Effect of substrate rotation on domain structure and magnetic relaxation in magnetic antidot lattice arrays

Abstract

Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.

Relaxation dynamics in magnetic antidot lattice arrays of Co/Pt with perpendicular anisotropy

“…To overcome the additional pinning, the reversal field increases for the MAL arrays. This in principle is a general behavior for MAL arrays irrespective of their anisotropy and architecture 9 , 10 , 12 , 13 . However the shape of the loops (shown in Fig.…”

“…It is observed that although in case of the Co/Pt MAL arrays with PMA the reversal is nucleation dominated, however, the overall nature of the bubble domains is similar to its parent continuous thin film. It should be noted that, this behavior is different when comparing the domains of MAL arrays having in-plane anisotropy to their parent thin films 9 , 10 .

Figure 3 ( a – c ) and ( d – f ) are the domain images at - H S , H N , and H C , for samples ES1 and ES2, respectively.

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“…dimension not being restricted by the superparamagnetic limit 4 to the bit size, feasibility of tuning the spin waves as magneto-photonic crystals 5 , etc. Most of the works on the MALs so far have been focused on the in-plane magnetized systems where the lateral movement of the domain walls are engineered by incorporating the periodic holes 6 – 9 . The presence of these periodic holes in such in-plane magnetized MAL arrays hinders the path of propagation of the domains in lateral direction which essentially slows down the magnetic relaxation mechanism 9 , 10 .…”

“…Most of the works on the MALs so far have been focused on the in-plane magnetized systems where the lateral movement of the domain walls are engineered by incorporating the periodic holes 6 – 9 . The presence of these periodic holes in such in-plane magnetized MAL arrays hinders the path of propagation of the domains in lateral direction which essentially slows down the magnetic relaxation mechanism 9 , 10 . Our previous work about relaxation behavior in Co in-plane magnetized systems reveal that the relaxation time increases from 4.09 s in continuous thin film to 34.05 s of micro-dimensional triangular antidots 10 , 11 .…”

Strain engineered domain structure and their relaxation in perpendicularly magnetized Co/Pt deposited on flexible polyimide

“…Here the normalized intensity as a function of time basically reflects the net magnetization relaxation of the sample. Amongst various raised models to explain magnetization relaxation phenomena Fatuzzo-Labrune model is extensively used for FM thin films [38][39][40][41][42][43]. However, the approximation of single energy barrier made in this model does not hold for a real thin film which consists of a distribution of energy barrier with defects and inhomogeneity throughout the surface.…”