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.<br/><b>[1] </b>Anomalous Hall effect in noncollinear antiferromagnetic Mn3NiN thin films, D. Boldrin, David; I. Samathrakis, Ilias, J. Zemen et al., Phys. Rev. Materials <b>3 </b>(9) 094409 (2019)<br/><b>[2]</b> The Biaxial Strain Dependence of Magnetic Order in Spin Frustrated Mn3NiN Thin Films, D. Boldrin, F. Johnson, R. Thompson et al., Advanced Functional Materials <b>29 </b>(40) 1902502 (2019)<br/><b>[3] </b>Frustrated magnetism and caloric effects in Mn-based antiperovskite nitrides: Ab initio theory, J. Zemen, E. Mendive-Tapia et al., Phys. Rev.B <b>95</b>,184438, (2017).<br/><b>[4] </b>Room temperature weak collinear ferrimagnet with symmetry driven, large intrinsic magneto-optic and magneto-transport signatures, F. Johnson et al., Phys. Rev. B <b>107</b> (1) (2023)<br/><b>[5] </b>Identifying the octupole antiferromagnetic domain orientation in Mn3NiN by scanning anomalous Nernst effect microscopy, F. Johnson et al., Appl. Phys. Lett. <b>120</b>, 232402 (2022)<br/><b>[6] </b>Giant Piezomagnetism in Mn3NiN, D. Boldrin, A.P. Mihai, Bin Zou, et al., ACS Applied Materials and Interfaces <b>10</b> (22) 18863 (2018)<br/><b>[7] </b>Strain dependence of Berry-phase-induced anomalous Hall effect in the non-collinear antiferromagnet Mn3NiN, F. Johnson et al., Applied Physics Letters <b>119</b> (22) 222401 (2021)