Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias

Abstract

Rational material design can accelerate the discovery of materials with improved functionalities1. This approach can be implemented in Heusler compounds with tunable magnetic sublattices to demonstrate unprecedented magnetic properties2. Here, we have designed a family of Heusler alloys with a compensated ferrimagnetic state. In the vicinity of the compensation composition in Mn–Pt–Ga, a giant exchange bias (EB) of more than 3 T and a large coercivity are established. The large exchange anisotropy originates from the exchange interaction between the compensated host and ferrimagnetic clusters that arise from intrinsic anti-site disorder. Our design approach is also demonstrated on a second material with a magnetic transition above room temperature, Mn–Fe–Ga, exemplifying the universality of the concept and the feasibility of room-temperature applications. These findings may lead to the development of magneto-electronic devices and rare-earth-free exchange-biased hard magnets, where the second quadrant magnetization can be stabilized by the exchange bias.

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Figure 1: Design of a compensated magnetic state.
Figure 2: Compensated ferrimagnetic state in Mn–Pt–Ga.
Figure 3: Hysteresis loops in Mn–Pt–Ga.
Figure 4: Exchange bias and coercive fields for Mn–Pt–Ga and Mn–Fe–Ga.

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Acknowledgements

We thank J. A. Mydosh and E. Kampert for valuable discussions on the present work. This work was financially supported by the Deutsche Forschungsgemeinschaft DFG (Projects No. TP 1.2-A and No. 2.3-A of Research Unit FOR 1464 ASPIMATT) and by the ERC Advanced Grant No. (291472) ‘Idea Heusler’. We acknowledge the support of the High Magnetic Field Laboratory Dresden (HLD) at HZDR and High Field Magnet Laboratory Nijmegen (HFML-RU/FOM), members of the European Magnetic Field Laboratory (EMFL).

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Correspondence to Ajaya K. Nayak or Claudia Felser.

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Nayak, A., Nicklas, M., Chadov, S. et al. Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias. Nature Mater 14, 679–684 (2015). https://doi.org/10.1038/nmat4248

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