Magnetic recording assisted by spin torque oscillator with a radio frequency current bias

A microwave assisted magnetic recording (MAMR) structure that includes a write head, comprising:

• (a) a main pole that generates a magnetic flux field which is directed through a pole tip at an air bearing surface (ABS) and into a magnetic medium comprised of a plurality of bits, the magnetic flux has a gap field component that is directed across a spin torque oscillator (STO) and into a write shield;
• (b) the write shield with a side along the ABS that collects magnetic flux which has passed through the magnetic medium and written one or more bits;
• (c) the STO that is formed along the ABS and has a NM1/SP/NM3/OL/NM2 configuration wherein a first non-magnetic layer (NM1) adjoins the main pole, a second non-magnetic layer (NM2) contacts the write shield, SP is a layer with perpendicular magnetic anisotropy that spin polarizes direct current (dc) and radio frequency (rf) current passing there through, NM3 is a third non-magnetic layer between SP and OL layers, and OL is a layer with a magnetization that reaches a large angle oscillation state with an oscillation frequency when a threshold current with density (jc) that is spin polarized by the SP layer exerts a spin transfer torque on the OL layer such that the large angle OL oscillation generates a rf field on the magnetic medium and assists the writing to one or more bits;
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• (d) a bias tee (T) that is electrically connected by a lead to the main pole and by a lead to the write shield, and combines dc from a dc source and rf current from a rf current source and injects the dc and rf current combination into the STO through a main pole terminal or a write shield terminal to provide a dc bias, and a rf bias to the STO.