Local Anisotropy Fluctuation Research Articles

In-plane anisotropy studies in amorphous FeBSi films

Uniaxial anisotropy field, H/sub k/, and local anisotropy fluctuation were studied as a function of argon pressure during deposition for RF sputtered amorphous CoFeNb films. Influence of P/sub Ar/ on anistropy field H/sub k/, local anisotropy constant K/sub loc/, and S (structure constant) is discussed. The magnitude of S and K/sub loc/V/sup 1/2/ were found to be strongly dependent on P/sub Ar/. >

Soft magnetism of nanocrystalline Fe based sputtered films with high Bs

The physical origin of the high initial permeability, μ i, in Fe based films with a large magnetocrystalline anisotropy and magnetostriction is systematically discussed in connection with the microstructure of the films. In order to decrease the local anisotropy fluctuation to determine μ i, a decrease of the effective magnetic anisotropy, U eff, of each grain mainly caused by sufficient reduction of the grain size is required. Induced uniaxial magnetic anisotropy energy, K u, plays an important role to decrease U eff through the micromagnetic interaction. The ratio of U eff/ K u is proposed as the important key to analyze the magnetization process. The dependence of μ i on K u is classified concerning for U eff/ K u.

Soft Magnetic Properties of Ni-Fe-Nb Alloy Films with Nearly 50 wt% Ni Concentration

The relation between soft magnetic properties and local anisotropy fluctuation, which is strongly connected with the film microstructure, was systematically examined for Ni-Fe-Nb alloy films with nearly 50 wt% Ni. According to the micromagnetic ripple theory of Hoffmann, the effective magnetic anisotropy Ueff in each of the grains decreases drastically with increases in the number of grains N within the coupling volume. Experimental results showed that the local anisotropy fluctuation in Ni-Fe-Nb alloy films depends heavily on Ueff/K u , and decreases with decreasing Ueff/K u . Therefore, to realize high initial permeability in such films, it is necessary to increase N within the coupling volume by decreasing the grain size. In the cae of Ni-Fe-Nb alloy films, the grain size must be decreased to less than 200 A in order to obtain a high initial permeability more than 2000.

Soft Magnetic Properties and Microstructures for the Fe Based Sputtered Films with High Bs

ABSTRACTPhysical origin of high initial permeability, μi, in Fe based films with large magnetocrystalline anisotropy and magnetostriction is systematically discussed in connection with the microstructure of the films. In order to decrease the local anisotropy fluctuation to determine μi in these films, decrease of effective magnetic anisotropy, Ueff, of each grain mainly caused by the sufficient reduction of grain size is required. Induced uniaxial magnetic anisotropy energy, Ku, in film plane plays an important role to decrease Ueff through the micromagnetic interaction. The ratio of Ueff /Ku proposed as the important key to analyse the magnetization process. The dependence of μi Ku is classified concerning for Ueff/Ku.

Soft Magnetic Properties of Fe-Ni-Nb Alloy Films

The relation between the soft magnetic properties and local anisotropy fluctuation measured by the dynamic differential susceptibility method in Fe-Ni-Nb alloy films was clarified and discussed in comparison with Fe-Si-Al alloy films. Fe-Ni-Nb alloy films with excellent soft magnetic properties, 5 MHz values of ? eff = 6500 for 1000 A thick films were obtained. For Fe-Si-Al alloy films, the magnitude of ? eff = 6500 is proportional to 1/S2 (where S is a structure constant) and independent of the value of H k , while for Fe-Ni-Nb alloy films, the value of S is about one-tenth of that in Fe-Si-Al alloy films, and the magnitude of ? eff 6500 does not depend on S. Rather, this magnitude is dependent on the value of H k , and is almost equal to 4?M s /H k , obtained from a rotational magnetization model in a uniaxial single-domain particle.

Coercive field in amorphous Fe-R alloys

The coercive field ( H c) of amorphous Fe 1− x R x (R=Pr, Nd, Sm; 0.20≤ x≤0.60) alloys prepared by melt-quenching technique has been investigated in the temperature range of 77 K to RT. A simple wall-pinning model is proposed, suggesting that the coercive field of these amorphous alloys is mainly determined by fluctuations of local anisotropy. According to this model, one should observe a linear relationship between ln( MH c) and T in the narrow low temperature range, where M is the average magnetization of alloys.

Ｎｉ‐Ｆｅ‐Ｎｂ（５０Ｎｉ‐Ｆｅ組成）合金薄膜の軟磁気特性

The relation between soft magnetic properties and local anisotropy fluctuation, which is strongly connected with the microstructure of the films, was systematically examined for Ni-Fe-Nb alloy films with nearly 50 wt%Ni. According to the micromagnetic ripple theory by Hoffmann, effective magnetic anisotropy Ueff in each of the grains decreases drastically with increases in the number of grains N within the coupling volume. Experimental results show local anisotropy fluctuation for Ni-Fe-Nb alloy films strongly depends on Ueff/Ku, and it decreases with decreasing Ueff/Ku. Therefore, to realize high initial permeability in these films, it is necessary to increase N within the coupling volume by decreasing the size of the grains. In the case of Ni-Fe-Nb alloy films, decreasing the size of the grains less than 200A to obtain high initial permeability more than 2000 is needed.

