# US 10,482,912 B1 · Microwave-assisted magnetic recording apparatus and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,482,912 B1 - Document ID: US10482912B1 - Status: Granted - Kind: B1 - Application number: 16/249,438 - Filed: 2019-01-16 - Granted: 2019-11-19 - Earliest claimed: 2018-06-20 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Xiong Liu; Lihong Zhang; PengBoon Khoo - Web page: https://patentgrep.com/patent/US10482912B1 ## CPC - G11B 5/59688: {Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns} - G11B 5/674: {having differing macroscopic or microscopic structures, e.g. differing crystalline lattices, varying atomic structures or differing roughnesses} - G11B 20/10009: {Improvement or modification of read or write signals} - G11B 20/10046: {filtering or equalising, e.g. setting the tap weights of an FIR filter} - G11B 20/1217: {on discs} - G11B 2005/0024: {Microwave assisted recording} - 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 A magnetic recording medium includes a recording surface comprising a first recording layer having a first ferromagnetic resonant frequency and a second recording layer having a second ferromagnetic resonant frequency. The first recording layer is configured for storing user data and the second recording layer configured for storing servo data. A recording head arrangement is configured for microwave-assisted magnetic recording (MAMR) and writing user data to the first recording layer. The recording head arrangement comprises a write pole configured to generate a write magnetic field, and a write-assist arrangement proximate the write pole. The write-assist arrangement is configured to generate a radiofrequency assist magnetic field at a frequency that corresponds to the first ferromagnetic resonant frequency. A reader of the recording head arrangement is configured to read combined signals from the first and second recording layers. ## Claims ### Claim 1 An apparatus, comprising: a magnetic recording medium having a recording surface comprising a plurality of recording layers each having a different ferromagnetic resonant frequency; and a recording head arrangement configured for microwave-assisted magnetic recording (MAMR) and writing user data to a first recording layer of the plurality of recording layers, the recording head arrangement comprising: a write pole configured to generate a write magnetic field; and a write-assist arrangement proximate the write pole, the write-assist arrangement configured to generate a radiofrequency assist magnetic field at a frequency that corresponds to a first ferromagnetic resonant frequency of the first recording layer. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the first recording layer is devoid of servo data. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the plurality of recording layers comprises a second recording layer having a second ferromagnetic resonant frequency different from the first ferromagnetic resonant frequency. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the second recording layer is configured to store servo data. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein the first recording layer is situated above the second recording layer on the recording surface. ### Claim 6 (depends on 4) The apparatus of claim 4, wherein the first recording layer is situated below the second recording layer on the recording surface. ### Claim 7 (depends on 1) The apparatus of claim 1, comprising a reader configured to read combined signals from the plurality of recording layers. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein: the plurality of recording layers comprises a second recording layer having a second ferromagnetic resonant frequency different from the first ferromagnetic resonant frequency, the second recording layer configured to store servo data; the reader is coupled to a channel; and the channel comprises: a first filter coupled to a decoder, the first filter configured to separate a user data signal from the combined signals; and a second filter coupled to a servo demodulator, the second filter configured to separate a servo data signal from the combined signals. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the first filter comprises a high pass filter and the second filter comprises a low pass filter. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the magnetic recording medium is configured for perpendicular magnetic recording. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the magnetic recording medium is configured for bit patterned magnetic recording. ### Claim 12 An apparatus, comprising: a magnetic recording medium comprising: a first recording surface comprising a plurality of recording layers each having a different ferromagnetic resonant frequency; and a second recording surface comprising a plurality of recording layers each having a different ferromagnetic resonant frequency; a first recording head arrangement configured for microwave-assisted magnetic recording (MAMR) and writing user data to a first recording layer of the plurality of recording layers of the first recording surface, the first recording head arrangement comprising: a first write pole configured to generate a write magnetic field; and a first write-assist arrangement proximate the first write pole, the first write-assist arrangement configured to generate a radiofrequency assist magnetic field at a frequency that corresponds to a ferromagnetic resonant frequency of the first recording layer; and a second recording head arrangement configured for MAMR and writing user data to a second recording layer of the plurality of recording layers of the second recording surface, the second recording head arrangement comprising: a second write pole configured to generate a write magnetic field; and a second write-assist arrangement proximate the second write pole, the second write-assist arrangement configured to generate a radiofrequency assist magnetic field at a frequency that corresponds to a ferromagnetic resonant frequency of the second recording layer. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the first and second recording layers are devoid of servo data. ### Claim 14 A method, comprising: moving a recording head arrangement configured for microwave-assisted magnetic recording (MAMR) relative to a magnetic recording medium, the magnetic recording medium having a recording surface comprising a plurality of recording layers each having a different ferromagnetic resonant frequency; generating a radiofrequency assist magnetic field having a frequency that corresponds to a first ferromagnetic resonant frequency of a first recording layer of the plurality of recording layers; generating a write field; and writing user data to the first recording layer using the write field and the assist magnetic field. ### Claim 15 (depends on 14) The method of claim 14, wherein the first recording layer is devoid of servo data. ### Claim 16 (depends on 14) The method of claim 14, wherein: the plurality of recording layers comprises a second recording layer having a second ferromagnetic resonant frequency different from the first ferromagnetic resonant frequency; and the second recording layer is configured to store servo data. ### Claim 17 (depends on 14) The method of claim 14, comprising reading combined signals from the plurality of recording layers. ### Claim 18 (depends on 17) The method of claim 17, wherein the plurality of recording layers comprises a second recording layer having a second ferromagnetic resonant frequency different from the first ferromagnetic resonant frequency, the second recording layer configured to store servo data, the method comprising: separating a user data signal from the combined signals; decoding the user data signal and outputting the decoded user data signal; separating a servo data signal from the combined signals; and demodulating the servo data signal. ### Claim 19 (depends on 14) The method of claim 14, wherein the magnetic recording medium is configured for perpendicular magnetic recording. ### Claim 20 (depends on 14) The method of claim 14, wherein the magnetic recording medium is configured for bit patterned magnetic recording.