Chiral Magnetism and High-Temperature Skyrmions in B20-Ordered Co-Si

Authors

• Balamurugan Balasubramanian, University of Nebraska - LincolnFollow
• Priyanka Manchanda, Howard University
• Rabindra Pahari, University of Nebraska - LincolnFollow
• Zhen Chen, Cornell University
• Wenyong Zhang, University of Nebraska - Lincoln
• Shah R. Valloppilly, University of Nebraska - LincolnFollow
• Xingzhong Li, University of Nebraska-LincolnFollow
• Anandakumar Sarella, University of Nebraska - LincolnFollow
• Lanping Yue, University of Nebraska - LincolnFollow
• Ahsan Ullah, University of Nebraska - LincolnFollow
• Pratibha Dev, Howard University
• David A. Muller, Cornell University
• Ralph Skomski, University of Nebraska-LincolnFollow
• George C. Hadjipanayis, University of Delware
• David J. Sellmyer, University of Nebraska - LincolnFollow

ORCID IDs

Balamurugan Balasubramanian

Rabindra Pahari

Zhen Chen

Anandakumar Sarella

Lanping Yue

Ahsan Ullah

Document Type

Article

Date of this Version

2020

Citation

PHYSICAL REVIEW LETTERS 124, 057201 (2020)

Comments

© 2020 American Physical Society

DOI: 10.1103/PhysRevLett.124.057201

Abstract

Magnets with chiral crystal structures and helical spin structures have recently attracted much attention as potential spin-electronics materials, but their relatively low magnetic-ordering temperatures are a disadvantage. While cobalt has long been recognized as an element that promotes high-temperature magnetic ordering, most Co-rich alloys are achiral and exhibit collinear rather than helimagnetic order. Crystallographically, the B20-ordered compound CoSi is an exception due to its chiral structure, but it does not exhibit any kind of magnetic order. Here, we use nonequilibrium processing to produce B20-ordered Co_1+xSi_1−x with a maximum Co solubility of x = 0.043. Above a critical excess-Co content (x_c = 0.028), the alloys are magnetically ordered, and for x = 0.043, a critical temperature T_c = 328 K is obtained, the highest among all B20-type magnets. The crystal structure of the alloy supports spin spirals caused by Dzyaloshinskii-Moriya interactions, and from magnetic measurements we estimate that the spirals have a periodicity of about 17 nm. Our density-functional calculations explain the combination of high magnetic- ordering temperature and short periodicity in terms of a quantum phase transition where excess-cobalt spins are coupled through the host matrix.