Microscopic reversal magnetization mechanisms in CoCrPt thin films with perpendicular magnetic anisotropy: Fractal structure versus labyrinth stripe domains

Abstract

The magnetization reversal of CoCrPt thin films has been examined as a function of thickness using magnetooptical Kerr effect (MOKE) microscopy and first-order reversal curves (FORC) techniques. MOKE images show differentiated magnetization reversal regimes for different film thicknesses: while the magnetic domains in 10-nm-thick CoCrPt film resemble a fractal structure, a labyrinth stripe domain configuration is observed for 20-nm-thick films. Although FORC distributions for both cases show two main features related to irreversible processes (propagation and annihilation fields) separated by a mostly flat region, this method can nonetheless distinguish which magnetization reversal process is active according to the horizontal profile of the first FORC peak, or propagation field. A single-peak FORC profile corresponds to the fractal magnetization reversal, whereas a flat-peak FORC profile corresponds to the labyrinth magnetization reversal.

Magneto-optical study of anomalous magnetization reversal in the presence of anisotropy dispersion in CoPd thin films

“…An accurate recognition of magnetic properties in this two dimensional geometry is required for different applications. In this regard, magnetization reversal data give a lot of information about magnetic anisotropy [1,2], exchange bias coupling [3,4], exchange spring effect [5][6][7], etc. Magnetization reversal is particularly complex in magnetic systems with large anisotropy dispersion, as highlighted by numerous studies [8][9][10][11][12][13].…”

FORC signatures and switching-field distributions of dipolar coupled nanowire-based hysterons

“…Next step is to overcome some of the assumptions, for example in introducing a magnetizing coupling between magnets, such as exchange interaction or magnetizing dipolar interactions in assemblies where aligned easy axes lie in the assembly plane. In addition to the extraction of extrinsic and intrinsic parameters, FORC is also an exciting tool to probe fingerprints related to the reversal processes such as distributions related to nucleation/annihilation of magnetic domain in thin films [18] [19] or vortex in [25]. Such behaviours cannot be addressed using the hysteron-based approach and thus require FORC modelling with the use of micromagnetic simulations, which are up to now time-consuming and limits a broad scanning of parameters.…”

“…1) FORC analysis is now widely used in several laboratories because of its implementation simplicity [3,5]. Focusing on magnetic systems, FORC technique has been used to investigate diverse systems such as rock and mineral magnetism [3,6,7,8], magnetic media [9,10,11,12], GMR spin valves [13], magnetic tunnel junctions [14], thin films [15,16,17,18], magnetic multilayers with perpendicular magnetic anisotropy [19,20,21,22,23,24], magnetic dot/pillar assemblies [25,26,27], permanent magnets [28,29], exchange spring magnets [30], and nanowire assemblies [31,32,33,34,35,36,37,38,39,40,41,42], since isolated small diameter nanowires behave as basic hysterons. However, the understanding of the resulting FORC diagrams is not straightforward as it does not strictly represent the Preisach distribution.…”

MFM and first order reversal curve (FORC) study of switching mechanism in Co25Pd75 films

“…The mechanism by which a thin magnetic film switches when the magnetic field is changed has been studied by various imaging techniques such as MOKE (magneto-optical Kerr effect) 3,4 and Lorentz microscopy 5,6 . These techniques are difficult and time-consumingit is attractive to use the more accessible technique of magnetic force microscopy (MFM) 7,8 , but MFM cannot easily be used in a nonzero magnetic field, and only one of the states along a hysteresis curve (the remanent state, the red dot in Fig.…”