Mlu cell for sensing an external magnetic field and a magnetic sensor device comprising the mlu cell

A magnetic sensor device for sensing an external magnetic field, comprising:

• a plurality of branches, each branch comprising a subset of a plurality of MLU cells,
• each MLU cell comprising a magnetic tunnel junction including a sense layer having a sense magnetization adapted to be oriented by the external magnetic field;
• a reference layer having a reference magnetization;
• a reference antiferromagnetic layer pinning the reference magnetization at a low threshold temperature and freeing the reference magnetization at a high threshold temperature;
• and a tunnel barrier layer between the sense layer and the reference layer;
• a biasing layer having a biasing magnetization and a biasing antiferromagnetic layer pinning the biasing magnetization at the low threshold temperature and freeing the biasing magnetization at the high threshold temperature;
• the pinned biasing magnetization being oriented substantially parallel to the pinned reference magnetization;
• and a biasing coupling layer between the sense layer and the basing layer, the biasing coupling layer comprising a magnetic material of the antiferromagnetic type and being configured for magnetically coupling the biasing layer and the sense layer such that the sense magnetization is oriented substantially perpendicular to the pinned biasing magnetization and to the pinned reference magnetization;
• the magnetic tunnel junction further comprising a non-magnetic spacer layer between the sense layer and the biasing coupling layer, the non-magnetic spacer layer comprising one of:
• Ta, Mg, Al, Ru, Cu, Pt, Pd, Hf, Cr, Nb, Zn or any alloy or oxide containing any one of these elements, and being configured for tuning the strength of the magnetic coupling of the coupling layer;
• each subset being electrically connected in series by a current line configured for passing a programming current adapted for heating the MLU cells in the subset above the high threshold temperature such as to free the reference magnetization and the biasing magnetization;
• each branch further comprising means for applying a programming magnetic field configured for aligning the reference magnetization and the biasing magnetization of the MLU cells comprised in the subset in a programmed direction, when the MLU cells are heated at the high threshold temperature.

A method for programming a magnetic sensor device comprising a plurality of branches, each branch comprising a subset of a plurality of MLU cells;

• each MLU cell comprising a magnetic tunnel junction including a sense layer having a sense magnetization adapted to be oriented by the external magnetic field;
• a reference layer having a reference magnetization;
• a reference antiferromagnetic layer pinning the reference magnetization at a low threshold temperature and freeing the reference magnetization at a high threshold temperature;
• and a tunnel barrier layer between the sense layer and the reference layer;
• a biasing layer having a biasing magnetization and a biasing antiferromagnetic layer pinning the biasing magnetization at the low threshold temperature and freeing the biasing magnetization at the high threshold temperature;
• the pinned biasing magnetization being oriented substantially parallel to the pinned reference magnetization;
• and a biasing coupling layer between the sense layer and the basing layer, the biasing coupling layer comprising a magnetic material of the antiferromagnetic type and being configured for magnetically coupling the biasing layer and the sense layer such that the sense magnetization is oriented substantially perpendicular to the pinned biasing magnetization and to the pinned reference magnetization;
• the magnetic tunnel junction further comprising a non-magnetic spacer layer between the sense layer and the biasing coupling layer, the non-magnetic spacer layer comprising one of:
• Ta, Mg, Al, Ru, Cu, Pt, Pd, Hf, Cr, Nb, Zn or any alloy or oxide containing any one of these elements, and being configured for tuning the strength of the magnetic coupling of the coupling layer;
• each subset being electrically connected in series by a current line configured for passing a programming current adapted for heating the MLU cells in the subset above the high threshold temperature such as to free the reference magnetization and the biasing magnetization;
• each branch further comprising means for applying a programming magnetic field configured for aligning the reference magnetization and the biasing magnetization of the MLU cells comprised in the subset in a programmed direction, when the MLU cells are heated at the high threshold temperature;
• the method comprising:
• passing the heating current in the current line such as to heat the MLU cells comprised in the corresponding subset at the high threshold temperature and unpin the reference magnetization and the biasing magnetization;
• once the MLU cells comprised in the subset are heated at the high threshold temperature, applying a programming magnetic field for aligning the reference magnetization and the biasing magnetization of the MLU cells comprised in the subset in a programmed direction;
• cooling the MLU cells comprised in the subset to the low threshold temperature such as to pin the switching the reference magnetization and the biasing magnetization in the programmed direction, the sense magnetization being aligned substantially perpendicular to the programmed direction.

A method for sensing an external magnetic field by using the magnetic sensor device comprising a plurality of branches, each branch comprising a subset of a plurality of MLU cells;

• each MLU cell comprising a magnetic tunnel junction including a sense layer having a sense magnetization adapted to be oriented by the external magnetic field;
• a reference layer having a reference magnetization;
• a reference antiferromagnetic layer pinning the reference magnetization at a low threshold temperature and freeing the reference magnetization at a high threshold temperature;
• and a tunnel barrier layer between the sense layer and the reference layer;
• a biasing layer having a biasing magnetization and a biasing antiferromagnetic layer pinning the biasing magnetization at the low threshold temperature and freeing the biasing magnetization at the high threshold temperature;
• the pinned biasing magnetization being oriented substantially parallel to the pinned reference magnetization;
• and a biasing coupling layer between the sense layer and the basing layer, the biasing coupling layer comprising a magnetic material of the antiferromagnetic type and being configured for magnetically coupling the biasing layer and the sense layer such that the sense magnetization is oriented substantially perpendicular to the pinned biasing magnetization and to the pinned reference magnetization;
• the magnetic tunnel junction further comprising a non-magnetic spacer layer between the sense layer and the biasing coupling layer, the non-magnetic spacer layer comprising one of:
• Ta, Mg, Al, Ru, Cu, Pt, Pd, Hf, Cr, Nb, Zn or any alloy or oxide containing any one of these elements, and being configured for tuning the strength of the magnetic coupling of the coupling layer;
• each subset being electrically connected in series by a current line configured for passing a programming current adapted for heating the MLU cells in the subset above the high threshold temperature such as to free the reference magnetization and the biasing magnetization;
• each branch further comprising means for applying a programming magnetic field configured for aligning the reference magnetization and the biasing magnetization of the MLU cells comprised in the subset in a programmed direction, when the MLU cells are heated at the high threshold temperature;
• the method comprising passing a sensing current in the current branches.