Non-Collinear Mn3NiN Antiferromagnets

Antiferromagnets (AFM) hold interest because of their potential for application in high density, high speed spintronic devices, as an active layer and also as a component in superconducting S/AFM/S Josephson Junctions. Frustrated non-collinear antiferromagnets offer additional attractive functional properties due to their magnetic space group symmetry. Stimulated by these predictions we embarked on a growth program of non collinear antiferromagnetic antiperovskite Mn3NiN films on various perovskite substrates by pulsed laser deposition. We have used observation of the anomalous Hall effect [1] to piece together the experimental phase diagram of magnetic order with biaxial strain [2]. Theory predicts that compressively strained films should support a high temperature collinear ferrimagnetic phase [3]. We use polar MOKE spectroscopy which in combination with DFT calculations sheds light on the origin of the magneto-optical signal as the material evolves from antiferromagnetic to ferrimagnetic phase [4]. Employing a laser scanning technique to create an out-of-plane temperature gradient we can also use the anomalous Nernst effect to provide information about domain structure in our films [5]. Finally, I will review the evidence for piezomagnetism [6,7] predicted to exist in these materials and as time allows, our recent work on the role of piezomagnetism in films grown on highly mismatched substrates.
[1] Anomalous Hall effect in noncollinear antiferromagnetic Mn3NiN thin films, D. Boldrin, David; I. Samathrakis, Ilias, J. Zemen et al., Phys. Rev. Materials 3 (9) 094409 (2019)
[2] The Biaxial Strain Dependence of Magnetic Order in Spin Frustrated Mn3NiN Thin Films, D. Boldrin, F. Johnson, R. Thompson et al., Advanced Functional Materials 29 (40) 1902502 (2019)
[3] Frustrated magnetism and caloric effects in Mn-based antiperovskite nitrides: Ab initio theory, J. Zemen, E. Mendive-Tapia et al., Phys. Rev.B 95,184438, (2017).
[4] Room temperature weak collinear ferrimagnet with symmetry driven, large intrinsic magneto-optic and magneto-transport signatures, F. Johnson et al., Phys. Rev. B 107 (1) (2023)
[5] Identifying the octupole antiferromagnetic domain orientation in Mn3NiN by scanning anomalous Nernst effect microscopy, F. Johnson et al., Appl. Phys. Lett. 120, 232402 (2022)
[6] Giant Piezomagnetism in Mn3NiN, D. Boldrin, A.P. Mihai, Bin Zou, et al., ACS Applied Materials and Interfaces 10 (22) 18863 (2018)
[7] Strain dependence of Berry-phase-induced anomalous Hall effect in the non-collinear antiferromagnet Mn3NiN, F. Johnson et al., Applied Physics Letters 119 (22) 222401 (2021)