Lebing Chen, a Rice University graduate student, used a high temperature furnace to create chromium triiodide crystallines. These crystals were then used as 2D materials in Oak Ridge National Laboratory's Spallation Neutron Source experiments. Credit: Jeff Fitlow/Rice University
Rice physicists confirmed the topological origins for magnons. They were magnetic features that they found three years ago in a 2D substance. This material could be used to encode information in spins of electrons.
This discovery was made in a paper published online in the American Physical Society journal Physical Review X. It provides a new understanding about topology-driven spin excitations within materials known as 2D Van der Waals magnets. These materials are attracting increasing interest from spintronics. This is a movement within the solid-state electronic community towards technologies that use electron spinning to encode information for computations, storage, and communications.
The quantum objects that contain spin are intrinsically magnetized.
Pengcheng Dai (rice physicist) was co-corresponding author on the Physical Review X Study. He said that inelastic neutron scattering experiments on 2D material chromium Triiodine confirmed that the topological nature, or magnons of spin excitations were found in the material by his group and others in 2018.
Dai stated that the latest Oak Ridge National Laboratory (ORNL) Spallation Neutron Source experiments showed that spin-orbit coupling causes asymmetric interactions among spins of electrons in chromium Triiodine. "The electron spins experience the magnetic field of moving nuclei differently and this impacts their topological excitations," Dai said.
Lebing Chen, a Rice University graduate student displays the chromium triiodide crystallines he created in his Rice University laboratory. The unusual magnetic and electronic properties of stacks of 2D atomically thin chromium triiodide crystals could be useful in technologies that encode information within the spins of electrons. Credit: Jeff Fitlow/Rice University
Van der Waals materials have atomically thin layers of 2D that are stacked in the same way as pages in a book. Although layers have tightly bonded atoms, the bonds between layers is weak. These materials can be used to explore unusual electronic and magnetic behavior. A single 2D layer of chromium triiodine chromium triiodine is magnetic in the same way that magnetic decals stick on a metal fridge. Stacks with three or more 2D layers have the same magnetic order. Physics calls this ferromagnetic. Two stacked sheets of chromium triiodine chromium triiodine also have the antiferromagnetic order.
Dai and his colleagues were intrigued by the strange behavior of the material. Lebing Chen, a Rice graduate student, is the main author of this week’s Physical Review X and the 2018 study. He developed methods to align sheets of chromium Triiodide for ORNL experiments. Chen, Dai, and their colleagues were able to discern the unusual behaviors and features of the material by bombarding them with neutrons.
The researchers previously demonstrated that chromium triiodine creates its own magnetic field through magnons, which move so fast it feels like they are moving with no resistance. Dai stated that the new study has revealed why two layers of 2-D chromium triiodide have antiferromagnetic orders.
Dai stated that they found evidence of a stacking dependent magnetic order in the material. It is crucial to discover the origins of this state and identify key features, as it may exist in other 2D van der Waals magnetics.
Bin Gao of Rice and Jae-Ho Chung of Korea University are additional co-authors.
More information: Lebing Ch et al. Magnetic Field Effect On Topological Spin Excitations In CrI3, Physical Review X (2021). Information from the Journal: Physical Review X, Magnetic Field Effect of Topological Spin Excitations In CrI3, (2021). DOI: 10.1103/PhysRevX.11.031047
