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

• Main Authors: M. Dunz, J. Schmalhorst, M. Meinert
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2018-05-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.5006551

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