How a Magnetoresistive Sensor Works

[AvroArrow]

Hi guys I am a new member here so I am looking for feedback on the quality and clarity of this post as well as a solution to the problem. If there are any suggestions as to how I can improve the format or wording of the question I am always looking to get better.

On to the question,

I am wondering how a magnetoresistive material changes its resistance based on the angle and strength of an external magnetic field.

I have a great resource here that explains how they work.:

http://sensors-actuators-info.blogspot.ca/2009/08/magnetoresistive-sensor.html I just don't get why the resistance of the magnet is largest when the current flow and internal magnetization vector are parallel and conversely why the resistance is the smallest when the angle is 90° between the current flow and the internal magnetization vector.

If the current and internal magnetization vector are parallel, then there is no magnetic force, so shouldn't the resistance be the lowest when they are parallel? When the two are at 90° there is a result magnetic force pushing the electrons perpendicular to the flow of current which I think should increase the resistance of the material. Is it the resultant magnetic force that causes the change in resistance in these ferromagnetic materials or something else?

Also is this internal magnetic vector M the net magnetic field from the randomly oriented domains in the ferromagnetic material?

I am really just looking for a great, fundamental explanation of magnetoresistive sensors, I need some assistance in how the magnet is changing its resistance from the changing external magnetic field.

Thanks in advance guys.

 

[Tom.G]

http://www.google.com/patents/US5408377

This one is more scholarly (harder):
ftp://132.163.4.45/pub/pappas/CNRS-APS%20Sensors/References/MR/TMR/Frietas_Magnetoresistive_sensors.pdf

The search was:
https://www.google.com/?gws_rd=ssl#q=magnetoresistive+sensor+theory