System comprising a magnetic head and a movable magnetic information carrier

Abstract: System comprising a magnetic head (1) and a magnetic information carrier (2), which cooperate with each other through a layer (3) wiih soft magnetic and lubricating properties. The layer (3) is anisotropic, the relative permeability (µx) of the layer, taken in a direction parallel to the head face (2), being less than the relative permeability (µy) of the layer in a direction perpendicular to the head face (9). By using the said layer in systems in which a certain distance between the magnetic head (1) and the information carrier (2) is desirable, the magnetic resistance is reduced and the signal-to-­ noise ratio is improved. The layer (3) may be present on both the magnetic head (1) and on the information carrier (2) as well as on both of them.

Description: The invention relates to a system comprising a magnetic head and a movable information carrier, which through a soft magnetic layer cooperate with each other, the magnetic head being provided with a transducing gap and a head face located opposite a plane of the information carrier. Such a system is disclosed in the United States patent 3,432,837. Therein, the magnetic layer has one face located on the head face and the other plane is in contact with a magnetic tape. Because of the presence of the magnetic layer wear of the magnetic head and the information carrier is reduced. A disadvantage of the prior art system is that a portion of the magnetic flux withdrawn is fed back again to the magnetic tape via a short-circuit path, as a result of which the signal-to-noise ratio is not optimal. An object of the invention is to improve the system defined in the opening paragraph to such an extend that the signal-to-noise ratio is significantly improved. To this end, the system according to the invention is characterized, in that the soft magnetic layer has lubricating properties and is anisotropic, in which the relative permeability (µx) of the layer in a direction at least substantially parallel to the head face and in the direction at least substantially parallel to the head face and in the direction of travel of the information carrier is less than the relative permeability (µy) of the layer in a direction at least substantially perpendicular to the head face. This means inter alia that the magnetic resistance in the said layer in a direction perpendicular to the head face of the magnetic head is less than the magnetic resistance perpendicular to the direction of travel of the information carrier. Consequently, also the magnetic resistance between the information carrier and the magnetic head is smaller than the resistance in the direction of travel perpendicular thereto, preventing further leakage flux losses, so that flux originating from the information carrier flows through the magnetic head. An embodiment of the system according to the invention is characterized in that, the soft-magnetic layer is a layer having properties similar to those of a liquid. The soft-magnetic layer with lubricating properties may be a solid state layer or a layer having properties similar to those of a liquid. If it is a solid state layer, which includes for example iron oxide particles, the layer can be applied by sputtering. If it is a layer having properties similar to those of a liquid, the layer can, for example, be formed by iron oxide particles dispersed in oil or water. In the latter case the layer is usually required to be only in contact with one of the said faces of the magnetic head and the information carrier. Should the layer be in contact with both faces, the layer might deform due to the relative movement of the faces with respect to each other, because of which the anisotropy might get lost. The invention will now be described in greater detail by way of example, with reference to an embodiment shown in the accompanying drawings. Herein: Fig. 1 shows an embodiment of the system according to the invention, and Fig. 2 is a graphic representation of the curve of the magnetic flux between the magnetic head and the information carrier. Fig. 1 shows a system according to the invention comprising a magnetic head 1 and a magnetic information carrier movable in a direction x, which is positioned at a distance d from the magnetic head. The magnetic head comprises two core limbs 7, 8 and is provided with a transducing gap 4, a head face 9 and a winding aperture 5. A coil 6 is wrapped around core limb 7. Between the magnetic head and the information carrier a layer 3, with soft magnetic and lubricating properties, is located. This layer may be made of a solid substance or a liquid substance. An example of a suitable substance is oil or water, in which iron particles are dispersed. In this embodiment layer 3 is located on the magnetic head 1 and a layer of air is present between the layer 3 and the information carrier 2. The magnetic flux, which during reading flows from the information carrier, senses as it were the layer 3, because of which less leakage flux will occur in the thin layer of air still present between the information carrier 2 and the layer 3 (see Fig. 2) and more flux will be transferred to the layer 3. The flux subsequently flows into the magnetic head, which is manufactured from a material, for example MnZn-ferrite, sendust (FeSiAl), permalloy (NiFe), with a still higher permeability than the permeability of the layer 3. In Fig. 2, y indicates the distance to the magnetic head 1. The broken line indicates the flux ⊘ for the case in which no layer is present. The solid line indicates the flux ⊘ for the case in which the layer is located on the magnetic head 1. It is of course also possible to apply the soft magnetic layer with lubricating properties on the plane of the information carrier facing the magnetic head. The most advantageous effect is obtained when the layer fills the whole space between the magnetic head and the information carrier. In this case less flux is short-circuited in the inner parts of the information carrier and thus more flux reaches the space between the information carrier and the magnetic head. Herein the soft magnetic layer may be deposited either fully on the information carrier or fully on the head face of the magnetic head or on both. If layer 3 is an anisotropic layer in which the permeability µy (see Fig. 1) exceeds the permeability µx, then the resistance which the flux meets while flowing from the information carrier to the magnetic head will be reduced even further as regards the resistance which the flux meets in a direction perpendicular to this direction. The system described in the foregoing, in which the magnetic head is not in contact during operation with the information carrier, is especially applied in recording systems utilizing a hard magnetic disc as the information carrier. In such systems the magnetic disc is driven rotationally, and the magnetic head is moved in a radial direction relative to the rotating disc. However, the system according to the invention is also applicable in recording systems in which the magnetic head is in contact with the information carrier. The magnetic head, in the example given an inductive head, may also be structured as a magneto-resistant head.

Claims: A system comprising a magnetic head (1) and a movable magnetic information carrier (2), which through a soft magnetic layer (3) cooperate with each other, the magnetic head being provided with a transducing gap (4) and a head face (9) located opposite a plane of the information carrier, characterized in that the soft magnetic layer (3) has lubricating properties and is anisotropic, in which the relative permeability (µx) of the layer in a direction at least substantially parallel to the head face (9) and in the direction of travel (x) of the information carrier, is less than the relative permeability (µy) of the layer in a direction at least substantially perpendicular to the head face. A system as claimed in Claim 1, characterized in that the soft magnetic layer (3) is a layer having properties similar to those of a liquid. A system as claimed in Claim 1, characterized in that the soft magnetic layer (3) is a solid state layer.

Inventors: RUIGROK JACOBUS JOSEPHUS MARIA, RUIGROK, JACOBUS JOSEPHUS MARIA
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1989
Main classification: G11B5
IPC codes: G11B5