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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.


Dielectric properties of the FeCo-MgF nanogranular films.(a) Dielectric constant at 1 kHz (ε′1k) measured using an LCR meter vs the composition ratio of Fe+Co in FeCo-MgF films. The value of ε′1k is 5.6 at 0 at.%, and increases with increasing Fe+Co content, attaining 490 at 30 at.%. (b) Dielectric constant ε′ vs frequency f of FeCo-MgF films for Fe+Co=14, 17, 21, and 29 at.% measured in the frequency range of 1 kHz–1 MHz. The red dots represent the experimental results, and the blue solid lines represent the theoretical results obtained from calculations based on the spin-dependent dielectric relaxation model calculations (see formula (15)).
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f2: Dielectric properties of the FeCo-MgF nanogranular films.(a) Dielectric constant at 1 kHz (ε′1k) measured using an LCR meter vs the composition ratio of Fe+Co in FeCo-MgF films. The value of ε′1k is 5.6 at 0 at.%, and increases with increasing Fe+Co content, attaining 490 at 30 at.%. (b) Dielectric constant ε′ vs frequency f of FeCo-MgF films for Fe+Co=14, 17, 21, and 29 at.% measured in the frequency range of 1 kHz–1 MHz. The red dots represent the experimental results, and the blue solid lines represent the theoretical results obtained from calculations based on the spin-dependent dielectric relaxation model calculations (see formula (15)).

Mentions: Figure 2a shows the dependence of the real part of the dielectric constant at 1 kHz (ε′1k) on the composition ratio of the Fe+Co content in FeCo-MgF films. ε′1k of the Mg-F film produced in this experiment is about 5.6. This value is in agreement with the value of reference bulk MgF2 (ref. 20). On the other hand, the value of ε′1k of the films increases with the Fe+Co content, and attains 490 at 30 at.%. The frequency dependence of the real part of the dielectric constant (ε′) of the FeCo films at 14, 17, 21 and 29 at.% is presented in Fig. 2b. The ε′ increases with increasing Fe+Co over the whole frequency range, and exhibits a sharp decrease with increasing frequency. As discussed later, this dielectric dispersion may be caused by dielectric relaxation characterized by the relaxation time τr. The dielectric relaxation frequency fr=1/τr, at which ε′ sharply decreases, is shifted to the higher frequency side with increasing Fe+Co. As seen in Fig. 2, , FeCo-MgF nanogranular films have a giant dielectric constant of around 490, and fr shifts to the higher frequency side with increasing Fe+Co. Films having giant dielectric constant and high fr have high potentials for applications.


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

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

Dielectric properties of the FeCo-MgF nanogranular films.(a) Dielectric constant at 1 kHz (ε′1k) measured using an LCR meter vs the composition ratio of Fe+Co in FeCo-MgF films. The value of ε′1k is 5.6 at 0 at.%, and increases with increasing Fe+Co content, attaining 490 at 30 at.%. (b) Dielectric constant ε′ vs frequency f of FeCo-MgF films for Fe+Co=14, 17, 21, and 29 at.% measured in the frequency range of 1 kHz–1 MHz. The red dots represent the experimental results, and the blue solid lines represent the theoretical results obtained from calculations based on the spin-dependent dielectric relaxation model calculations (see formula (15)).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Dielectric properties of the FeCo-MgF nanogranular films.(a) Dielectric constant at 1 kHz (ε′1k) measured using an LCR meter vs the composition ratio of Fe+Co in FeCo-MgF films. The value of ε′1k is 5.6 at 0 at.%, and increases with increasing Fe+Co content, attaining 490 at 30 at.%. (b) Dielectric constant ε′ vs frequency f of FeCo-MgF films for Fe+Co=14, 17, 21, and 29 at.% measured in the frequency range of 1 kHz–1 MHz. The red dots represent the experimental results, and the blue solid lines represent the theoretical results obtained from calculations based on the spin-dependent dielectric relaxation model calculations (see formula (15)).
Mentions: Figure 2a shows the dependence of the real part of the dielectric constant at 1 kHz (ε′1k) on the composition ratio of the Fe+Co content in FeCo-MgF films. ε′1k of the Mg-F film produced in this experiment is about 5.6. This value is in agreement with the value of reference bulk MgF2 (ref. 20). On the other hand, the value of ε′1k of the films increases with the Fe+Co content, and attains 490 at 30 at.%. The frequency dependence of the real part of the dielectric constant (ε′) of the FeCo films at 14, 17, 21 and 29 at.% is presented in Fig. 2b. The ε′ increases with increasing Fe+Co over the whole frequency range, and exhibits a sharp decrease with increasing frequency. As discussed later, this dielectric dispersion may be caused by dielectric relaxation characterized by the relaxation time τr. The dielectric relaxation frequency fr=1/τr, at which ε′ sharply decreases, is shifted to the higher frequency side with increasing Fe+Co. As seen in Fig. 2, , FeCo-MgF nanogranular films have a giant dielectric constant of around 490, and fr shifts to the higher frequency side with increasing Fe+Co. Films having giant dielectric constant and high fr have high potentials for applications.

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.