Tunnel junction sensor with a multilayer free-layer structure

A method for fabricating a thin film tunnel junction sensor for sensing an external magnetic field comprising the steps of:

• depositing an antiferromagnetic layer;
• depositing a pinned ferromagnetic layer;
• depositing a barrier layer in contact with the pinned ferromagnetic layer;
• and
• depositing a free layer structure including:
• a first layer of ferromagnetic material disposed adjacent to the barrier layer and having a first magnetostriction value which is positive and a first coercivity;
• a second layer of ferromagnetic material having a second magnetostriction value which is negative and a second coercivity;
• and
• a third layer of ferromagnetic material having a third magnetostriction value and a third coercivity, the third coercivity being lower than the second coercivity and the first, second and third magnetostriction values summing to approximately zero.

A disk drive comprising:

• a thin film disk including a thin film of ferromagnetic material on a planar surface of the disk;
• a spindle rotatably supporting the disk;
• and
• a tunnel junction magnetic sensor having an air bearing surface supported over the planar surface of the disk, the magnetic sensor including:
• a antiferromagnetic layer;
• a pinned layer;
• a barrier layer adjacent to the pinned layer;
• a magnetoresistive layer disposed adjacent to the barrier layer and having a first magnetostriction which is positive;
• a negative magnetostriction layer disposed adjacent to the magnetoresistive layer and having a second magnetostriction which is negative;
• and
• a softening ferromagnetic layer disposed adjacent to the negative magnetostriction layer, having a coercivity lower than a coercivity of the negative magnetostriction layer and having a third magnetostriction which results in approximately zero total magnetostriction when summed with the first and second magnetostriction.