Spin-flop transition scenario in finite layered antiferromagnets

A spin-flop ( SF) transition in a finite magnetically uniaxial layered antiferromagnet with an even number of exchange-coupled layers is analytically described in detail. The presence of boundaries in an antiferromagnet at the SF transition results not in the origination of some surface spin-flop ( SSF) phase but in the formation of a 180 degrees domain wall in the middle of the antiferromagnet. This wall at first broadens at further growth of the magnetic field and then splits into two 90 degrees walls, among which a certain SF phase originates and grows in volume. These walls grow apart with field growth until they reach the antiferromagnet boundaries where their pinning occurs. It is at this stage of the system evolution in the magnetic field that a non-uniform state forms which can be considered as a SSF phase. (c) 2006 Elsevier B.V. All rights reserved.