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Abstract Magnetic high entropy alloys (HEAs) consisting of 3dtransition metals offer an exciting platform to explore novel magnetic phases as they often house competing exchange interactions in combination with random site disorders. In this work, a sensitive and tunable magnetic order is demonstrated in sputtered single‐layer FeCoNiMnAlxfilms, as a function of non‐magnetic Al addition, along with an unexpected exchange bias effect. Thin films of 50 nm FeCoNiMn exhibit a face‐centered‐cubic (fcc) phase, reentrant spin glass (SG) transition near 100 K, and a large exchange bias of over 500 Oe after field‐cooling to 5 K. The exchange bias is increased to 930 Oe through a small addition of 5 at.% Al. Further Al addition to 12 at.% results in a body‐centered‐cubic (bcc) phase, coinciding with a large increase in the saturation magnetization, decrease of exchange bias to 50 Oe, and suppression of SG behavior. The change in magnetic order across the Al‐induced structural transformation is mediated by the switching of Mn ground state from AF to FM, which is supported by first‐principles calculations and experimentally confirmed via X‐ray magnetic circular dichroism. These results open up new HEA strategies for explorations of novel magnetic phases.
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A room temperature exchange bias effect caused by the coexisting martensitic phase structures in Ni50Mn38Sb12−xGax polycrystalline Heusler alloys
The exchange bias effect is the physical cornerstone of applications, such as spin valves, ultra-high-density data storage, and magnetic tunnel junctions. This work studied the room temperature exchange bias effect by constructing a Ni50Mn38Sb12−xGax alloy system with coexisting martensitic phase structures. The study found that the exchange bias effect shows a non-monotonic change with the variation of Ga composition at 300 K, and an obvious room temperature exchange bias effect appears in the alloys with coexisting phase structures of 4O and L10, which is due to the strong exchange coupling between ferromagnetic and antiferromagnetic. Further research on the exchange bias effect and temperature shows that the blocking temperature is 420 K, and the exchange bias can stably exist in a temperature range of ∼200 K around room temperature. This work provides a method to engineer exchange bias effects at room temperature.
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- Award ID(s):
- 1834750
- PAR ID:
- 10491753
- Publisher / Repository:
- AIP Publishing LLC
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 123
- Issue:
- 23
- ISSN:
- 0003-6951
- Page Range / eLocation ID:
- 232402
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0178839
