Magnetic field sensor for sensing external magnetic field

摘要

A magnetic field sensor for sensing an external magnetic field is disclosed. The magnetic field sensor includes at least two magnetic tunneling junction (MTJ) elements disposed on an underlying electrode. Each of the MTJ elements is formed by a synthetic antiferromagnetic layer, a barrier layer and a free layer sequentially stacked together. A top electrode is then connected to the free layers. The free layer can be a single free layer, a composite free layer, a synthetic antiferromagnetic free layer or an alloy free layer. When a current is applied to a metal circuit passing over or below the MTJ elements, free magnetic moments generated by the MTJ elements are anti-parallel to each other along a reference axis, and the angles between the magnetic moments created by the MTJ elements and the reference axis are 40 to 50 degrees and 130 to 140 degrees, respectively.

主权项

1. A biaxial magnetic field sensor, comprising:
a first magnetic field sensor having a first fixed direction and a first reference axis; and a second magnetic field sensor having a second fixed direction and a second reference axis, the first and the second reference axes form a 90-degree angle, and the first and the second fixed directions are parallel to each other and form 45-degree angles with the first and the second reference axes, respectively, wherein the first magnetic field sensor includes:
a first electrode and a second electrode disposed on a first substrate;a first magnetic tunneling junction (MTJ) element and a second MTJ element disposed between and connected in parallel with the first and the second electrodes, the first and the second MTJ elements being disposed along the first reference axis of the first magnetic field sensor, wherein the first MTJ element includes a first antiferromagnetic layer having a first pinned magnetic moment in the first fixed direction, a first free layer having a first free magnetic moment and a barrier layer formed between the first antiferromagnetic layer and the first free layer, and the first free layer is a multilayer structure, and wherein the second MTJ element includes a second antiferromagnetic layer having a second pinned magnetic moment in the first fixed direction, a second free layer having a second magnetic moment and a barrier layer formed between the second antiferromagnetic layer and the second free layer, and the second free layer is a multilayer structure; and
a first metal circuit passing over or below the first and the second MTJ elements, such that the first free magnetic moment and the second free magnetic moment are anti-parallel to each other along the first reference axis, and the first pinned magnetic moment and the second pinned magnetic moment form angles of 45 or 135 degrees with the first reference axis, respectively, and a magnetic field sensing direction of the first magnetic field sensor is perpendicular to the first reference axis, wherein the second magnetic field sensor includes:
a third electrode and a fourth electrode disposed on a second substrate;a third MTJ element and a fourth MTJ element disposed between and connected in parallel with the third and the fourth electrodes, the third and the fourth MTJ elements being disposed along the second reference axis of the second magnetic field sensor, wherein the third MTJ element includes a third antiferromagnetic layer having a third pinned magnetic moment in the second fixed direction, a third free layer having a third free magnetic moment and a barrier layer formed between the third antiferromagnetic layer and the third free layer, and the third free layer is a multilayer structure, and wherein the fourth MTJ element includes a fourth antiferromagnetic layer having a fourth pinned magnetic moment in the second fixed direction, a fourth free layer having a fourth free magnetic moment and a barrier layer formed between the fourth antiferromagnetic layer and the fourth free layer, and the fourth free layer is a multilayer structure; and
a second metal circuit passing over or below the third and the fourth MTJ elements, such that the third free magnetic moment and the fourth free magnetic moment are anti-parallel to each other along the second reference axis, and the third pinned magnetic moment and the fourth pinned magnetic moment form angles of 45 or 135 degrees with the second reference axis, respectively, and a magnetic field sensing direction of the second magnetic field sensor is perpendicular to the second reference axis.