Anisotropy in antiferromagnets

Abstract

Due to the advent of antiferromagnetic (AF) spintronics there is a burgeoning interest in AF materials for a wide range of potential and actual applications. Generally, AFs are characterized via the ordering at the Néel temperature (TN) but, to have a stable AF configuration, it is necessary that the material have a sufficient level of anisotropy so as to maintain the orientation of the given magnetic state fixed in one direction. Unlike the case for ferromagnets there is little established data on the anisotropy of AFs and in particular its origins and those factors which control it. In this paper these factors are reviewed in the light of recent and established experimental data. Additionally, there is no recognized technique for the first principle's determination of the anisotropy of an AF which can only be found indirectly via the exchange bias phenomenon. This technique is reviewed and in particular the implications for the nature of the anisotropy that is measured and its distribution. Finally, a strategy is proposed that would allow for the development of AF materials with controlled anisotropy for future applications.

Competing ferro- and antiferromagnetic exchange drives shape-selective $$\hbox{Co}_3\hbox{O}_4$$ nanomagnetism

“…Through XMCD and magnetometry, it was found that the core of each shape is well described by bulk . As an antiferromagnet, the absence of a net magnetic moment in the core precludes the possibility of shape anisotropy 38 . Thus, any increase in the effective anisotropy comes from the different surface environments such as steps, kinks, and exchange interactions 38 , 39 .…”

First-Principles Calculations of Room-Temperature Antiferromagnetism in Crystalline Transition-Metal Borate Nanosheets: Implications for Spintronics Applications

“…34 2D CrBO 3 with room-temperature magnetism is expected to replace the MnPS 3 as the magnon transport medium in a magnonic transport-based device 11 but may not be appropriate in the read-head devices due to its low anisotropy. 35 Interestingly, the MAE of 2D VBO 3 and MnBO 3 are 1953 and 896 μeV/TM, respectively, which are larger than that of the antiferromagnetic FeAs-III monolayer (820 μeV/TM) 14 and ferromagnetic CrI 3 monolayer (685 μeV/TM) 36 but smaller than that of ferromagnetic α-FeB 3 (4130 μeV/TM). 37 Two-dimensional (2D) VBO 3 and MnBO 3 display high thermal stability due to their very high anisotropy and are promising candidates for read-head devices below room temperature.…”

“…37 Two-dimensional (2D) VBO 3 and MnBO 3 display high thermal stability due to their very high anisotropy and are promising candidates for read-head devices below room temperature. 35 To develop practical spintronic devices working in the ambient environment, the Neél temperature of 2D antiferromagnetic materials should be higher than room temperature. As shown in Figure S2b, there are two sets of sublattices, A-sublattice and B-sublattice, in the nAFM state.…”

“…The long-range antiferromagnetic order may exist in 2D CrBO 3 in view of the investigation of Morpurgo et al that long-range order can persist in MnPS3 monolayers with a smaller MAE (3.5 μeV/atom) . 2D CrBO 3 with room-temperature magnetism is expected to replace the MnPS 3 as the magnon transport medium in a magnonic transport-based device but may not be appropriate in the read-head devices due to its low anisotropy . Interestingly, the MAE of 2D VBO 3 and MnBO 3 are 1953 and 896 μeV/TM, respectively, which are larger than that of the antiferromagnetic FeAs-III monolayer (820 μeV/TM) and ferromagnetic CrI 3 monolayer (685 μeV/TM) but smaller than that of ferromagnetic α-FeB 3 (4130 μeV/TM) .…”

Magnetically switchable spin wave retarder with $90^\circ$ antiferromagnetic domain wall

“…Indeed, the logic functions of present magnetic devices are mostly realized by the trivial existence/absence states of magnetic textures [31][32][33][34] . A promising candidate with intrinsic reprogrammability is the 90 • domain wall with multiple variants in cubic anisotropic materials including RbMnF 3 [35][36][37] , NiO [38][39][40][41] , Mn 3 Pt 42,43 , Heusler alloys 44,45 , etc. The 90 • domain wall has been studied both experimentally and theoretically, including spin wave guiding 17 and refraction 46 , and the domain wall motion driven by electric current 14 or spin-orbit field 47,48 .…”