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Title:Magnetic ordering and spin wave dynamics in transition metal arsenides
Author(s):Karigerasi, Manohar H.
Director of Research:Shoemaker, Daniel P
Doctoral Committee Chair(s):Shoemaker, Daniel P
Doctoral Committee Member(s):Cahill, David G; Zuo, Jian-Min; MacDougall, Gregory J
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):magnetic ordering
magnon spectra
metallic antiferromagnets
exchange interactions
magnetic anisotropy
neutron diffraction
inelastic neutron scattering
x-ray diffraction
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.
Issue Date:2021-01-28
Rights Information:Copyright 2021 Manohar H. Karigerasi
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05

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