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Bending strain tailored exchange bias in epitaxial NiMn/γ′-Fe4N bilayers

Research paper by Xiaohui Shi, Wenbo Mi, Qiang Zhang, Xixiang Zhang

Indexed on: 04 Oct '20Published on: 28 Sep '20Published in: Applied physics letters



Abstract

Applied Physics Letters, Volume 117, Issue 13, September 2020. The strain tunable exchange bias has attracted much attention due to its practical applications in flexible and wearable spintronic devices. Here, the flexible epitaxial NiMn/γ′-Fe4N bilayers are deposited by facing-target reactive sputtering. The maximum strain-induced change ratios of exchange bias field HEB and coercivity HC ( ΔHEB/HEB and ΔHC/HC ) are 51% and 22%, respectively. A large strain-induced ΔHEB/HEB appears in a thicker ferromagnetic layer, but a large ΔHC/HC ) appears in a thinner ferromagnetic layer. At a compressive strain, the antiferromagnetic anisotropy of the tetragonal NiMn layer increases, resulting in an increased HC of NiMn/γ′-Fe4N bilayers. The bending-strain induced changes of anisotropy magnetoresistance and planar Hall resistance are also observed at low magnetic fields. The bending-strain tailored magnetic properties can be ascribed to the distributions of ferromagnetic and antiferromagnetic anisotropies.