GMR spin valve structure using heusler alloy

#The present invention relates to magnetic sensors. More particularly, the present invention relates to giant magnetoresistive (GMR) spin valve magnetoresistive sensors.

#Magnetic sensors utilizing the GMR effect, frequently referred to as “spin valve” sensors, are known in the art. A spin valve sensor is typically a sandwiched structure consisting of two ferromagnetic layers separated by a thin non-ferromagnetic layer. One of the ferromagnetic layers is called the “pinned layer” because it is magnetically pinned or oriented in a fixed and unchanging direction by an adjacent anti-ferromagnetic layer, commonly referred to as the “pinning layer,” through anti-ferromagnetic exchange coupling. The other ferromagnetic layer is called the “free” or “unpinned” layer because the magnetization is allowed to rotate in response to the presence of external magnetic fields.

#In a giant magnetoresistive sensor, a sense current is applied to the sensor and travels in the plane of the layers. In the presence of a magnetic field such as that provided by magnetic storage medium, the resistance of the sensor changes resulting in a change in voltage across the sensor due to the applied sense current. This voltage change may be measured and used to read back information. The operation of one configuration of a GMR sensor is described in U.S. Pat. No. 4,949,036, issued Aug. 14, 1990 to Grunberg, entitled “MAGNETIC FIELD SENSOR WITH FERROMAGNETIC THIN LAYERS HAVING MAGNETICALLY

#FIG. 1A is a perspective view of a disc storage system.

#FIG. 1B is a simplified diagram of a storage system in accordance with the present invention.

#FIG. 2A shows the crystal structure of a full Heusler alloy A2MnB.

#The present invention relates to magnetoresistive sensors of the giant magnetoresistive (GMR or spin valve) type which are used to read back information from storage media such as magnetic discs. One aspect of the present invention includes a GMR sensor having ferromagnetic layers of Heusler alloy can be achieved by at least partially matching the energy bands of a non-ferromagnetic spacer to the energy bands for one of the spin states (majority or minority) of the ferromagnetic layers.

#FIG. 1A is an isometric view of a disc drive 100 in which embodiments of the present invention are useful. Disc drive 100 includes a housing with a base 102 and a top cover (not shown). Disc drive 100 further includes a disc 106, which is mounted on a spindle motor (not shown) by a disc clamp 108. Disc 106 is part of a disc pack which includes a plurality of individual discs (storage media), which are mounted for co-rotation about central axis 109. Disc 106 has an associated disc head slider 110 which is mounted to disc drive 100 for communication with the disc surface. In the example shown in FIG. 1A, slider 110 is supported by suspension 112 which is in turn attached to a track accessing arm 114 of an actuator 116. The actuator shown in FIG. 1A is of the type known as a rotary moving coil actuator and includes a voice coil motor (VCM), shown generally at 118. Voice coil motor 118 rotates actuator 116 with its attached heads 110 about a pivot shaft 120 to position heads 110 over a desired data track along an arcuate path 122 between a disc inner diameter 124 and a disc outer diameter 126. Voice coil motor 118 is driven by servo electronics 130 based on signals generated by heads 110 and a host computer (not shown). Head assembly 110 includes a “slider” which carries a magnetic head (not shown in FIG. 1A) for perpendicular recording onto a surface of a disc.

#The present invention includes a new spin valve sensor which may be used in a data storage system such as data storage system 100 shown FIG. 1A. FIG. 1B is a simplified block diagram showing system 100, storage medium 108 which is rotated by motor 140. A controller 138 controls positioning of the slider 110. A magnetoresistive sensor on slider 110 operates by receiving a sense (or bias) current I from current source 142. Variations in a magnetic field applied to the magnetoresistive sensor due to magnetization of disc 106 cause a change in the electrical resistance of the sensor. This change in electrical resistance is detected with read-back circuitry 144 which responsively provides data output.