Surface spin-flop transition in a uniaxial antiferromagnetic Fe/Cr superlattice induced by a magnetic field of arbitrary direction

Abstract

We studied the transition between the antiferromagnetic and the surface spin-flop phases of a uniaxial antiferromagnetic [Fe(14 Å)/Cr(11 Å]${}_{x20}$ superlattice. For external fields applied parallel to the in-plane easy axis, the layer-by-layer configuration, calculated in the framework of a mean-field one-dimensional model, was benchmarked against published polarized neutron reflectivity data. For an in-plane field $H$ applied at an angle $\psi \ne 0$ with the easy axis, magnetometry shows that the magnetization $M$ vanishes at H=0, then increases slowly with increasing $H$. At a critical value of $H$, a finite jump in $M(H)$ is observed for $\psi <5^{\mathrm{o}}$, while a smooth increase of $M$ $vs$ $H$ is found for $\psi >5^{\mathrm{o}}$. A dramatic increase in the full width at half maximum of the magnetic susceptibility is observed for $\psi \ge 5^{\mathrm{o}}$. The phase diagram obtained from micromagnetic calculations displays a first-order transition to a surface spin-flop phase for low $\psi$ values, while the transition becomes continuous for $\psi$ greater than a critical angle, ${\psi }_{\max }\approx 4.75^{\mathrm{o}}$. This is in fair agreement with the experimentally observed results.

24 pages, 7 figures

References in corpus (1)

• Two-dimensional anisotropic Heisenberg antiferromagnet in a field

Cited by in corpus (1)

• Biconical structures in two-dimensional anisotropic Heisenberg antiferromagnets