Antiferromagnetic-ferromagnetic phase transition in FeRh probed by x-ray magnetic circular dichroism

The phase transition from antiferromagnetic to ferromagnetic ordering in FeRh is investigated in an element specific way by means of x-ray absorption spectroscopy. Dichroism sum rules allow us to determine spin and orbital moments of the two elements as the system is driven through the phase transition. Increasing the temperature from 300 to 450 K, the magnetic moments in Fe and Rh both evolve from zero to their final value, while the ratio of Rh to Fe moments stays constant. Our experimental findings are supported by the results of fully relativistic ab initio calculations.