Magnetic sensor exhibiting large change in resistance at low external magnetic field

A magnetoresistive sensor comprising:

• a plurality of multilayered magnetoresistive films formed on a substrate, each multilayered magnetoresistive film containing a pinned ferromagnetic layer and a free magnetic layer, reversion of magnetization of said pinned ferromagnetic layer being pinned, and a vector of magnetization of said free ferromagnetic layer freely reversing in response to an external magnetic field;
• and
• a hard magnetic layer provided under one of two adjacent multilayered magnetoresistive films;
• wherein after all the multilayered magnetoresistive films are magnetized by applying a magnetic field which is larger than the coercive force of the hard magnetic layer to the entire substrate, the entire substrate is magnetized by a magnetic field, which is larger than a coercive force of the pinned ferromagnetic layer in the multilayered magnetoresistive film not having the hard magnetic layer, such that a vector of magnetization of the pinned ferromagnetic layer of the multilayered magnetoresistive film having the hard magnetic layer and a vector of magnetization of the pinned ferromagnetic layer of the multilayered magnetoresistive film not having the hard magnetic layer are substantially antiparallel to each other along an axis of current flow of a conductor;
• and
• the conductor connects the multilayered magnetoresistive film having the hard bias layer and the multilayered magnetoresistive film not having the hard bias layer in series and is provided with terminals disposed at ends thereof.

A magnetoresistive sensor comprising:

• a plurality of multilayered magnetoresistive films formed on a substrate, each multilayered magnetoresistive film containing a pinned ferromagnetic layer and a free magnetic layer, reversion of magnetization of said pinned ferromagnetic layer being pinned, and a vector of magnetization of said free ferromagnetic layer freely reversing in response to an external magnetic field;
• wherein the pinned ferromagnetic layer of each multilayered magnetoresistive film is individually magnetized with a magnetic head, such that a vector of magnetization of the pinned ferromagnetic layer in one multilayered magnetoresistive film among two adjacent multilayered magnetoresistive films is substantially antiparallel along an axis of current flow of a conductor to a vector of magnetization of the pinned ferromagnetic layer in the adjacent multilayered magnetoresistive film;
• and
• the conductor connects the adjacent multilayered magnetoresistive films in series and is provided with terminals disposed at ends thereof.

A magnetoresistive sensor comprising:

• a plurality of multilayered magnetoresistive films arranged in parallel to each other on a substrate, each multilayered magnetoresistive film containing a pinned ferromagnetic layer and a free magnetic layer, reversion of magnetization of said pinned ferromagnetic layer being pinned, and a vector of magnetization of said free ferromagnetic layer freely reversing in response to an external magnetic field;
• a hard magnetic layer provided under only one of two adjacent multilayered magnetoresistive films;
• and
• a conductor connecting the adjacent multilayered magnetoresistive films in series and provided with terminals disposed at ends thereof;
• wherein
• the vectors of magnetization of the pinned ferromagnetic layers in the adjacent multilayered magnetoresistive films are substantially antiparallel to each other;
• and
• a coercive force of the pinned ferromagnetic layer of the multilayered magnetoresistive film provided with said hard magnetic layer is higher than a coercive force of the pinned ferromagnetic layer of the adjacent multilayered magnetoresistive film.