Soft magnetic properties of Fe-Al-Si and Fe-Ni-Nb sputtered alloy films

The purpose of this experiment with the Fe-Si-Al thin film as an ordered structural alloy and the Fe-Ni-Nb thin film as a disordered structural alloy is to clarify the quantitative relationships and to improve the fabrication techniques in order to achieve improved soft magnetic properties. Thus, we examined in detail: 1) Concentration dependence of coercive force Hc and the effective permeability μeff. Furthermore, the relationship between μeff and the magnetocrystalline anisotropy and film magnetostriction. 2) The relationship between soft magnetic properties and the magnetic anisotropy field Hk, and the magnitude of long and short period local anisotropy fluctuation determined by the measurements of the dynamic differential susceptibility measurement. 3) The changes of μeff, Hk and long and short period local anisotropy fluctuation on a decrement of film thickness, in addition, the relationship between these amounts and K1 and λ.

Local Anisotropy Fluctuation on the Permeability of Sputtered Sendust Alloy Films

The precise concentration dependence of μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> in films was clarified in the concentration area around bulk Sendust alloy. The method of dynamic differential susceptibility measurement proposed by Hoffman was applied to these films to evaluate magnetic inhomogeneities normally represented as magnetic skew and ripple. Influence of the local magnetic anisotropy on the μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> of the films is discussed in detail. To realize excellent soft magnetic properties, especially at high frequency, a high degree of preferred orientation of grains or of random orientation of grains is suggested.

Ｆｅ‐Ｎｉ‐Ｎｂ系合金薄膜の軟磁気特性

Relation between soft magnetic properties and local anisotropy fluctuation in Fe-Ni-Nb alloy films measured by the dynamic differential susceptibility method was clarified and discussed in comparison with Fe-Si-Al alloy films. In Fe-Ni-Nb alloy films, excellent soft magnetic properties, μeff=6500 at 5 MHz of 1000Å film thickness, were realized. In Fe-Si-Al alloy films, the magnitude of μeff is proportional to 1/√S (S: structure constant) and independent of the value of HK, while in Fe-Ni-Nb alloy films, the value of S is about one tenth of that in Fe-Si-Al alloy films, and the magnitude of μeff is not dependent on the value of S. Rather, this magnitude is dependent on the value of Hk, and is almost equal to 4πMs/Hk (obtained from a rotational magnetization model in a uniaxal single domain particle).

Effect of Local Anisotropy Fluctuation on the Permeability of Fe-Si-Al Sputtered Films

Effect of Local Anisotropy Fluctuation on the Permeability of Fe-Si-Al Sputtered Films

Effect of Local Anisotropy Fluctuation on the Permeability of Multilayered Co-Zr-Mo-Ni Amorphous Films

To evaluate the magnetic inhomogeneities normally represented as magnetic skew and ripple, a systematic experimental investigation was carried out using the dynamic differential susceptibility measurement proposed by H. Hoffmann for multilayered CO79Zr10Mo9Ni2 amorphous films. The influence of the local magnetic anisotropy on the effective permeability μeff of the films is broadly discussed in connection with the magnetic skew and ripple. The magnitude of the μeff in low frequency regions less than 1 MHz is strongly dependent on the degree of the long period fluctuation of the local magnetization direction (skew) and the magnitude of the anisotropy field. To realize excellent soft magnetic properties in films at high frequencies (10 MHz), it is suggested that the alleviation of magnetic inhomogeneities due to the short-period fluctuation of the local magnetization direction is important.

Influence of local anisotropy fluctuation on soft magnetic properties of the sputtered Fe-Si-Al alloy films

Effective permeability, mu /sub eff/, uniaxial anisotropy field, H/sub k/, and local anisotropy fluctuation represented as magnetic ripple, SA/sup -5/8/ (S is the structure constant and A/sup -5/8/ is a coefficient equal to the power of the exchanges stiffness constant), were systematically studied as a function of composition and film thickness for Fe-Si-Al ternary alloy films. The influence of H/sub k/ and SA/sup -5/8/ on mu /sub eff/ is discussed in connection with the film structure. The magnitude of mu /sub eff/ was found to depend strongly on the magnitude of microscopic local anisotropy fluctuation. A decrease of the film thickness caused a marked increment in SA/sup -5/8/ due to the change of the preferred grain orientation from

Rotational relaxation of solute molecules in dense noble gases and the relation with local anisotropy fluctuations

Many molecular relaxation processes in fluids are sensitive to the time-dependence of local, anisotropic density fluctuations. The role played by anisotropic density fluctuations in the rotational relaxation of a linear, quantized rotor will be discussed in some detail. An expression for the dipolecorrelation function of a probe molecule, dissolved in a simple fluid, will be derived along these lines. This expression will be shown to account for the experimentally observed density-dependence of the rotational linewidths of HCl in argon. Some simple models for anisotropic density fluctuations or, more precisely, for the four-point density-correlation functions, will be discussed.