Perpendicular magnetic recording system with auxiliary coil and circuitry for fast switching of write pole magnetization
View Patent ↗A perpendicular magnetic recording system has a write head having a main coil (the write coil) and main pole (the write pole) that directs write flux in a direction perpendicular to the recording layer in the magnetic recording medium, and an auxiliary coil and auxiliary pole that injects magnetic flux into the write pole at an angle to the primary or perpendicular axis of the write pole. The additional flux from the auxiliary pole, which is injected non-parallel to the primary magnetization of the write pole, exerts a relatively large torque on the magnetization of the write pole, thereby facilitating magnetization reversal of the write pole. Electrical circuitry is connected to the main coil and the auxiliary coil to generate the auxiliary flux simultaneous with the switching of the magnetization of the write pole.
1. A perpendicular magnetic recording write system for magnetizing regions in a perpendicular magnetic recording layer comprising:
a write head comprising
a main pole;
a main electrically conductive coil coupled to the main pole for generating magnetic flux in the main pole;
an auxiliary pole; and
an auxiliary electrically conductive coil coupled to the auxiliary pole for generating magnetic flux in the auxiliary pole at an angle to the main pole greater than 15 degrees and less than or equal to 90 degrees;
a write driver capable of supplying write current in two directions to the main coil; and
circuitry coupled to the auxiliary coil for energizing the auxiliary coil when the write driver switches the direction of write current to the main coil.
2. The system of claim 1 wherein the auxiliary pole is oriented substantially orthogonal to the main pole.
3. The system of claim 1 wherein the main coil is a multiple-turn coil wherein all of the coil turns lie in substantially the same plane.
4. The system of claim 3 wherein the auxiliary coil is a helical coil wrapped around the auxiliary pole.
5. The system of claim 1 wherein the main pole has a ferromagnetic resonance frequency and the circuitry coupled to the auxiliary coil energizes the auxiliary coil to generate an auxiliary magnetic field at said ferromagnetic resonance frequency.
6. The system of claim 1 wherein the write driver generates a primary signal at the write frequency, and wherein the circuitry coupled to the auxiliary coil comprises an oscillator for applying an auxiliary signal at a frequency greater than the write frequency.
7. The system of claim 6 wherein the write driver is coupled to the oscillator, and wherein the phase of the auxiliary signal from the oscillator is matched to the phase of the primary signal from the write driver.
8. The system of claim 1 wherein the write driver generates a primary signal, and wherein the circuitry coupled to the auxiliary coil comprises a high-pass filter for filtering from said primary signal a high-frequency component corresponding to the current-direction switching of the write current.
9. The system of claim 8 wherein the high-pass filter comprises two matched capacitors in series with the auxiliary coil, the auxiliary coil being located between the two capacitors.
10. The system of claim 1 wherein the write current from the write driver has a magnitude I w and wherein the circuitry coupled to the auxiliary coil generates auxiliary current (I a ) having a magnitude greater than about 0.2 I w .
11. A perpendicular magnetic recording write system for magnetizing regions in a perpendicular magnetic recording layer comprising:
a write head comprising
a main pole;
a main electrically conductive coil coupled to the main pole for generating magnetic flux in the main pole;
an auxiliary pole oriented substantially orthogonal to the main pole; and
an auxiliary electrically conductive coil coupled to the auxiliary pole for generating magnetic flux in the auxiliary pole;
a write driver for generating a primary signal to supply write current in two directions to the main coil; and
circuitry coupled to the auxiliary coil for energizing the auxiliary coil when the write driver switches the direction of write current to the main coil, the circuitry comprising a high-pass filter for filtering from said primary signal a high-frequency component corresponding to the current-direction switching of the write current.
12. The system of claim 11 wherein the main coil is a multiple-turn coil wherein all of the coil turns lie in substantially the same plane.
13. The system of claim 12 wherein the auxiliary coil is a helical coil wrapped around the auxiliary pole.
14. The system of claim 11 wherein the high-pass filter comprises two matched capacitors in series with the auxiliary coil, the auxiliary coil being located between the two capacitors.
15. The system of claim 11 wherein the write current from the write driver has a magnitude I w and wherein the circuitry coupled to the auxiliary coil generates auxiliary current (I a ) having a magnitude greater than about 0.2 I w .
16. The system of claim 11 wherein the main pole has a ferromagnetic resonance frequency and wherein the frequency of said high-frequency component is said ferromagnetic resonance frequency.