Temperature and angular dependence of the anisotropic magnetoresistance in epitaxial Fe films

We perform detailed temperature dependent measurements of the magnetoresistance (MR) and its angular dependence of epitaxial Fe (110) films. The angular dependence of the MR at $H=10$ kOe is found to change strongly when going from $T=4.2$ K to $T=230$ K. We analyze the data on the basis of D\"oring's equation. Second- and fourth-order angular dependent terms are found to be of equal importance, indicating strong deviations of the MR from a simple cos²φ dependence. One of the MR components is the ordinary or Lorentz magnetoresistance, which is strong at low temperatures and becomes smaller at higher temperatures, due to the reduction of the mean free path. By subtracting the ordinary magnetoresistance from the MR data we obtain the anisotropic magnetoresistance. We decompose the temperature dependent anisotropic magnetoresistance in the temperature dependent k constants of D\"oring's equation. These constants show a reduction between $T=20$ K and $T=100$ K, which reflects the observed decrease of the anisotropic magnetoresistance. We present arguments that the temperature dependence of the anisotropic magnetoresistance is most likely due to the change from defect-dominated scattering to phonon-dominated scattering, each of which has its own anisotropic magnetoresistance.