Thin-film magnetic head

Abstract: A thin-film magnetic head comprises a magnetic, yoke, having a first and a second flux conductor (1, 2) and a magneto-­ resistance element (4) remote from a head face (7). A first edge portion (4a) of the magneto-resistance element (4) is located closer to the head face (7) than a second edge portion (4b). The first flux conductor (1) extends from the head face (7) to close to the first edge portion (4a) and the second flux conductor (2) extends from the head face at least to the second edge portion (4b). Furthermore, the magnetic head includes a further magneto-resistance element (5) which forms part of the magnetic yoke and is located between the first and the second flux conductors (1, 2) at the head face (7).

Description: The invention relates to a thin-film magnetic head having a head face for cooperation with an information carrier, which thin-film magnetic head comprises a magnetic yoke having a first flux conductor and a second flux conductor, both contiguous to the head face, a first magneto-resistance element remote from the head face, a first edge portion of which is closer to the head face than a second edge portion, and a second magneto-resistance element, which second magneto-resistance element extends parallel to the first magneto-resistance element and is located between the first flux conductor and the second flux conductor and magnetically cooperates with the first and second flux conductors during operation, the first and second magneto-resistance elements both extending parallel to the head face and having an axis of easy magnetization extending parallel to the head face, the first flux conductor extending at least to the second edge portion of the first magneto-resistive element. Such a magnetic head is a yoke magneto-resistance head and is extremely suitable for reading long-wave signals of analog information from a track of a magnetic information carrier. JP-A-63-220409 which is reflected in the preamble of claim 1 discloses a yoke magneto-resistance magnetic head having two magneto-resistance elements for reading long-wave and short-wave signals. This construction has the disadvantage that the magneto-resistance element located near the head face and intended to read short-wave signals is located remote from the head face. The element is not so suitable for reading signals having very short wavelengths. In addition to the magnetic head defined in the opening paragraph, shielded magneto-resistance heads are also known, wherein a magneto-resistance element is located at the head face between two flux conductors. Such a magnetic head is extremely suitable for reading short-wave signals representing digital information from a track of a magnetic information carrier. JP-A-59-52425 discloses such a magnetic head. US-A-4,729,048 discloses a magnetic head comprising a shielded magneto-resistance head in addition to a yoke magneto-resistance element. This known magnetic head has the disadvantage that it must be provided with two transducing gaps to be able to read both short-wave and long-wave signals from tracks of a magnetic information carrier. An object of the invention is to provide a simplified structure of a magnetic head, suitable for reading information having both short and long wavelengths. To that end, the invention is characterized, in that the second flux conductor extends to at least the first edge portion of the first magneto-resistive element, the second magneto-resistance element being contiguous to the head face. This provides a magnetic head having one transducing gap and a structure having both a yoke and a shielded magneto-resistance head, so that with one transducing gap signals having both short and long wavelengths can be read optimally. JP-A-56-65329 discloses a magneto-resistance magnetic head for reading long-wave and short-wave signals. This construction has the disadvantage that for the reading of long-wave signals the magnetic flux cannot be passed on to the element remote from the head face, so that long-wave signals cannot be read equally well as in the case of a yoke magneto-resistance head. The structure according to the invention has the advantage that signals of both long and short wavelengths can be read optimally. An embodiment of the thin-film magnetic head according to the invention, is characterized in that the magneto-resistance element and the further magneto-resistance element have each one end interconnected via an electrically conducting connection track, which end coincides with an end of the axis of easy magnetization, and are each connected by means of their other end, which coincides with an other end of the axis of easy magnetization, to electrically conducting connection tracks. By not connecting the magneto-resistance elements individually but by arranging them in series, two electrically conducting connection tracks are saved and furthermore a larger resistance change is measured than in the case where reading is only effected with one of the two magneto-resistance elements. Also the electronic circuit for reading and controlling the magneto-resistance elements can in this case be of a simpler structure than when the magneto-resistance elements are connected individually. Such a connection of two magneto-resistance elements in a yoke magneto-resistance head is disclosed in the Japanese Patent Application JP-A-63-69016. A further embodiment of the thin-film magnetic head according to the invention, is characterized, in that a bias winding extends close to and parallel to at least one of the magneto-resistance heads. By energizing the bias winding it is possible to have the magneto-resistance elements function in their linear measuring range whereby non-linearities may be avoided. The invention will now be described in greater detail by way of example with reference to embodiments of a thin-film magnetic head according to the invention shown in the accompanying Figures. Therein, Fig. 1 is a cross-sectional view of a thin-film magnetic head according to the invention, Fig. 2 is a lay-out of a first variant of the thin-film magnetic head shown in Fig. 1, and Fig. 3 is a lay-out of a second variant of the thin-film magnetic head with series-arranged magneto-resistance elements, shown in Fig. 1. Fig. 1 is a cross-sectional view of an embodiment of the thin-film magnetic head according to the invention. This magnetic head is provided with a head face 7 for cooperation with an information carrier 8 which is movable in the direction of the double arrow 9. The magnetic head includes a substrate 1 of a magnetic material forming a first flux conductor contiguous to the head face 7. Instead of a magnetic substrate it is alternatively possible to start from a non-magnetic substrate on which a magnetic layer is deposited which then functions as the flux conductor. Furthermore, the magnetic head includes a second flux conductor 2 contiguous to the head face and a magneto-resistance element 4. The first and second flux conductors 1, 2 and the magneto-resistance element 4 form part of a magnetic yoke. The second flux conductor 2 extends to a first edge portion 4a of the magneto-resistance element 4 and the substrate 1 extends to beyond a second edge portion 4b of the magneto-resistance element 4. The magnetic head further includes a third flux conductor 3, located at a distance d behind the second flux conductor 2 when seen from the head face 7. This third flux conductor 3 is not essential for the mode of operation of the magnetic head and may optionally be omitted. The distance d between the second and third flux conductors 2, 3 is magnetically bridged by the magneto-resistance element 4. It is alternatively possible to provide this magneto-resistance element 4 on the sides of the second and the third flux conductors facing away from the substrate. A further magneto-resistance element 5 which is contiguous to the head face 7, is present between the first and the second flux conductors 1 and 2. A bias winding 6 for premagnetization of the magneto-resistance element 4 is located between the magneto-resistance element 4 and the substrate 1. Such a conductor can alternatively be deposited between the further magneto-resistance element 5 and the substrate 1. The magneto-resistance elements, flux conductors and the electrical conductor are insulated from each other by insulating material 10. Fig. 2 is a lay-out of a first variation of a pair of the above-described thin-film magnetic heads in accordance with the invention, provided with a plurality of transducing gaps. The axes of easy magnetization 11, 12 of the magneto-resistance elements 4, 5, 13, 14 extend parallel to the head face 7. The pairs of magneto-resistance elements 4, 5 and 13, 14, located between the flux conductors 2, 3, 15, 16 and the substrate 1, are connected to electrically conducting connection tracks 17. Thus, each magneto-resistance element can be individually connected. The continuous bias winding 6 is located between the magneto-resistance elements 4 and 13 and the substrate 1. Fig. 3 is a lay-out of a second variation of the thin-film magnetic head according to the invention, wherein the magneto-resistance elements 4 and 5, located between the second and the third flux conductors 2 and 3 and the substrate 1 are electrically interconnected via an electrically conducting connection track 18 at one end 4c, 5a and are connected at their other end 4d, 5b to electrically conducting connection tracks 17. Thus, the magneto-resistance elements 4 and 5 are arranged in series and voltage fluctuations due to the changes in resistance of the magneto-resistance elements are added together, so that a larger output is possible. It will be obvious that the invention is not limited to the embodiments described in the foregoing. Barber poles may be deposited on the magneto-resistance elements to enlarge the linear operating range and the bias winding may optionally be omitted. A magneto-resistance element having a Barber pole is described in the United States Patent 4,052,748.

