Abstract: A glass-ceramic has a hexacelsian as a primary crystal phase and is characterized by satisfying a relation of 0≦I(101)/I(110)≦1.5 when a diffraction intensity of (101) face of hexacelsian in an X-ray diffraction is I(101) and a diffraction intensity of (110) face thereof is I(110).

Abstract: A glass-ceramic has a hexacelsian as a primary crystal phase and is characterized by satisfying a relation of 0≦I(101)/I(110)≦1.5 when a diffraction intensity of (101) face of hexacelsian in an X-ray diffraction is I(101) and a diffraction intensity of (110) face thereof is I(110).

Abstract: A magnetic disc substrate is provided, which includes a magnetic disc substrate body made of glass and is characterized in that a metal element capable of absorbing light is present in at least a surface portion of the magnetic disc substrate body, and a texture is formed on a surface of the magnetic disc substrate body. Ions of the metal element are dispersed in the surface portion of the magnetic disc substrate, or the metal element is contained in a composition of the glass constituting the magnetic disc substrate in the form of an oxide. The glass is preferably a crystallized glass a Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 based crystallized glass, which particularly preferably contains 65 to 85 wt % of SiO.sub.2, 8 to 15 wt % of Li.sub.2 O, 2 to 8 wt % of Al.sub.2 O.sub.3, 1 to 5 wt % of P.sub.2 O.sub.5 and 1 to 10 wt % of ZrO.sub.2 and has lithium disilicate (Li.sub.2 O.multidot.2SiO.sub.2) as a main crystalline phase.

Abstract: A magnetic disc substrate is provided, which includes a magnetic disc substrate body made of glass and is characterized in that a metal element capable of absorbing light in at least a surface portion of the magnetic disc substrate body, and a texture is formed on a surface of the magnetic disc substrate body. Ions of the metal element are dispersed in the surface portion of the magnetic disc substrate, or the metal element is contained in a composition of the glass constituting the magnetic disc substrate in the form of an oxide. The glass is preferably a crystallized glass a Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 based crystallized glass, which particularly preferably contains 65 to 85 wt % of SiO.sub.2, 8 to 15 wt % of Li.sub.2 O, 2 to 8 wt % of Al.sub.2 O.sub.3, 1 to 5 wt % of P.sub.2 O.sub.5 and 1 to 10 wt % of ZrO.sub.2 and has lithium disilicate (Li.sub.2 O.2SiO.sub.2) as a main crystalline phase.

Abstract: A process for producing a crystallized glass substrate for magnetic disks, including the steps of: (a) holding an amorphous glass plate having a uniform thickness and two principal flat surfaces thereof between a pair of pressing setters in a sandwiched fashion, which pressing setters are non-reactive with the amorphous glass and undeformable during heating for crystallization of the amorphous glass; (b) softening the amorphous glass plate in a sandwiched stack form by heating at a temperature above an annealing point of the amorphous glass, whereby the principal surfaces are fitted onto the flat surfaces of the pressing setters to rectify warping to flatten the amorphous glass plate; and (c) then, increasing the temperature to a crystal growth temperature to grow crystals within the amorphous glass, whereby the amorphous glass plate is crystallized as maintaining its warp-free state, followed by solidifying.

Abstract: A magnetic head core for a magnetic head including a first and a second ferrite member butted and bonded together to form an annular, closed magnetic path around a coil-winding groove, and a coil attached to a coil-winding portion of the first ferrite member. The first and second ferrite members provide a sliding surface to which a magnetic recording medium is opposed, and which extends across the first and second ferrite members. A non-magnetic material is secured to at least one of an inner surface and an outer surface of the coil-winding portion. The non-magnetic material is located below the sliding surface, and is spaced apart from the magnetic recording medium with the sliding surface disposed between the non-magnetic material and the magnetic recording medium.

Abstract: A composite magnetic head core with a writing/reading track and two erasing tracks, including a first ferrite block, and a second and a third ferrite block bonded to opposite surfaces of the first block interposed therebetween. The opposite abutting surfaces of the first block have respective first and second recessed portions, and a first rectangular protrusion and two second rectangular protrusions which protrude from the first and second recessed portions, respectively. The first protrusion is positioned between the two second protrusions in a direction of width of the writing/reading and erasing tracks. The first protrusion cooperates with the second block, to define a writing/reading magnetic gap of the writing/reading track, while the second protrusions cooperate with the third block, to define two erasing magnetic gaps of the erasing tracks. The first protrusion has a width defining the width of the writing/reading track, and a longitudinal end defining a depth of the writing/reading magnetic gap.

Abstract: A head core slider for a rigid magnetic disk drive, including a slider body, a track portion, a yoke portion and a narrow stepped portion. The slider body has two spaced-apart parallel air bearing portions, and the track portion is formed integrally with at least one of the bearing portions, so as to extend from one end of the bearing portion in the direction of length of the bearing portion. The track portion has the same height as the bearing portion, and a width smaller than that of the bearing portion. The yoke portion is formed integrally with the track portion, so as to extend from one end of the track portion remote from the bearing portion, and has a protrusion of the same height as the track portion. The width of the protrusion is smaller than that of the bearing portion and larger than that of the track portion.

Abstract: A magnetic head slider having an operating surface on which are formed a pair of air-bearing portions extending in a direction of flow of an air stream into a flying height between the head slider and a recording medium, a cross rail extending between the air-bearing portions, and a pressure-reducing portion formed between the air-bearing portions and downstream of the cross rail. The air-bearing portions, cross rail and pressure-reducing portions cooperate to maintain the amount of the flying height at an optimum value. The slider uses a ferrite single crystal which provides at least the operating surface and which have crystal faces oriented such that the (111) plane of the crystal is not a plane which is parallel to the extension of the downstream edge line of the cross rail, or such that the (111) plane is parallel to the extension of the downstream edge line of the cross rail and is inclined at an angle of at least 60.degree. with respect to the operating surface.

