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Magnetic Reversal and Microstructure Phases in Antiferromagnetically Coupled Multilayer Systems with Perpendicular Anisotropy
Hellwig, O.;
Strong perpendicular anisotropy systems consisting of Co/Pt or Co/Pd multilayer stacks that are antiferromagnetically coupled via thin Ru or Ir layers have been used as model systems to study the competition between interlayer exchange, perpendicular anisotropy and long-range dipolar interactions [1,2]. The typical layer structure for such systems is illustrated in Fig.1 for a [(Co/Pt)Co/Ru] multilayer system.
Magnetometry and Magnetic Force Microscopy (MFM) studies of such systems reveal complex magnetic phases with a mix of tilted versus non-tilted and antiferromagnetic (AF) versus ferromagnetic (FM) phases depending on the dominance of the various energy contributions. For thin Co/Pt multilayer blocks AF-exchange is dominating and the magnetic structure remains laterally uniform at any stage of the reversal process and is for even number of AF-coupled blocks characterized by bulk and surface spin-flop transitions as shown on the left in Fig. 2. For thicker Co/Pt multilayer blocks the perpendicular anisotropy term takes the lead and prevents any tilting of the spins away from the easy axis normal to the film plane. In this case the reversal into the AF-coupled remanent state occurs via FM/AFM domain formation as shown in the middle part of Fig. 2. For even thicker Co/Pt multilayer blocks the AF-exchange is also overcome by the demagnetization energy and the uniform AF remanent state is replaced by a laterally heterogeneous FM stripe domain state, as illustrated in Fig. 2 on the right.
Ion beam irradiation may be able to control the rich variety of phases in this system on a nanoscopic length scale, thus allowing for a lateral co-existance of all these phases within one and the same sample. This could allow fabricating an infrastructure for controlled spin-wave propagation, such as motivated by recent studies for domain walls and perpendicular anisotropy systems [3,4]. Examples of such initial studies will be discussed.
  • Lecture (Conference)
    Intermag 2017, 24.-28.04.2017, Dublin, Ireland

Publ.-Id: 24882 - Permalink