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  Magnetic oscillator, magnetic head, and magnetic recording and reproducing apparatusUSPTO Application #: 20060039089Title: Magnetic oscillator, magnetic head, and magnetic recording and reproducing apparatus Abstract: The present invention is to be capable of suppressing magnetic white noises as far as possible. A resonant magneto-resistance effect element includes a first magnetic layer whose magnetization direction is substantially parallel to a film plane, a second magnetic film whose magnetization direction is substantially perpendicular to the film plane, and a non-magnetic layer which is provided between the first and second layers. (end of abstract)
Agent: Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US Inventor: Rie Sato USPTO Applicaton #: 20060039089 - Class: 360324000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060039089. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-237463 filed on Aug. 17, 2004 in Japan, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a magnetic oscillator, a magnetic head, and a magnetic recording and reproducing apparatus. [0004] 2. Related Art [0005] Since advent of a GMR (giant magneto-resistance) head utilizing a giant magneto-resistance effect (GMR effect), a recording density in magnetic recording is improved at 100% annually. The GMR element is constituted of a stacked film having a sandwich structure of a ferromagnetic layer/a non-magnetic layer/a ferromagnetic layer. The GMR element is a device utilizing a magneto-resistance effect of a so-called spin valve film, which is constituted such that magnetization of one of the ferromagnetic layers is pinned by application of exchange bias to the one and a magnetization direction of the other thereof is changed by applying external magnetic field thereto, so that change in an angle angle defined between the magnetization directions of the two ferromagnetic layers is detected as a change in resistance value. There have been developed a CIP (current in plane)-GMR element which causes current to flow in a film plane of a spin valve film to detect a resistance change and a CPP (current perpendicular to plane)-GMR element which causes current to flow perpendicularly to a film plane of a spin valve film to detect a resistance change. Both the CIP-GMR element and the CPP-GMR element have a magneto-resistance ratio (MR ratio) of several % or so, and it is considered that both the elements can accommodate a recording density of about 200 Gbit/inch.sup.2. [0006] In order to accommodate magnetic recording at a higher density, development of a TMR element utilizing a tunneling magneto-resistance effect (TMR effect) has been gone ahead. The TMR element comprises a stacked film of a ferromagnetic layer/an insulating layer/a ferromagnetic layer, and it causes a tunnel current to flow in the insulating layer on application of a voltage between the ferromagnetic layers. The TMR element is an element which utilizes such a fact that the magnitude of a tunnel current is changed according to the magnetization directions of the upper and lower ferromagnetic layers to detect change of an angle defined by the magnetization directions as a tunnel resistance value. A TMR element having an MR ratio up to about 50% has been obtained. Since the TMR element has a MR ratio larger than that of the GMR element, its signal voltage becomes larger. [0007] However, there is such a problem that not only a pure signal component but also a noise component due to a shot noise become large, and an S/N ratio (a signal-noise ratio) is not improved. The shot noise is caused by current fluctuation generated due to irregular passing of electrons through a tunnel barrier, and it increases in proportion to square root of a tunnel resistance value. In order to suppress the shot noise and obtain a required signal voltage, therefore, it is necessary to make a tunnel insulating layer thin to lower a tunnel resistance. [0008] Since it is necessary to reduce a device size to a size corresponding to a recording bit or so according to increase in recording density, it is necessary to lower a junction resistance of a tunnel insulating layer, namely, make the insulating layer thin, according to increase in density. A junction resistance of 1 .OMEGA.cm.sup.2 or less is required in a recording density of 300 Gbit/inch.sup.2 and therefore a tunnel insulating layer with a thickness corresponding to a thickness of two atoms must be formed in terms of a film thickness of an Al--O (aluminum oxide film) tunnel insulating layer. Since shortage between the upper and lower electrodes becomes easier to occur according to thinning of the tunnel insulating layer, which leads to reduction of a MR ratio, it becomes exponentially difficult to manufacture an element. Therefore, the limit of the TMR element is estimated to be 300 Gbit/inch.sup.2. [0009] The respective elements described above utilize the magneto-resistance effect in a board sense, but a problem about a magnetic white noise common to these elements emerges suddenly in recent years. Since the noise is different from an electric noise such as the shot noise described above and is due to thermal fluctuation of magnetization, it is thought that the noise becomes more dominant according to fineness of an element so that the white noise outstrips the electric noise in an element corresponding to 200 Gbpis to 300 Gbpsi. In order to avoid the magnetic white noise and further increase a recording density in magnetic recording, a fine magnetic sensor operating based upon a principle different from the conventional magneto-resistance effect is required, and development of a resonant magneto-resistance effect element has been gone ahead as such a magnetic sensor (for example, see R. Sato, et. al. J. Magn. Magn. Mat. Vol. 279, p. 36 (2004)). [0010] A characteristic improvement of a conventional resonant magneto-resistance effect element has been promoted by using artificial anti-ferromagnetic material with reduced defect as magnetic material in a structure where a non-magnetic layer with a thickness of 1 nm or less is sandwiched between ferromagnetic layers whose magnetization directions are perpendicular to a film plane. However, the artificial ferromagnetic material includes many difficult points for practical application due to necessity of a film forming technique with a high level. Therefore, sufficient characteristics can not be obtained currently. [0011] As described above, though development of a novel magnetic sensor utilizing a resonant magneto-resistance effect has been gone ahead in order to solve the problem about the magnetic white noise adversely affecting the high density magnetic recording, sufficient characteristics for solving the problem have not been achieved yet. SUMMARY OF THE INVENTION [0012] The present invention has been made in view of the above circumstances, and an object thereof is to provide a resonant magneto-resistance effect element which can suppress magnetic white noises as far as possible. [0013] A resonant magneto-resistance effect element according to a first aspect of the present invention includes: a first magnetic film whose magnetization direction is substantially parallel to a film plane; a second magnetic film whose magnetization direction is substantially perpendicular to the film plane, and a first non-magnetic film which is provided between the first and second magnetic films. [0014] A resonant magneto-resistance effect element according to a second aspect of the present invention includes: a first and second magnetic films whose magnetization directions are substantially parallel to a film plane, and a stacked layer, the stacked layer being provided between the first and second magnetic films, the stacked layer comprising a plurality of sets of a third magnetic film whose magnetization direction is substantially perpendicular to the film plane and a non-magnetic film. [0015] A magnetic head according to a third aspect of the present invention includes: a resonant magneto-resistance effect element above-mentioned as a reproducing element. [0016] A magnetic recording and reproducing apparatus according to a fourth aspect of the present invention includes: a magnetic head above-mentioned. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a sectional view showing a resonant magneto-resistance effect element according to a first embodiment of the present invention; [0018] FIG. 2A is a graph illustratively showing a power spectrum S.sub.<mt> of thermal fluctuation in a ferromagnetic layer; [0019] FIG. 2B is a diagram showing a magnetization component in a film plane of the ferromagnetic layer; [0020] FIG. 3 is a graph showing a device characteristic of the resonant magneto-resistance effect element according to the first embodiment; Continue reading... Full patent description for Magnetic oscillator, magnetic head, and magnetic recording and reproducing apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Magnetic oscillator, magnetic head, and magnetic recording and reproducing apparatus patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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