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

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.