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  Magnetic film for magnetic headUSPTO Application #: 20080107922Title: Magnetic film for magnetic head Abstract: The magnetic film includes an FeCo layer, restrains erasing data by a magnetic field leaked from a magnetic pole, has high saturation magnetic flux density and soft magnetism and writes data with high recording density. The magnetic film for a magnetic head of the present invention comprises: a nonmagnetic layer including at least one selected from a group of Ru, Rh, Ir, Cr, Cu, Au, Ag, Pt and Pd; a magnetic layer including Fe and Co. Anisotropy magnetic field is 0.8 kA/m or more. (end of abstract) Agent: Greer, Burns & Crain - Chicago, IL, US Inventors: Shoji Ikeda, Takayuki Kubomiya, Masaaki Matsuoka USPTO Applicaton #: 20080107922 - Class: 428812000 (USPTO) Related Patent Categories: Stock Material Or Miscellaneous Articles, Magnetic Recording Component Or Stock, Magnetic Head, Magnetic Layer Composition The Patent Description & Claims data below is from USPTO Patent Application 20080107922. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This is a divisional of application Ser. No. 10/786,840, filed Feb. 25, 2004. BACKGROUND OF THE INVENTION [0002] The present invention relates to a magnetic film for a magnetic head, more precisely relates to a magnetic film for a write-head of a magnetic head, especially a perpendicular recording head, which is capable of intensifying a writing magnetic field, improving magnetic response and raising recording density. [0003] Conventionally, many elements have been used for multilayered magnetic films so as to achieve many purposes. For example, a giant magnetic resistance was found in a Fe/Cr multilayered film, so that a spin valve film for a read-head was invented (see Phys. Rev. Lett., vol. 62, p. 2472 (1988)). A Co/Pd multilayered film has greater perpendicular magnetic anisotropy than a CoCr alloy film, so it will be used for recording media (see J. Appl. Phys., vol. 87, p. 6887 (1988)). Layer stacking separations of the conventional multilayered films are several nm, and each of the layers is very thin and constituted by several atomic layers. [0004] On the other hand, a NiFe single layer film, whose saturation magnetic flux density (Bs) is 1-1.5 T, has been used as a conventional material of a write-head. Thickness of the film is several .mu.m, namely the film is a thick one. In the future, a data transfer rate of a magnetic disk drive unit will be accelerated. Eddy current loss occurs in the thick magnetic film, so that writing performance of the write-head is made worse. To solve the problem, a multilayered film, in which magnetic layers and insulating layers are alternately piled, has been studied. In the multilayered film, resistance of the insulating layers and the magnetic layers is high, and the thickness of the film is less than skin depth, e.g., submicron, so that eddy current loss can be restricted. [0005] To make magnetic anisotropy small and gain enough soft magnetism, amorphous, micro crystals and granular magnetic films have been studied as the magnetic layer. Further, by employing the multilayered structure, the magnetic layers are statically magnetic-connected, so that a magnetic circuit is closed and frequency response can be improved. According to J. Magn. Soc. Jpn. vol. 14, p. 379 (1990) and J. Magn. Soc. Jpn. vol. 15, p. 391 (1991), an amorphous metal CoNbZr and a micro crystal FeSiN are used as materials of the magnetic layers. Saturation magnetic flux density of the magnetic layers is 0.8-1.85 T. However, recording density will be even higher, so a track width and a pole length of a front end section of a magnetic pole must be smaller so as to write smaller bits. [0006] Further, coercivity of recording media will be increased so as to limit thermal decay of magnetization of magnetic minute particles. Magnetic materials must have high saturation magnetic flux density (Bs) to generate a higher magnetic field for writing data. Therefore, enough magnetic fields cannot be generated with amorphous and microcrystal materials, whose Bs is 0.8-1.85 T. An FeCo alloy is a thermal equilibrium alloy having maximum Bs of 2.45 T, but its magnetostriction constant (.lamda.) is large, e.g., 30-70.times.10.sup.-6, so a inverse magnetostrictive effect, which is caused by isotropic stress generated while a layer is formed, cannot be ignored. Therefore, it is very difficult for the FeCo single layer to have soft magnetism with uniaxial magnetic anisotropy. In the case of using a magnetic material having isotropic magnetic characteristics as magnetic poles, data recorded on a recording media are apt to be erased by a leaked magnetic field corresponding to a residual magnetization (Br). [0007] Erasing data by a write-head is more remarkable in a single pole type head for perpendicular magnetic recording than a ring head for longitudinal recording. Further, a front end of the single pole type head is formed like a needle. Even if a magnetic material in a state of as-depositing has uniaxial magnetic anisotropy and its Br in a direction of the hard axis is reduced, a leaked magnetic field is generated by shape magnetic anisotropy caused by the shape of the magnetic pole, so that there is possibility of erasing data by the leaked magnetic field. To solve the problem, a magnetic material, which has high Bs and which is capable of restraining uniaxial magnetic anisotropy and shape magnetic anisotropy, is required. [0008] To increase Bs, adding impurities, which accelerate crystal growth, must be restrained. In crystal magnetic materials, e.g., FeCo, columnar growth and enlarging crystals in a thickness direction of a layer are more remarkable than those in amorphous and glanular alloy films. Therefore, roughness of a surface of a layer or unevenness of crystals obstruct to form multilayer with other materials. Namely, materials must be selected with fully considering the roughness. [0009] In the FeCo single layer, a underlayer is formed immediately under the FeCo alloy layer so as to have soft magnetism with high Bs. According to IEEE. Trans. Magn. vol. 36 p. 2506-2508 (2000), an FeCoN magnetic layer has soft magnetism and high Bs, e.g., 2.4 T. However, it is difficult to control magnetic anisotropy of the FeCoN single layer. To solve this problem, the FeCoN layer is formed on a underlayer, which