Systematic variation of the strength and oscillation period of indirect magnetic exchange coupling through the 3d, 4d, and 5dtransition metals

We show that oscillatory indirect magnetic exchange coupling via transition metals sandwiched between ferromagnetic layers of Fe, Co, Ni, or Ni alloys is a general phenomeonon. Surprisingly, the oscillation period is approximately the same, 10, in all the transition metals in which we observe coupling with the single exception of Cr, for which it is much longer. Furthermore, the exchange-coupling strength is found to increase systematically from the 5d to 4d to 3d metals and exponentially with increasing number of d electrons along each period.