Microwave-assisted magnetic recording (MAMR) head employing advanced current control to establish a magnetic resonance state

• US 9,007,723 B1
• Filed: 12/13/2013
• Issued: 04/14/2015
• Est. Priority Date: 12/13/2013
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Inventors: Igarashi, Masukazu, Shiimoto, Masato, Matsubara, Masato, Sato, Yo, Sugiura, Kenji
• Primary Examiner(s): Klimowicz, Will J
• Application Number:
  US14/106,390
• Time in Patent Office: 487 Days
• Field of Search: 360/125.3, 360/128, 360/31
• US Class Current: 360/125.3
• CPC Class Codes: G11B 2005/0024 Microwave assisted recording
• CPC Class Codes: G11B 5/314 where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers G11B5/3196 takes precedence

Abstract

In one embodiment, a microwave-assisted magnetic recording (MAMR) head includes a main pole configured to write data to a magnetic medium using a write magnetic field, a write coil, wherein the write magnetic field is produced by the main pole upon a recording current, I_w, being provided to the write coil, and a spin torque oscillator (STO) positioned near the main pole, the STO being configured to provide a high-frequency assistance magnetic field to the magnetic medium upon a STO drive current, I_STO, being provided to the STO, wherein the STO drive current, I_STO, is ramped-up prior to the recording current, I_w, being provided to the write coil in order to begin a write operation for writing data to the magnetic medium. A method of operation for the MAMR head and an apparatus including the MAMR head are also described according to additional embodiments.

Claims

1. A magnetic data storage system, comprising:

a microwave-assisted magnetic recording (MAMR) head; and

a controller electrically coupled to the MAMR head for controlling operation of the MAMR head,

wherein the MAMR head comprises;

a main pole configured to write data to a magnetic medium using a write magnetic field;

a write coil, wherein the write magnetic field is produced by the main pole upon a recording current, I_w, being provided to the write coil; and

a spin torque oscillator (STO) positioned near the main pole, the STO being configured to provide a high-frequency assistance magnetic field to the magnetic medium upon a STO drive current, I_STO, being provided to the STO, and

wherein the controller is configured to;

determine a test signal to provide to the MAMR head to determine optimum recording conditions for the MAMR head and the magnetic medium, wherein the predetermined test signal omits current combinations where no STO oscillation occurs;

determine the optimum recording conditions for the MAMR head and the magnetic medium prior to performing a write operation based on alteration of I_STO and I_w via writing to the magnetic medium and subsequent reading from the magnetic medium of the predetermined test signal; and

ramp-up the STO drive current, I_STO, prior to providing the recording current, I_w, to the write coil in order to begin the write operation for writing data to the magnetic medium.

2. The magnetic data storage system as recited in claim 1, wherein the controller is further configured to ramp-down the recording current, I_w, prior to reducing the STO drive current, I_STO, in order to cease the write operation for writing data to the magnetic medium.

3. The magnetic data storage system as recited in claim 1, further comprising:

the magnetic medium; and

a drive mechanism for passing the magnetic medium over the MAMR head.

4. The magnetic data storage system as recited in claim 1, wherein the test signal is determined to avoid current combinations of values of I_w and I_STO that occur in a hysteresis zone in which no STO oscillation occurs after the STO drive current, I_STO, is increased from a region of no STO oscillation.

5. The magnetic data storage system as recited in claim 4, wherein the controller is further configured to ensure that substantially no stoppage of STO oscillation occurs during testing performed using the predetermined test signal.

6. The magnetic data storage system as recited in claim 5, wherein the controller is further configured to create and store a parameter control table which describes a STO non-oscillation region corresponding to a combination of values of I_w and I_STO for which, compared to use of a recording current alone, no gain is able to be produced.

7. The magnetic data storage system as recited in claim 1, wherein the controller is further configured to change the I_STO from a larger value to a smaller value with respect to an I_w set value, and/or to change the I_STO from a smaller value to a larger value with respect to the I_w set value, to determine optimum recording conditions.

8. The magnetic data storage system as recited in claim 7, wherein determining optimum recording conditions for the MAMR head, using a controller of a magnetic data storage system, based on alteration of I_STO and I_w via writing to the magnetic medium and subsequent reading from the magnetic medium of a predetermined test signal the controller is further configured to pause for a period of time without altering the I_w set value when the current provided to the STO is at an I_STO maximum value to allow writing to continue when STO oscillation stops.

9. The magnetic data storage system as recited in claim 1, wherein the controller is further configured to change the I_w from a larger value to a smaller value with respect to an I_STO set value to determine the optimum recording conditions, and/or to change the I_w from a smaller value to a larger value with respect to the I_STO set value to determine the optimum recording conditions.

