Magnetic ordering and spin wave dynamics in transition metal arsenides

Karigerasi, Manohar H.

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https://hdl.handle.net/2142/110409 Copy

Description

Title

Magnetic ordering and spin wave dynamics in transition metal arsenides

Author(s)

Karigerasi, Manohar H.

Issue Date

2021-01-28

Director of Research (if dissertation) or Advisor (if thesis)

Shoemaker, Daniel P

Doctoral Committee Chair(s)

Shoemaker, Daniel P

Committee Member(s)

• Cahill, David G
• Zuo, Jian-Min
• MacDougall, Gregory J

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• magnetic ordering
• magnon spectra
• metallic antiferromagnets
• spintronics
• exchange interactions
• magnetic anisotropy
• neutron diffraction
• inelastic neutron scattering
• x-ray diffraction
• calorimetry
• magnetometry
• materials synthesis

Abstract

Ever since spin orbit torque based switching was proposed in antiferromagnets, there is a growing interest in using a metallic antiferromagnet as an active component of a spintronic device. Arsenic forms a large pool of magnetic metals in combination with transition metal atoms. In this report, we explore compounds in Cu-Mn-As phase space by identifying the transition temperatures using calorimetry and magnetometry measurements, understanding the magnetic structure at different temperatures using neutron powder diffraction techniques, and using inelastic neutron scattering techniques to characterize exchange interactions in these materials. We discover a new ternary metallic arsenide Cu0.82Mn1.18As which crystallizes in the hexagonal crystal system and contains a frustrated in-plane triangular arrangement of Mn spins. We also identify the two-step transition in Mn3As2 from a paramagnet to a collinear ferrimagnet and then, into a canted spin state. Using high resolution synchrotron x-ray diffraction and neutron powder diffraction measurements, we identify magnetically coupled structural transitions in tetragonal CuMnAs which result from exchange frustration between the Mn moments and finite Cu moments. Finally, using single crystal inelastic neutron scattering measurements, we determine exchange interactions in Fe2As (same structure as CuMnAs) and show that it has a highly two dimensional magnon character although the phonon interactions are three dimensional in nature.

Graduation Semester

2021-05

Type of Resource

Thesis

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http://hdl.handle.net/2142/110409

Copyright and License Information

Copyright 2021 Manohar H. Karigerasi

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