High-Field Magnetoresistance of bcc Iron

The transverse magnetoresistance of single crystals of bcc iron of the highest available purity, measured at a temperature of 4.2°K in applied magnetic fields up to 100 kOe, has a magnitude and field dependence which show that this metal is compensated. The curves showing the magnetoresistance as a function of the direction of the magnetic field exhibit narrow minima when the field lies in a {110} plane near a $〈001〉$ axis and in a {001} plane near a $〈110〉$ axis. These minima are attributed to sets of periodic open orbits directed along the $〈110〉$ and $〈001〉$ axes, respectively. The absence of complete saturation of the magnetoresistance, when the magnetic field is at any one of the minima, suggests either that the number of open orbits is very small, or that they result from magnetic breakdown. To distinguish experimentally between these two possibilities will require the use of higher magnetic fields and/or purer samples.