Claims: A thin-film magnetic head having a head face (7) for cooperation with an information carrier, which thin-film magnetic head comprises a magnetic yoke having a first flux conductor (1) and a second flux conductor (2), both contiguous to the head face, a first magneto-resistance element (4) remote from the head face, a first edge portion (4a) of which is closer to the head face than a second edge portion (4b), and a second magneto-resistance element (5), which second magneto-resistance element extends parallel to the first magneto-resistance element and is located between the first flux conductor and the second flux conductor and magnetically cooperates with the first and second flux conductors during operation, the first and second magneto-resistance elements both extending parallel to the head face and having an axis of easy magnetization (11, 12) extending parallel to the head face, the first flux conductor extending at least to the second edge portion of the first magneto-resistive element, characterized in that the second flux conductor (2) extends to at least the first edge portion (4a) of the first magneto-resistive element, the second magneto-resistance element (5) being contiguous to the head face (7). A thin-film magnetic head as claimed in Claim 1, characterized in that the first magneto-resistance element (4) and the second magneto-resistance element (5) have each one end interconnected via an electrically conducting connection track (18), which end coincides with an end of the axis of easy magnetization, and are each connected by means of their other end, which coincides with an other end of the axis of easy magnetization, to electrically conducting connection tracks (17). A thin-film magnetic head as claimed in Claim 1 or 2, characterized in that a bias winding (6) extends near to and parallel to at least one of the magneto-resistance elements.

Inventors: SOMERS GERARDUS HENRICUS JOHAN, SOMERS, GERARDUS HENRICUS JOHANNUS
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1990
Main classification: G11B5
IPC codes: G11B5