Spin Configuration in Antiferromagnetic Domain Walls of the NiO-Type Crystals

A calculation is carried out to determine in what way the spin axes vary in the antiferromagnetic domain wall of the NiO-type crystal. The problem can be written in a form of variation calculus to minimize the sum of exchange energy, elastic energy, and magnetic anisotropy energy in the wall region. Dividing the magnetic lattice into four sublattices, the spatial change of spin direction in each sublattice is determined as a function of spatial coordinate for all possible types of the wall. The wall-width and the stored energy in the wall are estimated, using an elastic constant of MnO, to be about 80 Å and 4 erg/cm 2 for the {001} wall in NiO, and 9 Å and 20 erg/cm 2 for the {001} wall of MnO. The {110} wall has the width and the energy (1+( J '/ J )) 1/2 times as large as those of the {001} wall, where J and J ' are the coefficients of exchange interaction among <100> and <110> neighbours, respectively. In an ideal crystal, such walls are metastable. When a pair of walls is made to approach each other, a pair recombination takes place, and the stored energy in the wall is released to propagate through the crystal.

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