Controlling the exchange interaction using the spin-flip transition of antiferromagnetic spins in Ni$_{81}$Fe$_{19}$ / $\alpha$-Fe$_2$O$_3$

TL;DR

This study demonstrates how the exchange interaction in NiFe/α-Fe₂O₃ heterostructures can be controlled through AF spin-flip transitions and annealing, revealing a reversible temperature-induced spin reorientation effect.

Contribution

It introduces the novel use of temperature-induced AF spin reorientation to reversibly control exchange interaction in ferromagnet/antiferromagnet systems.

Findings

AF spin configurations enable strong uniaxial anisotropy and coercivity.

Annealing in magnetic fields can tune coercivity and exchange bias.

Reversible temperature-induced AF spin reorientation controls exchange interaction.

Abstract

We report studies of exchange bias and coercivity in ferromagnetic Ni$_{81}$Fe$_{19}$ layers coupled to antiferromagnetic (AF) (0001), (11$\bar{2}$0), and (11$\bar{0}$2) $\alpha$-Fe$_2$O$_3$ layers. We show that AF spin configurations which permit spin-flop coupling give rise to a strong uniaxial anisotropy and hence a large coercivity, and that by annealing in magnetic fields parallel to specific directions in the AF we can control either coercivity or exchange bias. In particular, we show for the first time that a reversible temperature-induced spin reorientation in the AF can be used to control the exchange interaction.