MAGNETIC CONFINEMENT OF REPELLING BLOCH WALLS

In a ferromagnet with orthorhombic magneto-crystalline anisotropy, two repelling 180-degrees domain walls (pi kinks) can be pushed together to form a 360-degrees domain wall (2pi kink) by applying a magnetic field in the easy direction. We show that such a magnetically confined static 360-degrees plane domain wall with Bloch-like structure, connecting two semi-infinite domains with parallel spin orientation, is linearly stable only below a critical strength B(c) of the applied field. At B = B(c) it becomes unstable with respect to a mode with spin component along the hard direction.