3results about How to "Improve recording density" patented technology

Embodiments of the invention provide a write head for perpendicular recording in which the magnetic field intensity applied at a read element is reduced with larger write-field gradients and the distance between a write element and a read element is small. In one embodiment, a pair of magnetic bodies for shielding a read element are provided on the leading and trailing sides of the read element respectively and whichever one of the two shields is the longer in the length from the air bearing surface is shorter than the length up to the back contact position PBK at which a main pole and an auxiliary pole are connected.

This invention discloses an optical disc and an optical disc device. The optical disc includes a groove bottom channel and a groove top channel formed by spiral grooves. Both the groove bottom channel and the groove top channel have a plurality of recording blocks capable of recording data. Each recording block contains a predetermined number of frames, and each frame has a frame synchronization field of length T at a predetermined position. In adjacent groove bottom channels and groove top channels along the radial direction of the optical disc, the recording block in the groove bottom channel is the first recording block, and the recording block in the groove top channel is the second recording block. The first recording block and the second recording block are offset from each other by an angular offset length along the circumference of the optical disc. The optical disc disclosed in this invention has the advantages of a small reading signal amplitude during optical disc reading, thus eliminating the need for a large dynamic range and very high SNR performance in the reading signal processing circuit, thereby simplifying the implementation of the reading signal processing circuit.

The present invention provides hexagonal ferrite magnetic powder which is extremely useful in achieving both an increase in recording density and an increase in SNR of a magnetic recording medium, is crystalline and has a high saturation magnetization. The hexagonal ferrite magnetic powder contains Bi in a range of a Bi / Fe molar ratio of 0.035 or less, has a saturation magnetization σs of 42.0 Am 2 / kg or more, and a Dx volume of 1800 nm 3 or less, based on a microcrystal diameter. The magnetic powder can be produced by a method for producing hexagonal ferrite magnetic powder, comprising a process of immersing hexagonal ferrite magnetic powder containing Bi in a solution in which a compound X that forms a complex with Bi is dissolved, thereby performing a treatment of dissolving a part of the Bi present in the hexagonal ferrite magnetic powder into the solution.