Experiments visualize temperature-driven spatial change of magnetic patterns at atomic scale

Experiments led by a gaggle of Boston College researchers enabled atomic scale visualization of a temperature-driven spatial change of magnetic patterns in a Mott insulator, the group has reported in Science Advances.

Today’s forefront supplies are sometimes “lumpy” on the nanoscale: Their digital and magnetic properties fluctuate on size scales down to some nanometers, stated Boston College Associate Professor of Physics Ilija Zeljkovic.

This “inhomogeneity” could be particularly pronounced close to a phase transition, the place the fabric modifications, or transitions, into a distinct phase of matter, stated Zeljkovic, who carried out the challenge with Boston College Professor of Physics Ziqiang Wang, current doctoral recipient He Zhao, and collaborators from the University of California, Santa Barbara.

A very intriguing transition includes a non-magnetic materials that turns into magnetic, Zeljkovic added. This transition could be achieved by cooling the fabric to low temperature, or by tuning its elemental composition. Though important progress has been made in understanding magnetic materials as a complete, little or no is thought in regards to the atomic-scale nature of magnetic transitions.

The researchers studied a bulk single crystal of iridium oxide, Sr₃Ir₂O₇, by which they launched lanthanum as a partial substitute for strontium (Sr) with the intention to carry the system near the antiferromagnetic transition, the group reported in an article titled “Imaging antiferromagnetic domain fluctuations and the effect of atomic-scale disorder in a doped spin-orbit Mott insulator.”

Antiferromagnetism is an uncommon sort of magnetism in a cloth, Zeljkovic stated, which occurs when electron spins at neighboring atomic websites are aligned precisely in reverse instructions. The group stories it used spin-polarized scanning tunneling microscopy (SP-STM) to map the native energy of antiferromagnetic ordering on nanometer size scales.

The researchers found a dramatic re-arrangement of magnetic domains with thermal biking.

“For example, some regions of the sample that were magnetic would become non-magnetic, and vice versa, some areas that used to be non-magnetic would become magnetically ordered after thermal cycling,” Zeljkovic stated. “We also found that magnetic domains locally ‘avoid’ lanthanum substitutions, and tend to form away from these impurities.”

The group employed a statistical evaluation methodology referred to as cluster evaluation idea to investigate the dimensions and distribution of the domains, which may provide insights into whether or not or not the domains are fully randomly distributed, Zeljkovic stated.

“We found that the domains are not randomly distributed, which means that electronic correlations, or electron-electron interactions, likely play a significant role in the emergence of domains,” Zeljkovic stated.

The work constructed upon earlier analysis, the place Zeljkovic and colleagues visualized antiferromagnetic patches, or domains, in a associated doped Mott insulator, Sr₂IrO₄.

“We wanted to investigate what sets the size and the spatial distribution of these domains in Sr₃Ir₂O₇,” Zeljkovic stated. “In addition, we set to explore if and how the domains will change if the material is warmed up to become non-magnetic, and cooled back down into its magnetically ordered state.”

Based on the latest findings, Zeljkovic stated subsequent steps within the analysis will search to broaden this method to different advanced oxides, in addition to supplies with several types of magnetic states, corresponding to ferromagnetism.