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Title: Machine learning-accelerated discovery of iron cobalt phosphides as rare-earth-free magnets

Journal Article · · Physical Review Materials
ORCiD logo [1];  [2];  [3]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [6];  [2];  [2];  [7]
  1. Univ. of Texas, Austin, TX (United States); Ames Laboratory (AMES), Ames, IA (United States)
  2. Iowa State Univ., Ames, IA (United States); Ames Laboratory (AMES), Ames, IA (United States)
  3. Univ. of Texas, Austin, TX (United States); Univ. of Tokyo, Kashiwa (Japan)
  4. Yantai University (China)
  5. Iowa State Univ., Ames, IA (United States); Zhejiang Agriculture and Forestry University, Zhuji (China)
  6. Guangdong University of Technology, Guangzhou (China)
  7. Univ. of Texas, Austin, TX (United States)

Here, the discovery of rare-earth-free permanent magnets has been a goal of scientists for decades. The absence of rare-earth elements will alleviate a pressing concern about the availability of rare-earth elements used in permanent magnets. These magnets are crucial for applications such as wind turbines, electric cars, and memory devices. Rare-earth magnets are special owing to a large magnetic anisotropy energy (K1). In contrast, iron cobalt phosphides hold promise since doping P into cubic FeCo can induce anisotropy, leading to a large coercivity, without introducing rare-earth elements. We present a comprehensive search over the Fe-Co-P ternary space for magnets, utilizing recently developed adaptive machine learning feedback to efficiently screen over 850 000 structures. We focus on machine learning acceleration as a paradigm for materials design. Further adaptive genetic algorithm searches and first-principles calculations aid in the identification of 16 new structures below the known convex hull. Five of them possess high magnetic polarization (Js > 1 T). The structures with desirable magnetic properties center on (Fe,Co)2⁢P. This supports conventional wisdom, which focuses on the mixture of the two known end compounds: Fe2⁢P and Co2⁢P. Our work provides guidance for synthesis. We find Fe7⁢CoP4 shows the most promise (Js = 1.03T and K1 = 0.83MJ/m3).

Research Organization:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); Welch Foundation
Grant/Contract Number:
AC02-07CH11358
OSTI ID:
2477809
Report Number(s):
AL-J--646
Journal Information:
Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 10 Vol. 8; ISSN 2475-9953
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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