Magnetic and electron transport properties of Co₂Si nanomagnets

Authors

Balamurugan Balasubramanian, University of Nebraska-Lincoln
Tom A. George, University of Nebraska-Lincoln
Priyanka Manchanda, Howard University
Rabindra Pahari, University of Nebraska-Lincoln
Ahsan Ullah, University of Nebraska - LincolnFollow
Ralph Skomski, University of Nebraska-Lincoln
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2-5-2021

Citation

Balamurugan Balasubramanian et al. PHYSICAL REVIEW MATERIALS 5, 024402 (2021). DOI: 10.1103/PhysRevMaterials.5.024402

Comments

Used by permission.

Abstract

Magnetotransport and ferromagnetism in thin films of Co₂Si nanoclusters are investigated experimentally and theoretically. The nanoclusters are fabricated by an inert-gas condensation-type cluster-deposition method and have an average size of 11.3 nm. Unlike the bulk Co₂Si that exhibits a very weak net magnetic moment only below 10 K, the nanoclusters exhibit room-temperature ferromagnetism with a substantial saturation magnetization. Key features of the system are its closeness to the Stoner transition, magnetic moments induced by spin polarization starting from surface atoms, and nonuniaxial anisotropy associated with the orthorhombic crystal structure of Co₂Si. A method is introduced to determine the effective anisotropy using the experimental magnetization data of this complex system and its relationship with the two lowest-order nonuniaxial anisotropy constants. On decreasing temperature from 300 K, the nanoclusters show electron-transport properties unusual for a ferromagnetic metal, including an increase of Hall resistivity and a nonmonotonic change of negative magnetoresistance with a peak at around 100 K. The underlying physics is explained on the basis of the large polarization of surface spins and variation in the degree of their misalignments due to temperature-dependent effective anisotropy.