Enhanced exchange bias in MnN/CoFe bilayers after high-temperature annealing

Abstract

We report an exchange bias of more than 2700 Oe at room temperature in MnN/CoFe bilayers after hightemperature annealing. We studied the dependence of exchange bias on the annealing temperature for different MnN thicknesses in detail and found that samples with t MnN > 32 nm show an increase of exchange bias for annealing temperatures higher than T A = 400 • C. Maximum exchange bias values exceeding 2000 Oe with reasonably small coercive fields around 600 Oe are achieved for t MnN = 42, 48 nm. The median blocking temperature of those systems is determined to be 180 • C after initial annealing at T A = 525 • C. X-ray diffraction measurements and Auger depth profiling show that the large increase of exchange bias after hightemperature annealing is accompanied by strong nitrogen diffusion into the Ta buffer layer of the stacks.

Spin-orbit torque induced electrical switching of antiferromagnetic MnN

“…However, the spin orientation is controversial and might depend critically on the lattice constants. In previous studies, some of the authors of this article have shown its utility for exchange bias applications with large exchange bias fields at room temperature [22][23][24][25][26][27]. However, the critical thickness for the onset of exchange bias was observed to be around 10 nm at room temperature, leading to the conclusion that MnN has a small magnetocrystalline anisotropy energy density [22].…”

Recent Developments on MnN for Spintronic Applications

“…However, further work is required for the optimization of the growth conditions of this alloy. For instance, controlling the N/Ar mixture during deposition can result in loop shifts in excess of 2.7 kOe at room temperature and an enhanced thermal stability and median blocking temperature >450 K for compositionally identical structures [17]. A critical difference between the behavior of MnN and IrMn is that the peak in the loop shift as a function of t AF occurs at much lower thicknesses (~8 nm) for the latter.…”

“…However, further work is required for the optimization of the growth conditions of this alloy. For instance, controlling the N/Ar mixture during deposition can result in loop shifts in excess of 2.7 kOe at room temperature and an enhanced thermal stability and median blocking temperature > 450 K for compositionally identical structures [17].…”

Antiferromagnetic thickness and temperature dependence of the exchange bias properties of Co/IrMn nanodots and continuous films: A Monte Carlo study

“…It should be noted that most of the theoretical models for EB properties do not account for thermal effects [5][6][7][8][9]. Recently, many experimental studies were conducted to well understand the thermal effects on the EB properties and they have shown some common behaviors of EB properties and some contradictory behaviors [10][11][12][13][14][15][16][17]. The main common behavior is that the exchange field HE and the coercive field HC decrease as the temperature increases at low temperatures.…”