# US 10,504,543 B1 · Magnetic disk device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,504,543 B1 - Document ID: US10504543B1 - Status: Granted - Kind: B1 - Application number: 16/247,821 - Filed: 2019-01-15 - Granted: 2019-12-10 - Earliest claimed: 2018-08-24 - Assignees: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation - Applicants: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation - Inventors: Gaku Koizumi - Web page: https://patentgrep.com/patent/US10504543B1 ## CPC - G11B 5/1278: {specially adapted for magnetisations perpendicular to the surface of the record carrier} - G11B 5/3133: {including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure (G11B5/3106 takes precedence)} - G11B 5/315: {Shield layers on both sides of the main pole, e.g. in perpendicular magnetic heads} - G11B 5/3116: {Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks (G11B5/3113, G11B5/245 take precedence)} - G11B 2005/0005: {Arrangements, methods or circuits} - G11B 2005/0008: {Magnetic conditionning of heads, e.g. biasing} - G11B 2005/0029: {using magnetisation components of the recording layer disposed mainly perpendicularly to the record carrier surface} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract According to one embodiment, a magnetic disk device includes a magnetic disk, a recording head and a controller configured to control the recording head. The recording head includes a high-frequency oscillator disposed in a write gap formed between a main magnetic pole and a return magnetic pole, and a bias voltage application circuit configured to apply a bias voltage to the high-frequency oscillator. The controller includes a bias voltage controller configured to change a bias voltage to be applied to the high-frequency oscillator in accordance with a sampling frequency of data before the data is recorded on the magnetic disk by the recording head. ## Claims ### Claim 1 A magnetic disk device comprising: a magnetic disk including a recording layer; a recording head configured to apply a recording magnetic field to the recording layer; and a controller configured to control the recording head, wherein the recording head includes: a main magnetic pole configured to generate the recording magnetic field; a return magnetic pole opposed to a tip portion of the main magnetic pole with a write gap therebetween and configured to form a magnetic circuit together with the main magnetic pole by returning magnetic flux from the main magnetic pole; a recording coil configured to excite magnetic flux in a magnetic circuit formed by the main magnetic pole and the return magnetic pole; a high-frequency oscillator disposed in the write gap; and a bias voltage application circuit configured to apply a bias voltage to the high-frequency oscillator through the main magnetic pole and the return magnetic pole, and the controller includes a bias voltage controller configured to change a bias voltage to be applied to the high-frequency oscillator in accordance with a sampling frequency of data before the data is recorded on the magnetic disk by the recording head. ### Claim 2 (depends on 1) The magnetic disk device of claim 1, wherein the bias voltage controller controls the bias voltage to lower relative to a reference bias as the sampling frequency increases. ### Claim 3 (depends on 1) The magnetic disk device of claim 1, wherein the bias voltage controller controls the bias voltage to lower relative to a reference bias or turn off when the sampling frequency is a voltage switching threshold value or higher. ### Claim 4 (depends on 3) The magnetic disk device of claim 3, wherein the bias voltage controller sets the voltage switching threshold value to 1880 MHz or higher and 3230 MHz or lower. ### Claim 5 (depends on 1) The magnetic disk device of claim 1, wherein: the controller further includes a bias polarity controller configured to control polarity of a bias voltage to be applied to the high-frequency oscillator in accordance with a sampling frequency of data when the data is recorded on the magnetic disk by the recording head; and the bias polarity controller switches energizing polarity of the bias voltage to polarity opposite to a direction in which the high-frequency oscillator oscillates when the sampling frequency is a polarity switching threshold value or higher. ### Claim 6 (depends on 5) The magnetic disk device of claim 5, wherein the bias polarity controller sets the polarity switching threshold value to 1880 MHz or higher and 3230 MHz or lower. ### Claim 7 (depends on 1) The magnetic disk device of claim 1, wherein the controller further includes a recording current controller configured to control recording current to be supplied to the recording coil in accordance with a sampling frequency of data when the data is recorded on the magnetic disk by the recording head. ### Claim 8 (depends on 7) The magnetic disk device of claim 7, wherein the recording current controller controls the recording current to lower peak intensity of the recording current as the sampling frequency increases. ### Claim 9 (depends on 7) The magnetic disk device of claim 7, wherein the recording current controller controls the recording current to lengthen rise time of the recording current as the sampling frequency increases. ### Claim 10 (depends on 7) The magnetic disk device of claim 7, wherein: the bias voltage controller controls the bias voltage to lower relative to a reference bias as the sampling frequency increases; and the recording current controller controls the recording current to lower peak intensity of the recording current relative to peak intensity of a reference recording current as the sampling frequency increases. ### Claim 11 A magnetic disk device comprising: a magnetic disk including a recording layer; a recording head configured to apply a recording magnetic field to the recording layer; and a controller configured to control the recording head, wherein the recording head includes: a main magnetic pole configured to generate the recording magnetic field; a return magnetic pole opposed to a tip portion of the main magnetic pole with a write gap therebetween and configured to form a magnetic circuit together with the main magnetic pole by returning magnetic flux from the main magnetic pole; a recording coil configured to excite magnetic flux in the magnetic circuit formed by the main magnetic pole and the return magnetic pole; a high-frequency oscillator disposed in the write gap; and a bias voltage application circuit configured to apply a bias voltage to the high-frequency oscillator through the main magnetic pole and the return magnetic pole, and the controller includes a bias voltage controller configured to change the bias voltage in accordance with a radial position of the magnetic disk on which data is recorded, before the data is recorded on the magnetic disk by the recording head. ### Claim 12 (depends on 11) The magnetic disk device of claim 11, wherein the bias voltage controller controls the bias voltage to lower relative to a reference bias as the radial position of the magnetic disk on which the data is recorded is made closer to an outer circumference. ### Claim 13 (depends on 11) The magnetic disk device of claim 11, wherein the bias voltage controller controls the bias voltage to lower relative to a reference bias or turn off when the radial position of the magnetic disk on which the data is recorded is outside a voltage switching position. ### Claim 14 (depends on 13) The magnetic disk device of claim 13, wherein the bias voltage controller sets the voltage switching position to fall within an area corresponding to a radius of 27 mm or larger and 54 mm or smaller of the magnetic disk. ### Claim 15 (depends on 11) The magnetic disk device of claim 11, wherein: the controller further includes a bias polarity controller configured to control polarity of a bias voltage to be applied to the high-frequency oscillator in accordance with in accordance with the radial position of the magnetic disk on which data is recorded, when the data is recorded on the magnetic disk by the recording head; and the bias polarity controller switches energizing polarity of the bias voltage to polarity opposite to a direction in which the high-frequency oscillator oscillates when the radial position of the magnetic disk on which data is recorded is outside a polarity switching position. ### Claim 16 (depends on 11) The magnetic disk device of claim 11, wherein the bias polarity controller sets the polarity switching position to 27 mm or larger and 54 mm or smaller of a radius of the magnetic disk. ### Claim 17 (depends on 11) The magnetic disk device of claim 11, wherein the controller further includes a recording current controller configured to control recording current to be supplied to the recording coil in accordance with the radial position of the magnetic disk on which the data is recorded, when the data is recorded on the magnetic disk by the recording head. ### Claim 18 (depends on 17) The magnetic disk device of claim 17, wherein the recording current controller controls the recording current to lower peak intensity of the recording current as the radial position of the magnetic disk on which the data is recorded is made closer to an outer circumference. ### Claim 19 (depends on 17) The magnetic disk device of claim 17, wherein the recording current controller controls the recording current to lengthen rise time of the recording current as the radial position of the magnetic disk on which the data is recorded is made closer to an outer circumference. ### Claim 20 (depends on 17) The magnetic disk device of claim 17, wherein: the bias voltage controller controls the bias voltage to lower relative to a reference bias as the radial position of the magnetic disk on which the data is recorded is made closer to an outer circumference; and the recording current controller controls the recording current to lower peak intensity of the recording current relative to peak intensity of a reference recording current as the radial position of the magnetic disk on which the data is recorded is made closer to an outer circumference.