Suppression of thermally activated magnetization fluctuations in magnetoresistive elements via spin momentum transfer

A magnetoresistive (MR) element comprising:

• a reference layer having a magnetization pinned in a fixed direction;
• a free layer having a magnetization which rotates in response to an external magnetic field;
• a spacer layer positioned between the reference layer and the free layer;
• and
• a circuit for providing a current perpendicular to a plane of each of the layers in a direction that causes a reduction in thermally activated spin wave noise.

A magnetoresistive (MR) element having reduced thermally activated spin wave noise, the MR element comprising:

• a first reference layer having a magnetization pinned in a fixed direction;
• a first free layer having a magnetization which rotates in response to an external magnetic field;
• a second free layer having a magnetization which rotates in response to an external magnetic field;
• a second reference layer having a magnetization pinned in a fixed direction;
• a nonmagnetic layer positioned between the first free layer and the second free layer;
• a first spacer layer positioned between the first reference layer and the first free layer;
• a second spacer layer positioned between the second free layer and the second reference layer;
• and
• a circuit for providing a current perpendicular to a plane of each of the layers such that the current exerts a spin momentum transfer torque on localized electron spins in the free layers, thereby reducing noise in the free layers.

A method of sensing magnetically encoded information from a magnetic storage medium, the method comprising:

• causing relative motion of the storage medium with respect to a current perpendicular to plane (CPP) magnetoresistive (MR) element;
• directing a spin polarized current through the CPP MR element in a direction which exerts a spin momentum transfer that reduces noise due to thermally activated spin waves;
• and
• detecting a voltage across the CPP MR element.