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oai:figshare.com:article/32641161 2026-10-01T16:25:31Z portal_1172 item_type_8 month_year_10_2026

Investigation on the suitability of IrMn based Antiferromagnetic structures for tunnelling anisotropic magnetoresistance (TAMR) applications Benjamin William Wilson (24169833) PUREID: 640056080 magnetism data storage neutron reflectometry dichorism antiferromagnetism material science <div>Tunnelling Anisotropic Magnetoresistance (TAMR) effect in Antiferromagnet (AFM) based Magnetic Tunnel Junctions (MTJs) was first demonstrated over a decade ago. TAMR results from the change in the energy of states near the Fermi level in a thin metallic AFM film, due to rotation of the Néel vector with respect to the crystal lattice, leading to a change in magnetoresistance through the MgO tunnel barrier. The achievement of room temperature TAMR has important industrial potential, particularly for data storage applications. If successful, it would allow for the creation of a hard disk drive (HDD) reader with only one FM layer, thus dramatically improving its linear resolution, and HDD areal density capacity (ADC).</div><div><br></div><div><div>The main objective of this project is to explore the suitability of Ir₂₀Mn₈₀ based structures for room temperature TAMR applications. The project has investigated numerous fabrication parameters such as seed layers, composition, deposition power and Ar flow rates which impacts the magnetic and structural properties of the structures.</div><div><br></div><div><div>Coercivity enhancement is observed from standard magnetisation measurements in very thin Ir₂₀Mn₈₀ layers (2nm) despite no corresponding exchange bias at room temperature which means the Ir₂₀Mn₈₀ layer starts to reverse with the FM layer before exchange bias is observed at 4nm. The utilisation of X-ray Magnetic Linear Dichroism (XMLD) was essential as it is the only direct probe to determine whether the AFM lattice is rotating and thus determining if Co₇₀Fe₃₀/Ir₂₀Mn₈₀ is suitable for room temperature TAMR. Unfortunately, no reversal of the AFM sublattices for the thinnest Ir₂₀Mn₈₀ layer was observed upon performing XMLD along the hysteresis loop of the Mn L_2,3 edges.</div><div><br></div><div><div>If a reversal of the AFM sublattices were observed, then there would have been a systematic change of the intensity of the XMLD signal when describing the hysteresis loop of the sample. As there was no correlation established between the XMLD intensity change and the hysteresis loop of the samples, this must be due to the polycrystallinity of the samples and the complex non-collinear magnetic structure of the disordered 𝛾 − 𝐼𝑟𝑀𝑛₃. This ultimately shows that this structure and/or the disordered 𝛾 − 𝐼𝑟𝑀𝑛₃ are not suitable for room temperature TAMR applications.</div><div><br></div><div><i>Thesis is embargoed until 31 July 2030</i>.</div><div></div></div></div></div> 2026-10-01T16:25:31Z Text Thesis 10.17034/32641161.v1 https://figshare.com/articles/thesis/Investigation_on_the_suitability_of_IrMn_based_Antiferromagnetic_structures_for_tunnelling_anisotropic_magnetoresistance_TAMR_applications/32641161 All Rights Reserved Open Access after 2030-07-31