Magnetic ordering and spin wave dynamics in transition metal arsenides

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Karigerasi, Manohar H.

Contributors dc:contributor

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

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

Statement dc:rights

• Copyright 2021 Manohar H. Karigerasi

Language dc:language

en

Handle dc:identifier

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

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/110409