Spin transfer torque oscillator (STO) with spin torque injection to a flux generating layer (FGL) from two sides

A perpendicular magnetic recording (PMR) writer with a spin torque reversal assisted magnetic recording (STRAMR) structure, comprising:

• (a) a main pole (MP) that is configured to generate a magnetic (write) field which is directed through a pole tip at an air bearing surface (ABS), and a write gap (WG) field flux in a down-track direction from a MP trailing side across the WG and a spin torque oscillator (STO) device into a trailing shield (TS);
• (b) the trailing shield (TS) with a side at the ABS, and a bottom surface facing the MP;
• and
• (c) the STO device, comprising:
• (1) a first spin polarization layer (SP1) that adjoins the MP trailing side, and a second spin polarization layer (SP2) that contacts the TS bottom surface;
• (2) first and second spin preserving layers (SPRL1 and SPRL2), wherein SPRL1 adjoins the SP1 on a side opposite to the MP trailing side, and SPRL2 contacts the SP2 on a side opposite to the TS bottom surface;
• and
• (3) a field generation layer (FGL) formed between SPRL1 and SPRL2, and having a front side at the ABS and a backside at a height (h2), and with a magnetization pointing substantially in the direction of the WG field flux in the absence of an applied current, and wherein the STO device is configured so that when a current (1a) of sufficient magnitude from a direct current (dc) source is applied from the MP trailing side across the SP1 and SPRL1 to the FGL and returns through a lead to the dc source, and a current (1b) from the dc source is applied from the TS bottom surface across the SP2 and SPRL2 to the FGL and returns through the lead to the dc source, the SP1 and SP2 exert an additive spin torque on the FGL to cause a FGL precessional state that produces one or both of a radio frequency field on a magnetic medium to reduce a write field needed to switch a bit magnetization therein, and flips the FGL magnetization to a direction substantially antiparallel to the WG field flux thereby increasing reluctance in the WG, which enhances the write field.