectric constant.(a) Ferromagnetic metal granules 1 and 2 embedded in insulating matrix. (b) A double potential wells illustrating an electric polarization due to tunneling of charge (electron) through the barrier from one well to the other back and forth under the ac electric field E(t). (c) The real parts of the dielectric constant are calculated from the equation (1) for three different values of β. The lines show the results of fitting values of β=0.6, 0.75, and 0.9, (Δε=185 (εs=195, ε∞=10), τr=1.65 × 10−5 s), and the circles represent the experimental results.
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f6: Derivation of the dielectric constant.(a) Ferromagnetic metal granules 1 and 2 embedded in insulating matrix. (b) A double potential wells illustrating an electric polarization due to tunneling of charge (electron) through the barrier from one well to the other back and forth under the ac electric field E(t). (c) The real parts of the dielectric constant are calculated from the equation (1) for three different values of β. The lines show the results of fitting values of β=0.6, 0.75, and 0.9, (Δε=185 (εs=195, ε∞=10), τr=1.65 × 10−5 s), and the circles represent the experimental results.

Mentions: We derive the dielectric constant of a granular system composed of ferromagnetic granules of nanometer size in an insulating matrix. In a granular system, the transport is governed by thermally activated charge carriers that move from granule to neighbouring granule by tunnelling through an insulating barrier. Depending on the separation and tunnel barrier height, a charge carrier activated in one granule may tunnel to another. A simple model for a pair of granules 1 and 2 and the double potential well is schematically shown in Fig. 6a,b. In the absence of applied ac electric field, the transition rate between the two granules is determined by the charging energies and the tunnelling process2529:


Giant dielectric and magnetoelectric responses in insulating nanogranular films at room temperature.

Kobayashi N, Masumoto H, Takahashi S, Maekawa S - Nat Commun (2014)

Derivation of the dielectric constant.(a) Ferromagnetic metal granules 1 and 2 embedded in insulating matrix. (b) A double potential wells illustrating an electric polarization due to tunneling of charge (electron) through the barrier from one well to the other back and forth under the ac electric field E(t). (c) The real parts of the dielectric constant are calculated from the equation (1) for three different values of β. The lines show the results of fitting values of β=0.6, 0.75, and 0.9, (Δε=185 (εs=195, ε∞=10), τr=1.65 × 10−5 s), and the circles represent the experimental results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109019&req=5

f6: Derivation of the dielectric constant.(a) Ferromagnetic metal granules 1 and 2 embedded in insulating matrix. (b) A double potential wells illustrating an electric polarization due to tunneling of charge (electron) through the barrier from one well to the other back and forth under the ac electric field E(t). (c) The real parts of the dielectric constant are calculated from the equation (1) for three different values of β. The lines show the results of fitting values of β=0.6, 0.75, and 0.9, (Δε=185 (εs=195, ε∞=10), τr=1.65 × 10−5 s), and the circles represent the experimental results.
Mentions: We derive the dielectric constant of a granular system composed of ferromagnetic granules of nanometer size in an insulating matrix. In a granular system, the transport is governed by thermally activated charge carriers that move from granule to neighbouring granule by tunnelling through an insulating barrier. Depending on the separation and tunnel barrier height, a charge carrier activated in one granule may tunnel to another. A simple model for a pair of granules 1 and 2 and the double potential well is schematically shown in Fig. 6a,b. In the absence of applied ac electric field, the transition rate between the two granules is determined by the charging energies and the tunnelling process2529:

Bottom Line: In these films, Fe-Co alloy-based nanometer-sized magnetic granules are dispersed in a Mg-fluoride-based insulator matrix.Insulating nanogranular films are a new class of multifunctional materials.A possible application of such insulating nanogranular materials with giant response is in the construction of a tunable device, in which impedance components such as capacitance and inductance are tunable at room temperature.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Electromagnetic Materials, 2-1-1,Yagiyama-minami, Taihaku-ku, Sendai 982-0807, Japan.

ABSTRACT
The electric and magnetic properties of matter are of great interest for materials science and their use in electronic applications. Large dielectric and magnetoelectric responses of materials at room temperature are a great advantage for electromagnetic device applications. Here we present a study of FeCo-MgF nanogranular films exhibiting giant dielectric and magnetoelectric responses at room temperature; with dielectric constant ε'=490 and magnetoelectric response Δε'/ε'0=3%. In these films, Fe-Co alloy-based nanometer-sized magnetic granules are dispersed in a Mg-fluoride-based insulator matrix. Insulating nanogranular films are a new class of multifunctional materials. The giant responses are caused by spin-dependent charge oscillation between magnetic granules via quantum-mechanical tunnelling. A possible application of such insulating nanogranular materials with giant response is in the construction of a tunable device, in which impedance components such as capacitance and inductance are tunable at room temperature.

No MeSH data available.