Write current undershoot for a heat-assisted magnetic storage device
An apparatus includes a write head. A preamplifier is coupled to the write head. A controller is coupled to the preamplifier and configured to cause the preamplifier to apply an overshoot current to the write head for a predefined overshoot current duration, apply an undershoot current to the write head for a predefined undershoot current duration, and apply a steady-state current to the write head after the undershoot current duration, the steady-state current being greater than the undershoot current.
1 . A heat-assisted magnetic recording device, comprising:
a write head comprising a near-field transducer configured to transmit energy to create a thermal spot on a recording medium; and
a preamplifier coupled to the write head; and
a controller coupled to the preamplifier and configured to cause the preamplifier to:
apply an overshoot current to the write head for a predefined overshoot current duration during writing of a bit;
apply an undershoot current to the write head for a predefined undershoot current duration during writing the bit; and
apply, after the undershoot current duration, a steady-state current to the write head during writing the bit and while the near-field transducer is transmitting energy to the recording medium, the steady-state current being greater than the undershoot current.
2 . The device of claim 1 , wherein at least one of the undershoot current and the undershoot current duration are adjustable.
3 . The device of claim 1 , wherein the undershoot current is in a range of 20% to 50% of the steady-state current.
4 . The device of claim 1 , wherein the undershoot current is in a range of 30% to 45% of the steady-state current.
5 . The device of claim 1 , wherein the undershoot current is negative.
6 . The device of claim 1 , wherein the undershoot duration is in a range of 30 ps to 700 ps.
7 . The device of claim 1 , wherein the undershoot duration is in a range of 50 ps to 500 ps.
8 . The device of claim 1 , wherein the overshoot duration is in a range of about 90 ps to about 500 ps.
9 . A method for modulating current in a heat assisted magnetic recording device comprising:
applying an overshoot current to a write head for a predefined overshoot current duration during writing of a bit;
applying an undershoot current to the write head for a predefined undershoot current duration during writing of the bit; and
applying, after the undershoot current duration, a steady-state current to the write head during writing of the bit and while a near-field transducer is transmitting energy to a recording medium, the steady-state current being greater than the undershoot current.
10 . The method of claim 9 , wherein at least one of the undershoot current and the undershoot current duration are adjustable.
11 . The method of claim 9 , wherein the undershoot current is in a range of 20% to 40% of the steady-state current.
12 . The method of claim 9 , wherein the undershoot current is negative.
13 . The method of claim 9 , wherein the undershoot duration is in a range of 30 ps to 700 ps.
14 . The method of claim 9 , wherein the undershoot duration is in a range of 50 ps to 500 ps.
15 . The method of claim 9 , wherein the overshoot duration is in a range of about 90 ps to about 500 ps.
16 . An apparatus, comprising:
an interface circuit operable to communicate with a write head, the write head comprising a near-field transducer configured to transmit energy to create a thermal spot on a recording medium;
a controller coupled to the interface circuit, the controller operable to provide instructions to the interface circuit to:
apply an overshoot current to the write head for a predefined overshoot current duration during writing of a bit;
apply an undershoot current to the write head for a predefined undershoot current duration during writing of the bit; and
apply, after the undershoot current duration, a steady-state current to the write head during writing the bit and while the near-field transducer is transmitting energy to the recording medium, the steady-state current being greater than the undershoot current.
17 . The apparatus of claim 16 , wherein the interface circuit comprises a preamplifier.
18 . The apparatus of claim 16 , wherein at least one of the undershoot current and the undershoot current duration are adjustable.
19 . The apparatus of claim 16 , wherein the undershoot current is in a range of 20% to 50% of the steady-state current.
20 . The apparatus of claim 16 , wherein the undershoot current is in a range of 30% to 45% of the steady-state current.