Tunneling magnetic sensing element having free layer containing CoFe alloy
A tunneling magnetic sensing element including an Mg—O insulating barrier which can maintain favorable soft-magnetic properties of a free magnetic layer and can have a high resistance change ratio (ΔR/R) compared to known tunnel magnetic sensing elements is disclosed, and a method of manufacturing such a tunneling magnetic sensing element is also disclosed. An enhance layer (second magnetic layer) composed of Co 100-X Fe X having a Fe composition ratio X of about 30 to 100 at % is disposed on the Mg—O insulating barrier. With this, the magnetostriction λ of the free magnetic layer can be reduced and the resistance change ratio (ΔR/R) can be increased.
1. A tunneling magnetic sensing element comprising:
a first magnetic layer, an insulating barrier disposed over the first magnetic layer, and a second magnetic layer disposed over the insulating barrier;
wherein the first magnetic layer constitutes at least a part of a pinned magnetic layer having a pinned magnetization direction;
wherein the second magnetic layer constitutes at least a part of a free magnetic layer having a magnetization direction being changed by an external magnetic field;
wherein the insulating barrier is composed of Mg—O;
wherein the second magnetic layer is composed of Co 100-x Fe x having a Fe composition ratio X of about 50 at % to 90 at %,
wherein the insulating barrier has a body-centered cubic structure in which an equivalent crystal plane typically represented as a {100} plane is preferentially oriented in the direction parallel to the interface,
wherein the second magnetic layer has a body-centered cubic structure in which an equivalent crystal plane typically represented as a {100} plane is preferentially oriented in the direction parallel to the interface,
wherein the first magnetic layer has an amorphous structure,
wherein the first magnetic layer is composed of (Co 100-Y Fe y ) z B 100-Z , the atomic ratio Y is about 25 to 100 at %, and the composition ratio Z is about 70 to 100 at %,
wherein the second magnetic layer is an enhance layer, and the free magnetic layer contains the enhance layer and a soft-magnetic layer which is composed of a NiFe-alloy and is disposed on the enhance layer, the Ni composition ratio in the NiFe-alloy is 81.5% to 100%, and
wherein the second magnetic layer is directly in contact with the insulating barrier, the soft-magnetic layer is directly in contact with the second magnetic layer.
2. The tunneling magnetic sensing element according to claim 1 , wherein the insulating barrier has a thickness between 8 to 20 angstroms.
3. The tunneling magnetic sensing element according to claim 1 , wherein the second magnetic layer has a thickness between 5 to 15 angstroms.
4. The tunneling magnetic sensing element according to claim 1 , wherein the soft magnetic layer has a thickness between 30 to 80 angstroms.