is made of permalloy of Ni.sub.80Fe.sub.20, or the FeCoN layer is sandwiched between the layers made of the permalloy of Ni.sub.80Fe.sub.20, so that the soft magnetism is improved. In said report, thickness of the FeCoN layer is 0.1 .mu.m, and there is no description about soft magnetism of the layer whose thickness is more than 0.1 .mu.m. To enhance the writing magnetic field, it is effective to make thickness of a high Bs layer of a front end of a magnetic pole 0.1 .mu.m or more. By forming the FeCoN layer on the NiFe underlayer, the soft magnetism is improved by magnetic coupling between the two layers. And, magnetoelastic anisotropy, which is caused by residual stress generated while a layer is formed, is not dominant. [0010] On the other hand, in IEEE. Trans. Magn. vol. 38 p. 2225-2227 (2002), a underlayer made of a nonmagnetic material (NiFeCr) is disclosed. The underlayer is capable of improving the soft magnetism of FeCo as well as the underlayer made of NiFe. The fact means that the magnetic coupling between the underlayer and the FeCoN layer is not an essential factor of improving the soft magnetism. The magnetic layer having high Bs and soft magnetism is required so as to write data in a recording media, which has a high coercivity and high recording density, with high writing accuracy and improve magnetic response. However, FeCo layers, which have such required properties, have not developed. SUMMARY OF THE INVENTION [0011] To solve the problem of erasing data by the magnetic field leaked from a magnetic pole, there are several ways, for example: giving uniaxial magnetic anisotropy to a magnetic layer; closing a magnetic circuit by a multilayered film, in which a magnetic layer and a nonmagnetic layer are static-magnetically coupled; and accelerating antiparallel magnetization sequence between magnetic layers by exchange coupling so as to increase a saturated magnetic field (Hs). Therefore, materials, which restrain residual stress in layers, give uniaxial magnetic anisotropy to nonmagnetic layers (a underlayer and/or an intermediate layer), close a magnetic circuit between magnetic layers and generate antiferromagnetic coupling between magnetic layers, are required. Further, if a surface of an FeCo layer is rough, a nonmagnetic layer cannot magnetically insulate FeCo layers, so that the magnetic circuit between the magnetic layers cannot be closed and the antiferromagnetic coupling disappears. Therefore, the roughness must be controlled. [0012] An object of the present invention is to provide a magnetic film for a magnetic head, which includes an FeCo layer, restrains erasing data by a magnetic field leaked from a magnetic pole, has high saturation magnetic flux density and soft magnetism and writes data with high recording density. [0013] To achieve the object, the present invention has following structures. [0014] Namely, the magnetic film for a magnetic head of the present invention comprises: a nonmagnetic layer including at least one selected from a group of Ru, Rh, Ir, Cr, Cu, Au, Ag, Pt and Pd; a magnetic layer including Fe and Co, wherein anisotropy magnetic field is 0.8 kA/m or more. [0015] In the magnetic film, the saturation magnetic flux density may have uniaxial magnetic anisotropy, and residual stress in the film may be .+-.0.5 GPa or less. [0016] Another magnetic film of the present invention comprises: nonmagnetic layers, each of which has a first layer section and a second layer section; and magnetic layers, each of which includes Fe and Co, wherein the first layer section and the second layer section are respectively include at least one selected from a group of Ru, Rh, Ir, Cr, Cu, Au, Ag, Pt and Pd, the nonmagnetic layer and the magnetic layer are alternately piled, and thickness of each magnetic layer is 100 nm or less. With this structure, roughness of the surface can be improved, so that generating a leaked magnetic field, which leaks from a magnetic pole to a recording meda, can be restrained and erasing recorded data can be prevented. [0017] In the magnetic film, the magnetic layer may include 40-80 at % of Fe. [0018] And, the magnetic film of the present invention comprises: a nonmagnetic layer, which has a first layer section and a second layer section; and a magnetic layer, which includes Fe and Co, wherein the first layer section and the second layer section are respectively include at least one selected from a group of Ru, Rh, Ir, Cr, Cu, Au, Ag, Pt and Pd, boundary parts of the magnetic layer, which contact the nonmagnetic layer, includes 30-65 at % of Fe, and an intermediate part of the magnetic layer, which is formed between the boundary parts, includes 40-80 at % of Fe. [0019] In the magnetic film, thickness of the magnetic layer may be 100 nm or less. [0020] Further, the magnetic film for a magnetic head includes Fe and Co as main elements, wherein the magnetic film has a body-centered cubic lattice structure, in which intensity ratio of (110) and (211) crystal planes in a film growth direction is I(211)/I(110)=2-100%. With this structure, the magnetic film has high saturation magnetic flux density and good soft magnetism. Crystal orientation of the FeCo magnetic film can be controlled on the basis of intensity ratio of X-ray diffraction, so that a recording magnetic field can be increased and magnetic response of a magnetic pole can be improved. Therefore, the magnetic head using the magnetic film is capable of recording data with high density. [0021] In the magnetic film, the magnetic film may have uniaxial magnetic anisotropy having a easy axis of magnetization and a hard axis of magnetization, a coercivity of the hard axis of magnetization may be 0.8 kA/m or less, and residual magnetization ratio of the hard axis of magnetization (Brh/Bsh) may be 30% or less. [0022] The magnetic films of the present invention are capable of providing high writing magnetic fields and good magnetic response, so they can be used for magnetic heads capable of writing data with high recording density. By piling the magnetic layer and the nonmagnetic layer, a recording magnetic field can be increased, and the leaked magnetic field, which is leaked from the magnetic pole and erases recorded data, can be restrained. Therefore, reliability of recording data and recording density can be improved. Continue reading... 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