Magnetization reversal processes in epitaxial NiO/NiFe bilayers were studied using the magneto-optic indicator film technique. The influence of dislocations on these processes was determined. Remagnetization parallel to the unidirectional anisotropy axis proceeds by domain nucleation and growth, with nucleation center activity being asymmetric with respect to the applied field sign. Magnetization reversal in the hard axis direction occurs by incoherent rotation. The enhanced coercivity and asymmetric nucleation can be explained by taking into account domain wall behavior in the antiferromagnetic layer.
A new method is developed using a transparent indicator ferrimagnetic magneto-optic film with in-plane anisotropy for visualization and direct experimental study of dynamic magnetization processes and nondestructive characterization of the defect structure of magnetic multilayers. Some examples of its application to the investigation of peculiarities of the as-grown magnetic structure of electrochemically produced CoNiCu/Cu multilayers with a giant magnetoresistance (GMR) effect and magnetization reversal by domain wall motion are described.
To study the local magnetic anisotropy in the microstress field of dislocations a first experimental investigation of the magnetic moment distribution around single dislocations is carried out in gadolinium‐iron garnet single crystals at temperatures near the compensation point. It is established that under the conditions of weak dipolar interactions at dislocations characteristic rosettes of domains magnetized along different directions exist. Some peculiarities of their changes under the action of an external magnetic field and of temperature are studied. On the basis of magnetoelastic energy analysis it is shown that the magnetization and the form of dislocation domains are defined by the local anisotropy, induced in the dislocation elastic field, and their dimensions — by growth conditions of their nuclei arised in the vicinity of the defect core.
The possibility of the application of the photoelasticity method for revealing individual dislocations in single crystals of thirty elements and compounds transparent for visible and infrared light is estimated. Experimental proofs of the realization of this possibility are given in application to GaAs crystals in which edge dislocations are detected lying along 〈110〉 and 〈100〉 directions with Burgers vector along 〈110〉. Peculiarities of stress measurement in microregions around dislocations are described. The prospects of the photoelasticity method for the investigation of local changes of magnetic, electric, and optical crystal properties caused by the stress fields around individual dislocations are discussed as well.
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