The definition of magnetoresistance effect refers to the phenomenon that the resistance value of some metals or semiconductors changes with the change of external magnetic field. When the carriers of metal or semiconductor move in the magnetic field, they are subjected to Lorentz force caused by the change of electromagnetic field, resulting in magnetoresistance effect. Extended data magnetoresistance effect refers to the phenomenon that the resistance value of some metals or semiconductors changes with the change of applied magnetic field. Like Hall effect, magnetoresistance effect is caused by Lorentz force on carriers in magnetic field. When the steady state is reached, the electric field force on carriers is equal to Lorentz force at a certain speed, and carriers gather at both ends to produce Hall electric field. Carriers slower than this speed will deflect in the direction of electric field force, while carriers faster than this speed will deflect in the direction of Lorentz force. This deflection leads to an increase in the carrier drift path. In other words, the number of carriers moving in the direction of the applied electric field decreases, thus increasing the resistance. This phenomenon is called magnetoresistive effect.