Abstract: A magnetic head core having a generally annular structure with an inner coil-winding aperture, and a magnetic gap which has a predetermined width and which is formed so as to extend in a direction across the annulus of the annular structure. The annular structure is formed by a plurality of ferrite core elements bonded together by direct solid-solid reaction bonding, with a non-magnetic layer of SiO or SiO.sub.2 interposed between two opposed portions of the ferrite core elements which define the magnetic gap. The non-magnetic layer defines the width of the magnetic gap.

Abstract: A magnetic head slider having an operating surface on which are formed a pair of air-bearing portions extending in a direction of flow of an air stream into a flying height between the head slider and a recording medium, a cross rail extending between the air-bearing portions, and a pressure-reducing portion formed between the air-bearing portions and downstream of the cross rail. The air-bearing portions, cross rail and pressure-reducing portions cooperate to maintain the amount of the flying height at an optimum value. The slider uses a ferrite single crystal which provides at least the operating surface and which have crystal faces oriented such that the (111) plane of the crystal is not a plane which is parallel to the extension of the downstream edge line of the cross rail, or such that the (111) plane is parallel to the extension of the downstream edge line of the cross rail and is inclined at an angle of at least 60.degree. with respect to the operating surface.

Abstract: A composite magnetic head core with a writing/reading track and two erasing tracks, including a first ferrite block, and a second and a third ferrite block bonded to opposite surfaces of the first block interposed therebetween. The opposite abutting surfaces of the first block have respective first and second recessed portions, and a first rectangular protrusion and two second rectangular protrusions which protrude from the first and second recessed portions, respectively. The first protrusion is positioned between the two second protrusions in a direction of width of the writing/reading and erasing tracks. The first protrusion cooperates with the second block, to define a writing/reading magnetic gap of the writing/reading track, while the second protrusions cooperate with the third block, to define two erasing magnetic gaps of the erasing tracks. The first protrusion has a width defining the width of the writing/reading track, and a longitudinal end defining a depth of the writing/reading magnetic gap.

Abstract: A head core slider for a rigid magnetic disk drive, and a method of producing the same. The core slider includes a slider body, a track portion, a yoke portion and a narrow stepped portion. The slider body has two spaced-apart parallel air bearing portions, and the track portion is formed integrally with at least one of the bearing portions, so as to extend from one end of the bearing portion in the direction of length of the bearing portion. The track portion has the same height as the bearing portion, and a width smaller than that of the bearing portion. The yoke portion is formed integrally with the track portion, so as to extend from one end of the track portion remote from the bearing portion, and has a protrusion of the same height as the track portion. The width of the protrusion is smaller than that of the bearing portion and larger than that of the track portion.

Abstract: A core for magnetic head, which has a groove depth of at least 10 .mu.m with a dimensional accuracy not lower than .+-.2 .mu.m in the groove for defining the track of the core, can be obtained by subjecting a gapped bar made of ferrite and/or Sendust to a laser-induced etching wherein a laser beam having a focused beam diameter of not larger than 50 .mu.m, preferably not larger than 20 .mu.m, and a laser power P in a specified range is irradiated at a scanning speed V that is within a range between 2 .mu.m/sec and 200 .mu.m/sec and delimited by the laser power P, in a phosphoric acid or alkali metal hydroxide aqueous solution.

Abstract: A magnetic head core having a generally annular structure with an inner coil-winding aperture, and a magnetic gap which has a predetermined width and which is formed so as to extend in a direction across the annulus of the annular structure. The annular structure is formed by a plurality of ferrite core elements bonded together by direct solid-solid reaction bonding, with a non-magnetic layer of SiO or SiO.sub.2 interposed between two opposed portions of the ferrite core elements which define the magnetic gap. The non-magnetic layer defines the width of the magnetic gap.

Abstract: A method of producing a magnetic head core slider including integrally formed slider body and yoke portion. The slider body has two parallel air bearing portions, while the yoke portion has a track portion. The slider body and yoke portion cooperatively provide a magnetic gap open in the track portion. The core slider is prepared from an integral ferrite bar consisting of a first and a second ferrite block which give the slider body and the yoke portion, respectively. Track-defining grooves are formed by laser-induced etching in one surface of the bar, such that the grooves extend across the interface of the bonded two blocks. The grooves define the width of the track portion. An etching mask is applied to cover portions of the bar corresponding to the air bearing portions and the track portion. The masked surface of the bar is chemically etched to form the air bearing portions, and a track protrusion including the track portion, such that the air bearing portion and the track protrusion have the same height.

Abstract: A method of forming, on a surface of a Mn-Zn ferrite single crystal, a recessed portion which has a predetermined cross sectional profile and at least one straight ridge each of which defines a boundary in the profile. An etching mask is formed on the surface of the ferrite single crystal, so as to provide the recessed portion by etching such that each straight edge of the profile lies in a (100) or (110) plane of the ferrite single crystal which is perpendicular to the surface on which the etching mask is formed. The ferrite single crystal with the etching mask in exposed to an aqueous solution which substantially consists of water and the balance consisting principally of phosphoric acid, whereby the surface of the ferrite single crystal is chemically etched, so as to produce the recessed portion such that an inclined surface is formed so as to extend parallel to the straight ridge, and such that the straight ridge defines an edge of the inclined surface.