Universal spin-flip transition in itinerant antiferromagnets

We reveal a universal spin-flip (SF) transition as a function of temperature in spin-density-wave (SDW) systems. At low temperatures the antiferromagnetic (AFM) polarization is parallel to the applied field and above a critical temperature the AFM polarization flips perpendicular to the field. This transition occurs in any SDW system and may be considered as a qualitative probe of the itinerant character of AFM in a given material. Our SF transition may provide an explanation to the long-standing puzzle of the SF transition observed in chromium and may be at the origin of the equally puzzling SDW-I to SDW-II transition in Bechgaard salts for which we make experimental predictions.