AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI+TF-WeA

Paper MI+TF-WeA9
The Effect of Interlayer Coupling to the Magnetic Phase Transition of Thin Films

Wednesday, November 5, 2003, 4:40 pm, Room 316

Session: Magnetic Thin Films
Presenter: C. Won, University of California at Berkeley
Authors: C. Won, University of California at Berkeley
Y.Z. Wu, University of California at Berkeley
A. Scholl, Lawrence Berkeley National Laboratory
A. Doran, Lawrence Berkeley National Laboratory
N. Kurahashi, University of California at Berkeley
H.W. Zhao, University of California at Berkeley
Z.Q. Qiu, University of California at Berkeley
Correspondent: Click to Email
Magnetic phase transition of two-dimensional systems is one of the intensively studied topic in condensed matter physics. One of the basic questions on this subject is how the addition of the interlayer coupling changes the magnetic phase transition. The coupled magnetic sandwiches of Co/Fe/Ni/Cu(100) and Co/Cu/Ni/Cu(100) were investigated by photoemission electron microscopy(PEEM). Element-specific magnetic domain images were taken at room temperature to reveal the critical thickness at which the magnetic phase transition occurs. The phase diagrams with thickness of each magnetic film were constructed under a few selected coupling conditions. The results shows three different types of magnetic phase transitions depending on the relative ferromagnetic film thickness. If the magnetic orders of two magnetic films are similar, both films undergo magnetic phase transition simultaneously. This means the lost of magnetic order of one film can be compensated by the interlayer coupling with the other magnetic film and two magnetic films are highly correlated each other in the interlayer coupling strength. Other two phase-transitions happened when one film is coupled with the other film that is too thin to have magnetism even with the help of coupling or that is ferromagnetic already by its own magnetic order. The difference of the critical thickness for these two cases shows that interlayer coupling increases Curie temperature. The strength and sign of coupling was changed to see how the coupling strength changes this behavior and we found that not the sign but the coupling strength has main role in the phase transition. And Monte-Carlo simulations based on 2 dimensional Ising model were performed to explain this experimental results.