Abstract: A sintered material for recording/reading (particularly magnetic) head slider is produced by:preparing a powdery mixture which comprises 0.5 to 6.0% by weight of at least one component selected from the component group A consisting of the following elements and compounds thereof, a garnet type compound consisting essentially of erbium oxide and aluminum oxide in amounts of 2 to 12% by weight and 0 (exclusive) to 2 (inclusive) % by weight based on the total composition, respectively, and expressed by the formula Er.sub.3 (Al,Er).sub.2 (AlO.sub.4).sub.3 through (Er, Al).sub.3 Al.sub.2 (AlO.sub.4).sub.3, and the balance being silicon carbide powder:the elements for the component group A being Ti, V, Cr, Mn, Mg, Y, Zr, Nb, Mo, Ba, La, Ce, Gd, Hf, Ta, W, Th, and Cs; andsintering the resultant mass under the application of a high pressure.Further sintering aids of Be, BeO, B and B.sub.4 C may be present. For the garnet type compound, erbium oxide may be used, preferably in combination with alumina.

Abstract: A grooved magnetic substrate including an alumina film layer having a Knopp hardness of 600 kg/mm.sup.2 to 1200 kg/mm.sup.2 charged in at least one groove formed in a surface of a magnetic substrate. The magnetic substrate may be Mn-Zn or Ni--Zn base ferrite. The alumina film layer is formed by sputtering.

Abstract: A sintered material for recording/reading (particularly magnetic) head slider is produced by:preparing a powdery mixture which comprises 0.5 to 6.0% by weight of at least one component selected from the component group A consisting of the following elements and compounds thereof, a garnet type compound consisting essentially of erbium oxide and aluminum oxide in amounts of 2 to 12% by weight and 0 (exclusive) to 2 (inclusive) % by weight based on the total composition, respectively, and expressed by the formula Er.sub.3 (Al,Er).sub.2 (AlO.sub.4).sub.3 through (Er,Al).sub.3 Al.sub.2 (AlO.sub.4).sub.3, and the balance being silicon carbide powder:the elements for the component group A being Ti, V, Cr, Mn, Mg, Y, Zr, Nb, Mo, Ba, La, Ce, Gd, Hf, Ta, W, Th, and Cs; andsintering the resultant mass under the application of a high pressure.Further sintering aids of Be, BeO, B and B.sub.4 C may be present. For the garnet type compound, erbium oxide may be used, preferably in combination with alumina.

Abstract: An improved magnetic recording disc comprising: a substrate member of an alumina-based ceramic material having micropores of 5 .mu.m or below and having a relative theoretical density of 90% or higher; a glass coating layer of a thickness of 3 to 200 .mu.m with a surface roughness (R.sub.z) of 180 angstroms or below, and being free from micropores and strain; a magnetic thin film formed on the surface of the glass coating layer; and a protective film formed thereon.A process for production of the magnetic recording disc comprises: forming a glass coating layer to a thickness of 5 to 220 .mu.m on the surface of an alumina-based ceramic substrate having micropores of 5 .mu.m or below and a relative theoretical density of at least 90%; then subjecting the glass coating layer to mechanochemical polishing to a layer thickness of 3 to 200 .mu.m, to make free from micropores and strain, and to have a surface roughness (R.sub.

Abstract: A grooved magnetic substrate including an alumina film layer having a Knoop hardness of 600 kg/mm.sup.2 to 1200 kg/mm.sup.2 charged in at least one groove formed in a surface of a magnetic substrate. The magnetic substrate may be Mn-Zn or NiZn base ferrite. The alumina film layer is formed by sputtering.

Abstract: A substrate member for recording disk characterized in that a glass coating film is provided on an alumina base ceramic material having micropores of no larger than 5 microns and a relative theoretical density of no less than 96%, said glass coating film having a surface roughness of no more than 80 angstroms, being substantially pore-free and strain-free on the surface, and having a thickness of 0.3 to 200 microns and a relative difference of no more than 10.sup.-6 /deg in the coefficient of thermal expansion with respect to said base material.

Abstract: A substrate member for recording disks comprises a sputtered film of Al.sub.2 O.sub.3, SiO.sub.2 and/or Si.sub.3 N.sub.4 on the surface of an alumina base ceramic material having therein micropores of no more than 5 microns and a relative theoretical density of no less than 96% said sputtered film having a surface roughness of no more than 80 angstroms, being substantially pore-free and strain-free on the surface, and having a thickness of 0.3 to 30 microns.

Abstract: A composite substrate for a thin-film magnetic head comprises a substrate material, and an insulating oxide film formed thereon, and defining a smooth and stress-free surface having a surface roughness not greater than 50 .ANG.. A film of a magnetic material having improved magnetic properties may be formed on the surface of the oxide film.