Quenching of the Exchange Bias Training inFe/Cr_2O_3/Fe Trilayer

摘要

Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(1 0 nm)/Cr_2O_3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T=5 K to T=50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T> 200 K up to the highest measured temperature of T=395 K. Remarkably, the latter is far above the bulk Neel temperature T_N=307 K. EB training effects occur only at 5 K < T < 50 K. We show that this training can be quenched by subjecting the system to DC magnetic field, μ_0H_(DC)≤ 7 T. The applied field most likely induces a temperature dependent spin-flop transition. Upon its removal the antiferromagnetic Cr_2O_3 pinning layer evolves uniformly into its quasi-equilibrium spin configuration thus leading to quasi-equilibrium EB.