10. The magnetic data storage system as recited in claim 9, wherein the controller is further configured to pause for a period of time without altering the I_STO set value when the current provided to the write coil is at an I_w minimum value to allow writing to continue when STO oscillation stops.

11. The magnetic data storage system as recited in claim 1, wherein the controller is further configured to determine the optimum recording conditions based on a comparison with a measurement value of I_STO=0.

12. A method for using a microwave-assisted magnetic recording (MAMR) head, the method comprising:

determining, using a controller of a magnetic data storage system, a test signal to provide to the MAMR head to determine optimum recording conditions for the MAMR head and a magnetic medium, wherein the predetermined test signal omits current combinations where no spin torque oscillator (STO) oscillation occurs;

determining, using the controller, optimum recording conditions for the MAMR head and the magnetic medium prior to performing a write operation based on alteration of a STO drive current, I_STO, and a recording current, I_w, via writing to the magnetic medium and subsequent reading from the magnetic medium of the predetermined test signal;

energizing the STO positioned near a main pole of the MAMR head to provide a high-frequency assistance magnetic field by providing the STO drive current, I_STO, to the STO; and

energizing a write coil to produce a write magnetic field via the main pole by providing the recording current, I_w, to the write coil after waiting for a predetermined time delay such that the STO drive current, I_STO, is ramped-up prior to the recording current, I_w, being provided to the write coil in order to begin the write operation for writing data to the magnetic medium.

13. The method as recited in claim 12, further comprising ramping-down the recording current, I_w, using the controller, prior to reducing the STO drive current, I_STO, in order to cease the write operation for writing data to the magnetic medium.

14. The method as recited in claim 12, wherein the determining the test signal comprises avoiding adding current combinations of values of I_w and I_STO to the test signal that occur in a hysteresis zone in which no STO oscillation occurs after the STO drive current, I_STO, is increased from a region of no STO oscillation.

15. The method as recited in claim 12, further comprising:

changing the I_STO from a larger value to a smaller value with respect to an I_w set value, and/or to change the I_STO from a smaller value to a larger value with respect to the I_w set value, to determine optimum recording conditions; and

pausing for a period of time without altering the I_w set value when the current provided to the STO is at an I_STO maximum value to allow writing to continue when STO oscillation stops.

16. The method as recited in claim 12, further comprising:

changing the I_w from a larger value to a smaller value with respect to an I_STO set value, and/or to change the I_w from a smaller value to a larger value with respect to the I_STO set value to determine optimum recording conditions; and

pausing for a period of time without altering the I_STO set value when the current provided to the write coil is at an I_w minimum value to allow writing to continue when STO oscillation stops.

17. The method as recited in claim 12, further comprising ensuring that substantially no STO oscillation stoppage occurs during testing performed using the predetermined test signal.

18. The method as recited in claim 12, further comprising creating and storing, using the controller, a parameter control table which describes a STO non-oscillation region corresponding to a combination of values of I_w and I_STO for which, compared to use of a recording current alone, no gain is able to be produced.

19. The method as recited in claim 12, further comprising determining the optimum recording conditions, using the controller, based on a comparison with a measurement value of I_STO=0.

20. An apparatus, comprising:

at least one microwave-assisted magnetic recording (MAMR) head, each MAMR head comprising;

a main pole configured to write data to a magnetic medium using a write magnetic field;

a write coil, wherein the write magnetic field is produced by the main pole upon a recording current, I_w, being provided to the write coil; and

a spin torque oscillator (STO) positioned near the main pole, the STO being configured to provide a high-frequency assistance magnetic field to the magnetic medium upon a STO drive current, I_STO, being provided to the STO;

the magnetic medium;

a drive mechanism for passing the magnetic medium over the at least one MAMR head; and

a controller electrically coupled to the at least one MAMR head for controlling operation of the at least one MAMR head, the controller being configured to;

provide the STO drive current, I_STO, to the STO to provide the high-frequency assistance magnetic field;

provide the recording current, I_w, to the write coil to produce the write magnetic field via the main pole;

determine a test signal to provide to the at least one MAMR head to determine optimum recording conditions for the at least one MAMR head and the magnetic medium, wherein the predetermined test signal omits current combinations where no STO oscillation occurs;

determine the optimum recording conditions for the MAMR head prior to performing a write operation based on alteration of I_STO and I_w via writing to the magnetic medium and subsequent reading from the magnetic medium of the predetermined test signal;

ramp-up the STO drive current, I_STO, prior to providing the recording current, I_w, to the write coil in order to begin the write operation for writing data to the magnetic medium; and

ramp-down the recording current, I_w, prior to reducing the STO drive current, I_STO, in order to cease the write operation for writing data to the magnetic medium.